Next Article in Journal
Study on Extraction Performance of Vanadium (V) from Aqueous Solution by Octyl-Imidazole Ionic Liquids Extractants
Previous Article in Journal
Enhanced Absorption Performance of Dye-Sensitized Solar Cell with Composite Materials and Bilayer Structure of Nanorods and Nanospheres
Previous Article in Special Issue
Strengthening Mechanisms of Aluminum Matrix Nanocomposites Reinforced with CNTs Produced by Powder Metallurgy
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Metals
Volume 12
Issue 5
10.3390/met12050853
metals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Combining Heat Treatment and High-Pressure Torsion to Enhance the Hardness and Corrosion Resistance of A356 Alloy

by
Mohamed Abdelgawad Gebril
1,*,
Mohd Zaidi Omar
2,
Intan Fadhlina Mohamed
2,
Norinsan Kamil Othman
3 and
Osama M. Irfan
4,5,*
1
Department of Mechanical Engineering, Faculty of Engineering, Benghazi University, Benghazi 16063, Libya
2
Department of Mechanical and Manufacturing Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Malaysia
3
Department of applied physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Malaysia
4
Department of Mechanical Engineering, College of Engineering, Qassim University, Buraydah 51452, Saudi Arabia
5
Mechanical Department, Beni Suef University, Beni Suef 62746, Egypt
*
Authors to whom correspondence should be addressed.
Metals 2022, 12(5), 853; https://0-doi-org.brum.beds.ac.uk/10.3390/met12050853
Submission received: 21 March 2022 / Revised: 6 May 2022 / Accepted: 12 May 2022 / Published: 17 May 2022
(This article belongs to the Special Issue Strengthening Mechanisms of Metals and Alloys)
Browse Figures
Versions Notes

Abstract

:
A356 aluminium alloy is subjected to heat treatment and high-pressure torsion (HPT) processing to investigate the impact of the combined treatments on the alloy’s microstructure refinement, corrosion resistance and hardness. The high-pressure torsion process was performed at room temperature for 0.75 and 5 turns. Subjecting the A356 Al alloy to a heat treatment and subsequent HPT processing produced a more refined microstructure, which has the effect of enhancing the alloy hardness and corrosion resistance under fragmentation and the homogenous redistribution of the intermetallic compounds and the Si particles. The results of the treatment show that there is a marked increase in hardness when imposing a strain from 61 HV to 198 HV on the A356 Al alloy, which has been HPTed and heat-treated for five turns. The polarisation curves show that there is a considerable improvement in the corrosion resistance rate of the alloy from 0.043 mm·year−1 for the A356 Al alloy sample to 0.003 mm·year−1 after five turns of HPT. In this work, the microstructure refinement resulted in the improvement of both the mechanical strength and corrosion resistance of the aluminium 356 alloy after heat treatment in comparison to the untreated alloy.

1. Introduction

Aluminium alloys are lightweight materials that are used in the automotive and aerospace industries instead of cast iron and steel. Because of their desirable properties, such as excellent castability, high strength, high thermal conductivity, low thermal expansion coefficient and good corrosion resistance, Al-Si cast alloys (300 series) are increasingly used in the manufacturing of engine components, such as pistons, cylinder heads, engine blocks and crankcases [1,2,3]. The cast alloy A356 Al is widely utilised in the manufacture of automotive powertrain components. For its propensity to improve castability, Si is a primary alloying element in the A356 Al alloy. However, because of its low solubility in aluminium, it precipitates as coarse flakes with sharp edges, compromising the alloy’s mechanical characteristics [1,4,5,6,7]. The microstructure of these casting alloys is dominated by α-Al dendrites surrounded by eutectic Si particles in the form of platelets or flakes, as well as some intermetallic phases, such as Fe-intermetallic phases, Mg2Si and Al2Cu.
The size, distribution and shape of the eutectic mixture components affect the mechanical properties of the alloys [8,9]. Within an aluminium matrix, Si and intermetallic compounds display cathodic behaviour, resulting in the development of micro-galvanic couples [10,11,12,13]. Pitting corrosion resistance can be improved by lowering the area ratio of Fe-intermetallic compounds and noble Si particles to a less noble Al matrix. In other words, a lower cathode to anode area ratio (Ac/Aa) lowers the corrosion current density and makes it easier to produce a protective layer [14,15]. The heat treatment of A356 Al alloy can be used to modify the eutectic Si particle and the morphology of various intermetallic compounds in order to improve the corrosion resistance by reducing micro-galvanic action [11,16,17] and increase the strength of the alloy by precipitating Mg2Si particles [18].
High-pressure torsion has been shown to be one of the most effective severe plastic deformation processes for achieving a more refined grain structure in a range of alloys [19,20,21,22,23,24,25]. Several studies have shown that the HPT process improves the mechanical properties of aluminium alloys [26,27,28], while other have looked into the impact of grain refinement on the corrosion performance of aluminium alloys [29,30,31,32,33,34,35]. However, there is little agreement on whether the HPT technique can improve the corrosion performance of Al-7Si-3.89Cu-3Ni [36], Al-Fe system [37] and Al-4 Si wt.% [38].
Furthermore, there is a scarcity of studies on the effects of combining heat treatment with the refining process and severe plastic deformation. Nguyen et al. [39] investigated the effect of Al-6wt.% Si to a combination of annealing heat treatment and cooling slope prior to processing by equal channel angular pressing (ECAP) on the hardness and wear resistance of the alloy. The hardness of semi-solid cast ECAP samples improved as a result of the findings. The effect of combining ECAP processing with heat treatment in improving the corrosion resistance of 6061 Al alloy was investigated by Nejadseyfi et al. [40]. The results showed that the ECAP process created a shallow and uniform corroded surface. Natori et al. [41] studied the effect of combining a semi-solid and the ECAP method on Al-7.14Si-0.4 Mg (wt.%) and the mechanical properties that formed. The research revealed that combining semi-solid casting with the ECAP process resulted in Si particle refinement, primary phase grain refinement and a reduction in the hardness difference between the primary phase and the eutectic phase. Several severe plastic deformation methods, including as ECAP and accumulative roll bonding [42,43,44,45], can be used to refine microstructures. The T6 heat treatment combined with high pressure torsion (HPT) can be an effective approach for obtaining highly refined microstructures [40]. However, little research has been conducted on the interaction of these two processes and, as a result, they have consequences on microstructure and corrosion resistance.
The effects of T6 heat treatment and subsequent HPT on the microstructure, hardness and corrosion resistance of A356 Al cast alloy are investigated in this work. This research is significant because it clarifies the impact of the heat treatment performed to change the form of flaky silicon particles prior to refinement by using severe plastic deformation processes.

2. Materials and Methods

The material used in this study was a commercial A356 Al-7Si-0.178Ti-0.126Fe-0.149Mg-0.01Cu-0.006Zn-0.002Mn-0.001Cr (wt.%) with initial ingot dimensions of 80 × 40 × 140 mm (width–thickness–length). The materials were supplied by Vistec Technology Services Sdn Bhd in the form of ingots and pieces. The specimens were prepared for T6 treatment, which was accomplished at 535 °C for 8 h, and then the samples were quenched in water. Following this, the samples were further aged at 180 °C for 3 h [46]. A wire-cutting electrical discharge machine (EDM) was used to cut the A356 Al alloy samples into rod shapes with a 10 mm diameter, and the rods were then sliced into disks with a 1 mm thickness. The applied pressure was 6.0 GPa with a 1 rpm rotation speed in the HPT process, which was carried out at room temperature for 0.75 and 5 turns. A field emission scanning electron microscope (FESEM, Zeiss, Oberkochen, Germany), a field emission transmission electron microscope (FETEM, JEOL, JEM-2100F, Tokyo, Japan) and an optical microscope were used to study the microstructure of the samples (OM, Olympus Corporation, Tokyo, Japan). A microhardness tester (Zwick, Germany; ZHV) was used to measure the microhardness with an applied load of 100 g and a dwell time of 15 s. Indentations were made in the eight radial directions, with each indentation having an equal distance from the centre of the disk to the edge of the disk, as shown in Figure 1. The measurements were taken as the average of three samples per case, and indentations were made in the eight radial directions, with each indentation having an equal distance from the centre of the disk to the edge of the disk, as shown in Figure 1.
The as-cast A356 Al alloy samples and HPT disks were ground with a silicon carbide paper (SiC) with grits ranging from 180 to 1200 before being polished to a mirror-like surface with 1 m of diamond paste before being evaluated for microstructure (Al2O3). The sample was then dipped for 15 s in a Keller solution, rinsed under running water, and dried by using a blower. The microstructure of the disks was assessed both in the centre and at the edges. To quantify the grain size, a quantitative metallography study was performed in accordance with ASTM E112. The width and length of the Si particles were measured using the Smart Tiffv2 software, with at least 220 particles considered in each case. The corrosion test was carried out at room temperature with a GAMRY 3.2 potentiostat in a naturally aerated 3.5 percent NaCl electrolyte solution in order to mimic a seawater environment [11,12]. After approximately 15 min of immersion in 3.5 percent NaCl, the potentiodynamic test was performed.
To analyse the surface appearance of the sample, immersion tests were carried out for ten days in a 3.5 wt. percent NaCl natural aerated solution. Each sample was adhered on a piece of epoxy that had been air-dried for 24 h. Before conducting each corrosion test, the samples were ground with up to 1200-grit SiC.

3. Results and Discussion

3.1. Microstructure Pre- and Post-Heat Treatment

Figure 2a depicts optical micrographs of an A356 Al alloy sample containing a dendritic-shaped primary α-Al phase surrounded by a coarse eutectic mixture. The dendritic primary grain is approximately 172 µm with a coarse Si particle. Figure 2b shows the enlarged morphology of a flake-like shape with sharp edges. Figure 2c shows the characteristics of the microstructure after the T6 heat treatment of the A356 Al alloy. The flaky Si particles were transformed into angular- to spherical-shaped crystals and showed the presence of intermetallic compounds after the application of the T6 solution heat treatment.

3.2. HPTed Microstructure after 0.75 Turn Pre- and Post-T6

Figure 3 shows the optical micrographs of the centre and the edge of the HPTed A356 Al alloy sample pre- and post-T6 after 0.75 turn.
These images were taken at two different locations: (a,c) were taken at the centre of the disk and (b,d) were taken close to the edge of the disk, as shown in Figure 3. The large primary α-Al phase grain size can be observed at the centre of the A356 Al alloy specimen, while the primary α-Al phase with the longitudinal shape can be seen at the edge of the sample due to applied strain. The size of the α-Al phase decreases at the disk edge under the imposed strain, as shown in Figure 3a,b. The original large and coarse A356 Al alloy primary α-Al phase and low shear strain imposed through 0.75 turn contribute to retention of the large α-Al phase in the A356 Al alloy sample. The Si particles are heterogeneously distributed in the Al matrix of the A356 Al alloy. Figure 3c,d shows the microstructure of the HPTed heat-treated A356 Al alloy after 0.75 turn. The Si particles at the edge of the heat-treated A356 Al alloy are heterogeneously distributed.

3.3. HPTed Microstructure after Five Turns Pre- and Post-T6

Figure 4 shows the mapping of the centre and the edge of the HPTed A356 Al alloy pre-T6 after five turns. In the HPT processing of the A356 Al alloy samples, the primary α-Al phase can be observed at the centre of the disk as shown in Figure 4a. The grain boundaries of α-Al phase are non-obviously at the edge due to the greater shear resulting from the higher number of turns; this produced the homogeneously and uniformly distributed Si particles shown in Figure 4b. Figure 4b shows the presence of relatively large eutectic Si particles at the edge of the disk of the A356 Al alloy. The eutectic Si particles are homogeneous within the aluminium matrix in the A356 Al alloy sample. The Si particles are fragmented into significantly smaller sizes.
Figure 5 shows the mapping of the centre and edge of the HPTed heat-treated A356 Al alloy sample under an applied pressure of 6.0 GPa after five turns. The samples subjected to the combined heat treatment and HPT process causes the fragmentation of the Si particles due to the high strain imposed on them. The fraction of small Si particles is considerably higher, and the microstructure is more homogeneously distributed. This is consistent with the findings made by [47]. The eutectic Si particles are more homogenously distributed in the heat-treated samples than in the untreated samples. The edges of the processed samples have a finer microstructure than the centre of the samples as a result of the greater torsional strain during the HPT process as shown in Figure 5b.
Figure 6 shows the mapping of the Si particles and intermetallic compounds at the centre and the edge of the HPTed heat-treated A356 Al alloy sample. The initial flaky Si particles in the A356 Al alloy sample are no longer present after processing, and the extensive breakage of the Si phases and intermetallic phases can be observed after the T6 heat treatment that was followed by high compression pressure and strain. These results indicate that the sample subjected to heat treatment before HPT processing has a strong effect on the size and dispersion of the large silicon particles after processing.
The imposition of higher strains on the A356 Al alloy during the HPT process via increased rotational turns causes the breakdown of the intermetallic compounds and the Si particles in the A356 Al alloy. This process, in consequence, reduces the average of the Si particles size and the homogeneous dispersion of the eutectic phase. The T6 heat treatment and the subsequent HPT process produced a more refined Si particle due to the fragmentation process that occurred during heat treatment as well as to the higher torsional straining during the HPT process.

3.4. Hardness of the HPT of the A356 Al Alloy Pre- and Post-T6

Figure 7 shows the average Vickers microhardness across the diameter of each A356 Al alloy sample pre/post T6 via HPT under 6.0 GPa through 0.75 and 5 turns. The difference in hardness was determined along the diameter of the disk with a constant 0.5 mm separation between each processed disk. A significant increase in the hardness of the A356 Al alloy is noted after the HPT process, although it should be emphasised that the increase in hardness at the edge of the disk is more pronounced than in the centre. Applying the HPT process to the A356 Al alloy significantly increases its initial hardness. The values of hardness are low in the centre of the disk at the beginning of the deformation, but increase with the increase in the applied strain. The variation in hardness is dependent upon the number of turns and the position from the centre to the edge of the disk. The increase in hardness is more apparent after 5 turns, in contrast to 0.75, and is more apparent through the centre to the edge. The figure also shows that the edge of the disk shows a homogeneous distribution of hardness values after 5 HPT, which causes enhanced hardness. After the heat treatment, brittle Si particles were broken up and turned into spheroids, which made them stronger and harder [48,49]. Moreover, with the increased number of HPT turns, the error bar of the average microhardness for the HPTed heat-treated A356 Al alloy sample became smaller, which indicates that the microstructural homogeneity of the HPTed heat-treated A356 Al alloy samples is further enhanced through more HPT revolutions. This outcome is consistent with the microstructure observed in Figure 3, Figure 4, Figure 5 and Figure 6, which shows that the eutectic Si particles and intermetallic compounds in the sample processed through 5 turns are smaller and more uniformly distributed than the sample subjected to a 0.75 turn of HPT processing. The hardness of the A356 Al alloy sample increased after 0.75 and 5 turns after being subjected to heat treatment and the subsequent HPT. The increase in hardness can be ascribed to the fragmentation and redistribution of both eutectic Si and intermetallic compounds, the increased dislocation density and the grain refinement resulting from the high strain induced during HPT processing. As mentioned above, a higher number of revolutions in the HPT process generate significant shear stress associated with a high dislocation density, which could be attributed to grain refinement as shown in Figure 8 and greater microhardness [26,47,50,51,52]. The combined T6 heat treatment and HPT processing resulted in the refinement of Si particles.

3.5. Corrosion Resistance of the HPTed A356 Al Alloy

3.5.1. Surface Morphology

Figure 9 shows the top and side view micrograph of the HPTed A356 Al alloy pre- and post-heat treatment. Figure 9a shows the surface micrograph of the A356 Al alloy before HPT processing, while Figure 9b shows the surface micrograph of the HPTed A356 Al alloy sample after five turns and immersion for ten days in 3.5% NaCl solution. The corrosion generally spread along with the eutectic phase as a result of localised corrosion, while the silicon particles and α-Al interface were not affected by the treatment [53,54]. The HPTed heat-treated samples show a smaller size and number of pits as well as the area around the pits than those within the A356 Al alloy sample and the HPT as-cast sample due to the distribution of the smaller cathodic particles after the T6 heat treatment and HPT processing. The presence of an area free of corrosion around the pits indicates that cathodic reaction occurs in the corrosion-free area, while the anodic reaction occurs within the pit due to the concentration of galvanic cells [49,55]. Figure 9b,d shows that, when the heat-treated sample is compared to the A356 Al alloy sample, the processed samples with a higher number of HPT turns have a less pitting surface. The higher number of HPT turns is associated with reduced Si-containing particles in the alloy, while a decrease in the cathodic area causes a decrease in the anodic current density; this eventually results in improved corrosion resistance [56,57].
Figure 9c shows the side view of the pitting corrosion sample of the A356 Al alloy. It is worth noting that the enlarged eutectic mixture phase leads to more extensive surface corrosion of the alloy. This finding indicates that the micro-galvanic cells between the cathodic high Si and Al matrix may contribute to the development of pitting corrosion in the high Si particles area. Figure 9c shows the pitting corrosion of the HPTed heat-treated A356 Al alloy sample after five turns of HPT processing. The difference in the area of the eutectic mixture phase, the depth of corrosion and the spread of eutectic Si particles and intermetallic compounds before and after HPT processing between the A356 Al alloy and HPTed heat-treated A356 Al alloy samples enhanced the corrosion resistance values shown in Figure 9c,d and Table 1. The reduced eutectic phase, as well as the redistribution and homogeneity of the eutectic phase, contribute to the reduction in the corrosion rate of the HPTed combined heat treatment of the A356 Al alloy sample, in contrast to those of the A356 Al alloy before HPT processing. The FESEM and microhardness measurements indicate that there is an apparent evolution in the microstructure homogeneity of the A356 Al alloy samples with higher turn numbers of HPT processing, where the size of Si particles is reduced, the intermetallic particles are broken down and the refined Si and intermetallic particles become more uniformly distributed within the eutectic matrix.

3.5.2. Potentiodynamic Test

Potentiodynamic polarization was carried out to evaluate the impact of eutectic phase refinement and the microstructure homogeneity resulting from HPT processing on the corrosion resistance of the A356 Al alloy. The electrochemical behaviour of the A356 Al alloy was investigated by exposing the samples to a corrosive environment at room temperature using a 3.5% NaCl electrolyte solution [58]. The Tafel extrapolation method was used to measure the rate of corrosion to establish the corrosion resistance of both the A356 Al alloy and the combination of the heat-treated A356 Al alloy and the HPT-processed (HPTed heat-treated) A356 Al alloy samples. Figure 10, which shows the polarization curves of the A356 Al alloy samples before and after HPT processing, is used as a basis to compare the samples. Based on the above curves, the estimated average corrosion potentials of both samples are almost similar, with only minor differences. The results also demonstrate that the lower corrosion rate after a combination of the T6 heat treatment and HPT process may be attributed to the modified shape of Si particles after the T6 heat treatment as well as the grain refinement and redistribution of eutectic phase after HPT processing. These may be associated with a reduced cathodic to anodic ratio. The 0.0424 mm.year−1 corrosion rate of the A356 Al alloy was reduced to 0.00205 mm.year−1 after five turns of HPT. With the fine-grained structure of the α-Al and the eutectic phase, as well as the higher grain boundaries, the concentration of chloride per grain boundary is reduced, lowering the current density [59,60]. This results in the formation of a more stable passive film, which enhances corrosion resistance. The results of this study are consistent with those made by [61,62,63,64]. This results in the formation of a more permanent and intact passivation coating, which improves corrosion resistance.
Metals 12 00853 g010 550
Figure 10. Polarization curves of the A356 Al alloy (as-cast) before and after HPT processing.
Figure 10. Polarization curves of the A356 Al alloy (as-cast) before and after HPT processing.
Metals 12 00853 g010
Table
Table 1. Average of the current density (Icorr), corrosion rate (CR) and polarization resistance (Rp).
Table 1. Average of the current density (Icorr), corrosion rate (CR) and polarization resistance (Rp).
SamplesEcorr (V)Icorr A/cm2Rp (Ω·cm2)Βc (V·Dec−1)Βa (V·Dec−1)CR (mm·Year−1)
As-cast−0.6983.894 × 10−65.212 × 1030.6420.05040.0424
As-cast T6, 0.75 turn−0.7081.021 × 10−62.977 × 1040.4210.03750.012
As-cast T6, 5 turns−0.7102.233 × 10−78.870 × 1040.3320.03540.00295

4. Conclusions

In this study, the effect of microstructural refinement on the corrosion resistance and hardness of the A356 Al alloy processed by a combination of the T6 heat treatment and HPT processing was investigated. The following conclusions were reached:
  • An ultrafine-microstructure hypoeutectic A356 Al alloy with a homogenous distribution of eutectic intermetallic and Si particles was achieved by combining heat treatment and HPT processing through five revolutions at room temperature.
  • The hardness of the hypoeutectic A356 Al alloy was significantly improved with the increasing number of HPT turns.
  • The corrosion resistance of the HPTed heat-treated A356 Al alloy sample was significantly enhanced due to the microstructure refinement and redistribution of the eutectic phase in the Al matrix, which resulted in a reduced galvanic potential difference. The HPTed A356 Al alloy has the lowest current density 2.233 × 10−7 A/cm2, due to the combination of heat treatment and HPT process. The favourable corrosion resistance was attributed to the refined microstructure and the redistribution of the eutectic phase that prevented the occurrences of micro-galvanic cells on the alloy surface’s protective layer.

Author Contributions

M.A.G. carried out the experimental works, analysis and writing under the supervision of M.Z.O., I.F.M., N.K.O. and O.M.I. All authors have read and agreed to the published version of the manuscript.

Funding

The APC was funded by the Deanship of Scientific Research, Qassim University, KSA. (This work was supported in part by GUP-2018-150 grant under Universiti Kebangsaan Malaysia for materials processing in Kyushu University, Japan).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors wish to express their gratitude to the Deanship of scientific Re-search, Qassim University for funding the publication of this work.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Anasyida, A.S.; Daud, A.R.; Ghazali, M.J. Dry sliding wear behaviour of Al-12Si-4Mg alloy with cerium addition. Mater. Des. 2010, 31, 365–374. [Google Scholar] [CrossRef]
  2. Ashiri, R.; Niroumand, B.; Karimzadeh, F. Physical, mechanical and dry sliding wear properties of an Al-Si-Mg-Ni-Cu alloy under different processing conditions. J. Alloys Compd. 2014, 582, 213–222. [Google Scholar] [CrossRef]
  3. Fabrizi, A.; Ferraro, S.; Timelli, G. The influence of Sr, Mg and Cu addition on the microstructural properties of a secondary AlSi9Cu3 (Fe) die casting alloy. Mater. Charact. 2013, 85, 13–25. [Google Scholar] [CrossRef]
  4. Ghazali, M.J.; Rainforth, W.M.; Jones, H. The wear of wrought aluminium alloys under dry sliding conditions. Tribol. Int. 2007, 40, 160–169. [Google Scholar] [CrossRef]
  5. Galvin, E.; O’Brien, D.; Cummins, C.; Mac Donald, B.J.; Lally, C. A strain-mediated corrosion model for bioabsorbable metallic stents. Acta Biomater. 2017, 55, 505–517. [Google Scholar] [CrossRef]
  6. Haghdadi, N.; Zarei-Hanzaki, A.; Abedi, H.R.; Sabokpa, O. The effect of thermomechanical parameters on the eutectic silicon characteristics in a non-modified cast A356 aluminum alloy. Mater. Sci. Eng. A 2012, 549, 93–99. [Google Scholar] [CrossRef]
  7. Harun, M.; Talib, I.A.; Daud, A.R. Effect of element additions on wear property of eutectic aluminium-silicon alloys. Wear 1996, 194, 54–59. [Google Scholar] [CrossRef]
  8. Olofsson, J.; Svensson, I.L.; Lava, P.; Debruyne, D. Characterisation and investigation of local variations in mechanical behaviour in cast aluminium using gradient solidification, Digital Image Correlation and finite element simulation. Mater. Des. 2014, 56, 755–762. [Google Scholar] [CrossRef] [Green Version]
  9. Gebril, M.A.; Omar, M.Z.; Mohamed, I.F.; Othman, N.K. Microstructural Evaluation and Corrosion Resistance of Semisolid Cast A356 Alloy Processed by Equal Channel Angular Pressing. Metals 2019, 9, 303. [Google Scholar] [CrossRef] [Green Version]
  10. Buarzaiga, M.M.; Thorpe, S.J. Corrosion behavior of as-cast, silicon carbide particulate-aluminum alloy metal-matrix composites. Corrosion 1994, 50, 176–185. [Google Scholar] [CrossRef]
  11. Mingo, B.; Arrabal, R.; Pardo, A.; Matykina, E.; Skeldon, P. 3D study of intermetallics and their effect on the corrosion morphology of rheocast aluminium alloy. Mater. Charact. 2016, 112, 122–128. [Google Scholar] [CrossRef]
  12. Arrabal, R.; Mingo, B.; Pardo, A.; Mohedano, M.; Matykina, E.; Rodríguez, I. Pitting corrosion of rheocast A356 aluminium alloy in 3.5 wt.% NaCl solution. Corros. Sci. 2013, 73, 342–355. [Google Scholar] [CrossRef]
  13. Davis, J.R. Aluminum and Aluminum Alloys; ASM International: Material Park, OH, USA, 2001; p. 66. [Google Scholar] [CrossRef]
  14. Tahamtan, S.; Fadavi Boostani, A. Evaluation of pitting corrosion of thixoformed A356 alloy using a simulation model. Trans. Nonferrous Met. Soc. China 2010, 20, 1702–1706. [Google Scholar] [CrossRef]
  15. Tahamtan, S.; Fadavi Boostani, A. Quantitative analysis of pitting corrosion behavior of thixoformed A356 alloy in chloride medium using electrochemical techniques. Mater. Des. 2009, 30, 2483–2489. [Google Scholar] [CrossRef]
  16. Park, C.; Kim, S.; Kwon, Y.; Lee, Y.; Lee, J. Mechanical and corrosion properties of rheocast and low-pressure cast A356-T6 alloy. Mater. Sci. Eng. A 2005, 391, 86–94. [Google Scholar] [CrossRef]
  17. Gebril, M.A.; Omar, M.Z.; Mohamed, I.F.; Othman, N.K.; Abdelgnei, M.A.H. Corrosion Improvement and Microstructure Evaluation of SEM-Solid A356 Alloy by Ecap Process. Proc. J. Phys. Conf. Ser. 2018, 1082, 12110. [Google Scholar] [CrossRef]
  18. Mohamed, A.M.A.; Samuel, F.H. A Review on the Heat Treatment of Al-Si-Cu/Mg Casting Alloys. In Heat Treatment-Conventional and Novel Applications; InTech: Rijeka, Croatia, 2012; pp. 55–72. [Google Scholar] [CrossRef]
  19. Zhilyaev, A.P.; Langdon, T.G. Using high-pressure torsion for metal processing: Fundamentals and applications. Prog. Mater. Sci. 2008, 53, 893–979. [Google Scholar] [CrossRef]
  20. Lee, S.; Edalati, K.; Horita, Z. Microstructures and mechanical properties of pure V and Mo processed by high-pressure torsion. Mater. Trans. 2010, 51, 1072–1079. [Google Scholar] [CrossRef] [Green Version]
  21. Ikoma, Y.; Hayano, K.; Edalati, K.; Saito, K.; Guo, Q.; Horita, Z. Phase transformation and nanograin refinement of silicon by processing through high-pressure torsion. Appl. Phys. Lett. 2012, 101, 121908. [Google Scholar] [CrossRef]
  22. Cubero-Sesin, J.M.; Horita, Z. Powder consolidation of Al-10 wt% Fe alloy by high-pressure torsion. Mater. Sci. Eng. A 2012, 558, 462–471. [Google Scholar] [CrossRef]
  23. Mohamed, I.F.; Masuda, T.; Lee, S.; Edalati, K.; Horita, Z.; Hirosawa, S.; Matsuda, K.; Terada, D.; Omar, M.Z. Strengthening of A2024 alloy by high-pressure torsion and subsequent aging. Mater. Sci. Eng. A 2017, 704, 112–118. [Google Scholar] [CrossRef]
  24. Sha, G.; Tugcu, K.; Liao, X.Z.; Trimby, P.W.; Murashkin, M.; Valiev, R.Z.; Ringer, S.P. Strength, grain refinement and solute nanostructures of an Al--Mg--Si alloy (AA6060) processed by high-pressure torsion. Acta Mater. 2014, 63, 169–179. [Google Scholar] [CrossRef]
  25. Bryła, K.; Morgiel, J.; Faryna, M.; Edalati, K.; Horita, Z. Effect of high-pressure torsion on grain refinement, strength enhancement and uniform ductility of EZ magnesium alloy. Mater. Lett. 2018, 212, 323–326. [Google Scholar] [CrossRef]
  26. El Aal, M.I.A.; Kim, H.S. Wear properties of high pressure torsion processed ultrafine grained Al-7% Si alloy. Mater. Des. 2014, 53, 373–382. [Google Scholar] [CrossRef]
  27. Lee, H.J.; Han, J.K.; Janakiraman, S.; Ahn, B.; Kawasaki, M.; Langdon, T.G. Significance of grain refinement on microstructure and mechanical properties of an Al-3% Mg alloy processed by high-pressure torsion. J. Alloys Compd. 2016, 686, 998–1007. [Google Scholar] [CrossRef] [Green Version]
  28. Sauvage, X.; Lee, S.; Matsuda, K.; Horita, Z. Origin of the influence of Cu or Ag micro-additions on the age hardening behavior of ultrafine-grained Al-Mg-Si alloys. J. Alloys Compd. 2017, 710, 199–204. [Google Scholar] [CrossRef]
  29. Ralston, K.D.; Fabijanic, D.; Birbilis, N. Effect of grain size on corrosion of high purity aluminium. Electrochim. Acta 2011, 56, 1729–1736. [Google Scholar] [CrossRef]
  30. Son, I.; Nakano, H.; Oue, S.; Kobayashi, S.; Fukushima, H.; Horita, Z. Effect of equal-channel angular pressing on pitting corrosion of pure aluminum. Int. J. Corros. 2012, 2012, 450854. [Google Scholar] [CrossRef] [Green Version]
  31. Brunner, J.G.; Birbilis, N.; Ralston, K.D.; Virtanen, S. Impact of ultrafine-grained microstructure on the corrosion of aluminium alloy AA2024. Corros. Sci. 2012, 57, 209–214. [Google Scholar] [CrossRef]
  32. Kumar Singh, A.; Ghosh, S.; Mula, S. Simultaneous improvement of strength, ductility and corrosion resistance of Al2024 alloy processed by cryoforging followed by ageing. Mater. Sci. Eng. A 2016, 651, 774–785. [Google Scholar] [CrossRef]
  33. El-Garhy, G.; El Mahallawy, N.; Shoukry, M.K. Effect of grain refining by cyclic extrusion compression (CEC) of Al-6061 and Al-6061/SiC on wear behavior. J. Mater. Res. Technol. 2021, 12, 1886–1897. [Google Scholar] [CrossRef]
  34. Sakthivel, C.; Kumar, V.S.; Iqbal, U.M. Effects of prior annealing on the mechanical properties of a twist-extruded aa 7075 aluminum alloy. Mater. Tehnol. 2020, 54, 17–23. [Google Scholar] [CrossRef]
  35. Elizalde, S.; Ezequiel, M.; Figueroa, I.A.; Cabrera, J.M.; Braham, C.; Gonzalez, G. Microstructural evolution and mechanical behavior of an al-6061 alloy processed by repetitive corrugation and straightening. Metals 2020, 10, 489. [Google Scholar] [CrossRef] [Green Version]
  36. Wang, X.; Nie, M.; Wang, C.T.; Wang, S.C.; Gao, N. Microhardness and corrosion properties of hypoeutectic Al-7Si alloy processed by high-pressure torsion. Mater. Des. 2015, 83, 193–202. [Google Scholar] [CrossRef]
  37. Nakano, H.; Yamaguchi, H.; Yamada, Y.; Oue, S.; Son, I.; Horita, Z.; Koga, H. Effects of High-Pressure Torsion on the Pitting Corrosion Resistance of Aluminum—Iron Alloys. Mater. Trans. 2013, 54, 1642–1649. [Google Scholar] [CrossRef] [Green Version]
  38. Cubero-Sesin, J.M.; Horita, Z. Strengthening via Microstructure Refinement in Bulk Al-4 mass% Fe Alloy Using High-Pressure Torsion. Mater. Trans. 2012, 53, 46–55. [Google Scholar] [CrossRef] [Green Version]
  39. Nguyen, V.T.; Hussain, Z.; Anasyida, A.S.; Huy, T.D.; Almanar, I.P. Influence of Semi-Solid Casting and Equal Channel Pressing on Microstructure of a Hypoeutectic Al-Si Alloy. In Materials Science Forum; Trans Tech Publications Ltd.: Bäch SZ, Switzerland, 2015; Volume 819, pp. 9–14. [Google Scholar] [CrossRef]
  40. Nejadseyfi, O.; Shokuhfar, A.; Dabiri, A.; Azimi, A. Combining equal-channel angular pressing and heat treatment to obtain enhanced corrosion resistance in 6061 aluminum alloy. J. Alloys Compd. 2015, 648, 912–918. [Google Scholar] [CrossRef]
  41. Natori, K.; Utsunomiya, H.; Tanaka, T. Improvement in formability of semi-solid cast hypoeutectic Al-Si alloys by equal-channel angular pressing. J. Mater. Process. Technol. 2017, 240, 240–248. [Google Scholar] [CrossRef]
  42. Gebril, M.A.; Omar, M.Z.; Othman, N.K.; Mohamed, I.F. Microstructural Refinement and Corrosion Resistance Improvement of Heat-Treated A356 Alloy Processed by Equal Channel Angular Pressing. Sains Malays. 2019, 48, 2749–2757. [Google Scholar] [CrossRef]
  43. Langdon, T.G. The principles of grain refinement in equal-channel angular pressing. Mater. Sci. Eng. A 2007, 462, 3–11. [Google Scholar] [CrossRef]
  44. Saito, Y. Ultra-fine grained bulk aluminum produced by accumulative roll-bonding (ARB) process. Scr. Mater. 1998, 39, 1221–1227. [Google Scholar] [CrossRef]
  45. Łyszkowski, R. Influence of Strain Route Changes on the Microstructure and Mechanical Properties of CuZn36 Alloy during Cross Channel Extrusion CCE. Materials 2022, 15, 1124. [Google Scholar] [CrossRef] [PubMed]
  46. Rooy, E.L.; Linden, J.H.L. Properties and Selection: Nonferrous Alloys and Special-Purpose Materials. In Van ASM Metals Handbook; ASM International: Materials Park, OH, USA, 1990; Volume 2, pp. 3330–3345. [Google Scholar] [CrossRef]
  47. Cepeda-Jiménez, C.M.; García-Infanta, J.M.; Ruano, O.A.; Carreño, F. Mechanical properties at room temperature of an Al-Zn-Mg-Cu alloy processed by equal channel angular pressing. J. Alloys Compd. 2011, 509, 8649–8656. [Google Scholar] [CrossRef] [Green Version]
  48. Zhu, M. Effects of T6 heat treatment on the microstructure, tensile properties, and fracture behavior of the modified A356 alloys. J. Mater. 2017, 36, 243–249. [Google Scholar] [CrossRef]
  49. Möller, H.; Govender, G.; Stumpf, W. Factors influencing tensile mechanical properties of Al-7Si-Mg casting alloys A356/7. In Light Metals 2012; Springer: Cham, Switzerland, 2012; pp. 467–471. [Google Scholar]
  50. Loucif, A.; Figueiredo, R.B.; Baudin, T.; Brisset, F.; Langdon, T.G. Microstructural evolution in an Al-6061 alloy processed by high-pressure torsion. Mater. Sci. Eng. A 2010, 527, 4864–4869. [Google Scholar] [CrossRef]
  51. Nie, M.; Wang, C.T.; Qu, M.; Gao, N.; Wharton, J.A.; Langdon, T.G. The corrosion behaviour of commercial purity titanium processed by high-pressure torsion. J. Mater. Sci. 2014, 49, 2824–2831. [Google Scholar] [CrossRef]
  52. Ghosh, K.S.; Gao, N.; Starink, M.J. Characterisation of high pressure torsion processed 7150 Al-Zn-Mg-Cu alloy. Mater. Sci. Eng. A 2012, 552, 164–171. [Google Scholar] [CrossRef]
  53. Barbucci, A.; Bruzzone, G.; Delucchi, M.; Panizza, M.; Cerisola, G. Breakdown of passivity of aluminium alloys by intermetallic phases in neutral chloride solution. Intermetallics 2000, 8, 305–312. [Google Scholar] [CrossRef]
  54. Goodarzy, M.H.; Arabi, H.; Boutorabi, M.A.; Seyedein, S.H.; Najafabadi, S.H.H. The effects of room temperature ECAP and subsequent aging on mechanical properties of 2024 Al alloy. J. Alloys Compd. 2014, 585, 753–759. [Google Scholar] [CrossRef]
  55. Callister, W.D., Jr.; Rethwisch, D.G. Fundamentals of Materials Science and Engineering: An Integrated Approach; John Wiley & Sons: Hoboken, NJ, USA, 2012. [Google Scholar]
  56. Di Schino, A.; Kenny, J.M. Effects of the grain size on the corrosion behavior of refined AISI 304 austenitic stainless steels. J. Mater. Sci. Lett. 2002, 21, 1631–1634. [Google Scholar] [CrossRef]
  57. Musa, A.Y.; Mohamad, A.B.; Al-Amiery, A.A.; Tien, L.T. Galvanic corrosion of aluminum alloy (Al2024) and copper in 1.0 M hydrochloric acid solution. Korean J. Chem. Eng. 2012, 29, 818–822. [Google Scholar] [CrossRef] [Green Version]
  58. Yahya, S.; Rahim, A.A. Inhibitive Behaviour of Corrosion of Aluminium Alloy in NaCl by Mangrove Tannin. Sains Malays. 2011, 40, 953–957. [Google Scholar]
  59. Inturi, R.B.; Szklarska-Smialowska, Z. Localized corrosion of nanocrystalline 304 type stainless steel films. Corrosion 1992, 48, NACE-92050398. [Google Scholar] [CrossRef]
  60. Rashida, S.; Islamia, N.; Ariffina, A.K.; Ridhab, M.; Fonnab, S. The effect of immersion time on the corrosion behavior of SUS304 in brine using half-cell potential measurement. Polarization 2016, 5, 7. [Google Scholar] [CrossRef] [Green Version]
  61. Krishna, K.G.; Sivaprasad, K.; Narayanan, T.S.N.S.; Kumar, K.C.H. Localized corrosion of an ultrafine grained Al-4Zn-2Mg alloy produced by cryorolling. Corros. Sci. 2012, 60, 82–89. [Google Scholar] [CrossRef]
  62. Akiyama, E.; Zhang, Z.; Watanabe, Y. Effects of severe plastic deformation on the corrosion behavior of aluminum alloys. J. Solid State Electrochem. 2009, 13, 277–282. [Google Scholar] [CrossRef]
  63. Dan, S.; Jiang, J.; Lin, P.; Yang, D. Corrosion behavior of ultra-fine grained industrial pure Al fabricated by ECAP. Trans. Nonferrous Met. Soc. China 2009, 19, 1065–1070. [Google Scholar]
  64. Parfenov, E.V.; Kulyasova, O.B.; Mukaeva, V.R.; Mingo, B.; Farrakhov, R.G.; Cherneikina, Y.V.; Yerokhin, A.; Zheng, Y.F.; Valiev, R.Z. Influence of ultra-fine grain structure on corrosion behaviour of biodegradable Mg-1Ca alloy. Corros. Sci. 2020, 163, 108303. [Google Scholar] [CrossRef]
Metals 12 00853 g001 550
Figure 1. Schematic illustration of the HPT disk and the location of the micrograph, hardness measurement and corrosion area.
Figure 1. Schematic illustration of the HPT disk and the location of the micrograph, hardness measurement and corrosion area.
Metals 12 00853 g001
Metals 12 00853 g002 550
Figure 2. Microstructural features of the A356 Al alloy of (a) as-cast, (b) enlargement of eutectic Si and (c) eutectic Si after T6.
Figure 2. Microstructural features of the A356 Al alloy of (a) as-cast, (b) enlargement of eutectic Si and (c) eutectic Si after T6.
Metals 12 00853 g002
Metals 12 00853 g003 550
Figure 3. Microstructure of the HPTed A356 Al alloy pre-T6 at the (a) centre and (b) edge, and post T6 at (c) centre and (d) the edge by 0.75 turns.
Figure 3. Microstructure of the HPTed A356 Al alloy pre-T6 at the (a) centre and (b) edge, and post T6 at (c) centre and (d) the edge by 0.75 turns.
Metals 12 00853 g003
Metals 12 00853 g004 550
Figure 4. Mapping of the HPTed A356 Al alloy pre-T6 at the (a) centre and (b) edge by 5 turns.
Figure 4. Mapping of the HPTed A356 Al alloy pre-T6 at the (a) centre and (b) edge by 5 turns.
Metals 12 00853 g004
Metals 12 00853 g005 550
Figure 5. Mapping of the HPTed A356 Al alloy post-T6 at the (a) centre and (b) edge by 5 turns.
Figure 5. Mapping of the HPTed A356 Al alloy post-T6 at the (a) centre and (b) edge by 5 turns.
Metals 12 00853 g005
Metals 12 00853 g006 550
Figure 6. Mapping of the HPTed heat-treated as-cast A356 Al alloy (a) at the centre and (b) at the edge and alloying elements at the edge (c) Al, (d) Si, (e) Mg, (f) Fe, (g) Ti and (h) Cu, after 5 turns.
Figure 6. Mapping of the HPTed heat-treated as-cast A356 Al alloy (a) at the centre and (b) at the edge and alloying elements at the edge (c) Al, (d) Si, (e) Mg, (f) Fe, (g) Ti and (h) Cu, after 5 turns.
Metals 12 00853 g006
Metals 12 00853 g007 550
Figure 7. Microhardness plotted against distance from the disk centre of the A356 Al alloy pre-T6 (A-C) and post-T6 heat treatment (H-T, A-C) after 0.75 and 5 turns.
Figure 7. Microhardness plotted against distance from the disk centre of the A356 Al alloy pre-T6 (A-C) and post-T6 heat treatment (H-T, A-C) after 0.75 and 5 turns.
Metals 12 00853 g007
Metals 12 00853 g008 550
Figure 8. TEM ultrafine grains micrograph of the HPTed heat-treated A356 Al alloy sample.
Figure 8. TEM ultrafine grains micrograph of the HPTed heat-treated A356 Al alloy sample.
Metals 12 00853 g008
Metals 12 00853 g009 550
Figure 9. Surface appearance of the (a) A356 Al alloy; (b) HPTed heat-treated A356 Al alloy; side view of the (c) A356 Al alloy and (d) HPTed heat-treated A356 Al alloy after immersion for 10 days.
Figure 9. Surface appearance of the (a) A356 Al alloy; (b) HPTed heat-treated A356 Al alloy; side view of the (c) A356 Al alloy and (d) HPTed heat-treated A356 Al alloy after immersion for 10 days.
Metals 12 00853 g009
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Gebril, M.A.; Omar, M.Z.; Mohamed, I.F.; Othman, N.K.; Irfan, O.M. Combining Heat Treatment and High-Pressure Torsion to Enhance the Hardness and Corrosion Resistance of A356 Alloy. Metals 2022, 12, 853. https://0-doi-org.brum.beds.ac.uk/10.3390/met12050853

AMA Style

Gebril MA, Omar MZ, Mohamed IF, Othman NK, Irfan OM. Combining Heat Treatment and High-Pressure Torsion to Enhance the Hardness and Corrosion Resistance of A356 Alloy. Metals. 2022; 12(5):853. https://0-doi-org.brum.beds.ac.uk/10.3390/met12050853

Chicago/Turabian Style

Gebril, Mohamed Abdelgawad, Mohd Zaidi Omar, Intan Fadhlina Mohamed, Norinsan Kamil Othman, and Osama M. Irfan. 2022. "Combining Heat Treatment and High-Pressure Torsion to Enhance the Hardness and Corrosion Resistance of A356 Alloy" Metals 12, no. 5: 853. https://0-doi-org.brum.beds.ac.uk/10.3390/met12050853

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop