This study examines the cascade effects of chemical modification, mechanical mold vibration during solidification, and subsequent T6 heat treatment on the microstructural evolution and multi-property enhancement of A356 Alloy cast via permanent mold casting. Initially Sodium (Na) modifying flux (2– 4 wt%) and Strontium (Sr) elemental modifier (0.01–0.05 wt%) were implemented to refine the morphology of eutectic silicon; Sr addition at an optimal concentration of 0.04 wt.% yielded superior eutectic silicon refinement compared to Na. To further refine the microstructure the optimal Sr-modified melt was subjected to mechanical mold vibration at frequencies ranging from 40–60 Hz. (0.5 mm amplitude), with 55 Hz identified as peak frequency for mitigating porosity and grain refinement. Finally, a T6 thermal profile (Solutionizing at 535°C for 1 h, Quenching in water at room temperature, age hardening at 154°C for 5 h and allowing it to cool in normal air) was super imposed onto the optimized Sr + 55 Hz vibration condition. Microstructural characterization via optical and scanning electron microscopy revealed a distinct transition of eutectic silicon from coarse acicular needles to a highly refined, globular morphology, alongside enhanced fragmentation of a α-Al dendrites. This sequential processing approach led to an outstanding concurrent increase in ultimate tensile strength (UTS), yield strength (YS), ductility, Micro–Vicker’s hardness, and Izod impact energy. While simultaneously decreasing porosity and optimizing electrical resistivity. The results demonstrate that combining physical and chemical melt treatments with tailored aging treatments offers a highly effective pathway for manufacturing high-performance aluminum castings.

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1. Comalco Aluminium Ltd. Modification of Foundry Al-Si Alloys. Technical Report No. 4. December 1997.
2. Samuel AM, Doty HW, Valtierra S, Samuel FH. Effect of grain refining and Sr-modification interactions on the impact toughness of Al-Si-Mg cast alloys. Mater Des. 2014;56:264–273.
3. Mohamed AMA, Samuel FH, Alkahtani S. Thermal analysis and microstructures of modified grain-refined Al-7Si-Mg cast alloy. In: Light Metals 2012. Warrendale (PA): The Minerals, Metals & Materials Society; 2012.
4. Samuel AM, Elgallad EM, Samuel FH, et al. On the microstructure, hardness and impact toughness of 356 and 413 alloys. Int J Met. 2017;11:240–254.
5. Farahany S, Ourdjini A, Idris MH, Thai LT. Poisoning effect of bismuth on modification behaviour of strontium in LM25 alloy. Bull Mater Sci. 2011;34(6):1223–1231.
6. Lipiński T. The effect of Na and B exothermic mixtures on the hardness and abrasive wear of the AlSi7Mg alloy. Arch Foundry Eng. 2010;10(4):109–114.
7. Chen Z, Zhang R. Effect of strontium on primary dendrite and eutectic temperature of A357 aluminum alloy. China Foundry. 2010;7(2):149–152.
8. Liao H, Sun Y, Sun G. Restraining effect of strontium on the crystallization of Mg2Si phase during solidification in Al-Si-Mg casting alloys and mechanisms. Mater Sci Eng A. 2003;358:164–170.
9. Prasada Rao AK, Mahfoud M. Effect of cadmium on the microstructure of Al-7Si alloy. J Alloys Compd. 2010;491–L10.
10. Prukkanon W, Srisukhumbowornchai N, Limmaneevichitr C. Modification of hypoeutectic Al-Si alloys with scandium. J Alloys Compd. 2009;477:454–460.
11. Tsai YC, Chou CY, Lee SL, Lin CK, Lin JC, Lim SW. Effect of trace La addition on the microstructures and mechanical properties of A356 (Al-7Si-0.35Mg) aluminum alloys. J Alloys Compd. 2009;487:157–162.
12. Moussa ME, El-Hadad S, Khalifa W. Influence of chemical modification by Y2O3 on eutectic Si characteristics and tensile properties of A356 alloy. Trans Nonferrous Met Soc China. 2019;29:1365–1374.
13. Liao C, Chen J, Li Y, Tu R, Pan C. Morphologies of Al4Sr intermetallic phase and its modification property upon A356 alloys. J Mater Sci Technol. 2012;28(6):524–530.
14. Wu DY, Kang J, Feng ZH, Su R, Liu CH, Li T, et al. Utilizing a novel modifier to realize multi-refinement and optimized heat treatment of A356 alloy. J Alloys Compd. 2019;791:628–640.
15. Özgü TS, Çalın R, Tanış NA. Investigation of the effect of mechanical vibration applied during solidification on the microstructure and properties of aluminum 356 alloy. Arch Foundry Eng. 2024.
16. Yadav S, Tewari SP, Singh JK, Ram SC. Effects of mechanical vibration on the physical, metallurgical and mechanical properties of cast A308 (LM21) aluminium alloy. Int J Miner Metall Mater. 2022;29:1206–1215.
17. Varun S, Tatram K, Chavan. Influence of mould vibration on microstructural behaviour and mechanical properties of LM25 aluminium alloy using gravity die casting process. Mater Today Proc. 2021;46:4412–4418.
18. Kudryashova O, Khmeleva M, Danilov P, Dammer V, Vorozhtsov A, Eskin D. Optimizing the conditions of metal solidification with vibration. Metals. 2019;9:366.
19. Sulaiman S, Zulkifli ZA. Effect of mould vibration on the mechanical properties of aluminium alloy castings. Adv Mater Process Technol. 2018;4(2):335–343.
20. Jiang W, Chen X, Wang B, Fan Z, Wu H. Effects of vibration frequency on microstructure, mechanical properties, and fracture behavior of A356 aluminum alloy obtained by expendable pattern shell casting. Int J Adv Manuf Technol. 2016;83:167–175.
21. Jiang W, Fan Z, Chen X, Wang B, Wu H. Combined effects of mechanical vibration and wall thickness on microstructure and mechanical properties of A356 aluminum alloy produced by expendable pattern shell casting. Mater Sci Eng A. 2014;619:228–237.
22. Limmaneevichitr C, Pongananpanya S, Kajornchaiyakul J. Metallurgical structure of A356 aluminum alloy solidified under mechanical vibration: An investigation of alternative semi-solid casting routes. Mater Des. 2009;30:3925–3930.
23. Taghavi F, Saghafian H, Kharrazi YHK. Study on the effect of prolonged mechanical vibration on the grain refinement and density of A356 aluminum alloy. Mater Des. 2009;30:1604–1610.
24. Taghavi F, Saghafian H, Kharrazi YHK. Study on the ability of mechanical vibration for the production of thixotropic microstructure in A356 aluminum alloy. Mater Des. 2009;30:115–121.
25. Kocatepe K. Effect of low frequency vibration on porosity of LM25 and LM6 alloys. Mater Des. 2007;28:1767–1775.
26. Abu-Dheir N, Khraisheh M, Saito K, Male A. Silicon morphology modification in the eutectic Al-Si alloy using mechanical mold vibration. Mater Sci Eng A. 2005;393:109–117.
27. Baskaran J, Raghuvaran P, Ashwin S. Experimental investigation on the effect of microstructure modifiers and heat treatment influence on A356 alloy. Mater Today Proc. 2021;37(Pt 2):3007–3010.
28. Ernam O, Sekban T, Tugan O, Dizdar K, Sahin H, Dispinar D. Effect of heat treatment on mechanical properties of Er-, Dy-, Eu-modified A356 alloy. In: Light Metals 2022. Cham: Springer; 2022. p. 785–789.
29. Haskel T, Verran GO, Barbieri R, Silva J, Novak D. Effects of strontium addition and T6 heat treatment on uniaxial fatigue of A356 aluminium alloy: Fatigue life and cyclic behaviour. Fatigue Fract Eng Mater Struct. 2022;45:2159–2173.
30. Zhu M, Jian Z, Yang G, Zhou Y. Effects of T6 heat treatment on the microstructure, tensile properties, and fracture behavior of modified A356 alloys. Mater Des. 2012;36:243–249.
31. Rodrigues RA, Costa JCM, Nascimento NR, Oliveira JS, Kieling AC, Cunha JS, et al. Effect of different T6 heat treatment conditions on the microstructure and mechanical properties of Al-7%Si-0.35%Mg (A356) alloy for use in motorcycles. Metals. 2025;15:692.
32. Shabestari SG, Shahri F. Influence of modification, solidification conditions and heat treatment on the microstructure and mechanical properties of A356 aluminum alloy. J Mater Sci. 2004;39:2023–2032.

This study examines the cascade effects of chemical modification, mechanical mold vibration during solidification, and subsequent T6 heat treatment on the microstructural evolution and multi-property enhancement of A356 Alloy cast via permanent mold casting. Initially Sodium (Na) modifying flux (2– 4 wt%) and Strontium (Sr) elemental modifier (0.01–0.05 wt%) were implemented to refine the morphology of eutectic silicon; Sr addition at an optimal concentration of 0.04 wt.% yielded superior eutectic silicon refinement compared to Na. To further refine the microstructure the optimal Sr-modified melt was subjected to mechanical mold vibration at frequencies ranging from 40–60 Hz. (0.5 mm amplitude), with 55 Hz identified as peak frequency for mitigating porosity and grain refinement. Finally, a T6 thermal profile (Solutionizing at 535°C for 1 h, Quenching in water at room temperature, age hardening at 154°C for 5 h and allowing it to cool in normal air) was super imposed onto the optimized Sr + 55 Hz vibration condition. Microstructural characterization via optical and scanning electron microscopy revealed a distinct transition of eutectic silicon from coarse acicular needles to a highly refined, globular morphology, alongside enhanced fragmentation of a α-Al dendrites. This sequential processing approach led to an outstanding concurrent increase in ultimate tensile strength (UTS), yield strength (YS), ductility, Micro–Vicker’s hardness, and Izod impact energy. While simultaneously decreasing porosity and optimizing electrical resistivity. The results demonstrate that combining physical and chemical melt treatments with tailored aging treatments offers a highly effective pathway for manufacturing high-performance aluminum castings.

🔒 This is a subscription article

Full text is available to subscribers and institutional members. Please choose an option below to access it.

1. Comalco Aluminium Ltd. Modification of Foundry Al-Si Alloys. Technical Report No. 4. December 1997.
2. Samuel AM, Doty HW, Valtierra S, Samuel FH. Effect of grain refining and Sr-modification interactions on the impact toughness of Al-Si-Mg cast alloys. Mater Des. 2014;56:264–273.
3. Mohamed AMA, Samuel FH, Alkahtani S. Thermal analysis and microstructures of modified grain-refined Al-7Si-Mg cast alloy. In: Light Metals 2012. Warrendale (PA): The Minerals, Metals & Materials Society; 2012.
4. Samuel AM, Elgallad EM, Samuel FH, et al. On the microstructure, hardness and impact toughness of 356 and 413 alloys. Int J Met. 2017;11:240–254.
5. Farahany S, Ourdjini A, Idris MH, Thai LT. Poisoning effect of bismuth on modification behaviour of strontium in LM25 alloy. Bull Mater Sci. 2011;34(6):1223–1231.
6. Lipiński T. The effect of Na and B exothermic mixtures on the hardness and abrasive wear of the AlSi7Mg alloy. Arch Foundry Eng. 2010;10(4):109–114.
7. Chen Z, Zhang R. Effect of strontium on primary dendrite and eutectic temperature of A357 aluminum alloy. China Foundry. 2010;7(2):149–152.
8. Liao H, Sun Y, Sun G. Restraining effect of strontium on the crystallization of Mg2Si phase during solidification in Al-Si-Mg casting alloys and mechanisms. Mater Sci Eng A. 2003;358:164–170.
9. Prasada Rao AK, Mahfoud M. Effect of cadmium on the microstructure of Al-7Si alloy. J Alloys Compd. 2010;491–L10.
10. Prukkanon W, Srisukhumbowornchai N, Limmaneevichitr C. Modification of hypoeutectic Al-Si alloys with scandium. J Alloys Compd. 2009;477:454–460.
11. Tsai YC, Chou CY, Lee SL, Lin CK, Lin JC, Lim SW. Effect of trace La addition on the microstructures and mechanical properties of A356 (Al-7Si-0.35Mg) aluminum alloys. J Alloys Compd. 2009;487:157–162.
12. Moussa ME, El-Hadad S, Khalifa W. Influence of chemical modification by Y2O3 on eutectic Si characteristics and tensile properties of A356 alloy. Trans Nonferrous Met Soc China. 2019;29:1365–1374.
13. Liao C, Chen J, Li Y, Tu R, Pan C. Morphologies of Al4Sr intermetallic phase and its modification property upon A356 alloys. J Mater Sci Technol. 2012;28(6):524–530.
14. Wu DY, Kang J, Feng ZH, Su R, Liu CH, Li T, et al. Utilizing a novel modifier to realize multi-refinement and optimized heat treatment of A356 alloy. J Alloys Compd. 2019;791:628–640.
15. Özgü TS, Çalın R, Tanış NA. Investigation of the effect of mechanical vibration applied during solidification on the microstructure and properties of aluminum 356 alloy. Arch Foundry Eng. 2024.
16. Yadav S, Tewari SP, Singh JK, Ram SC. Effects of mechanical vibration on the physical, metallurgical and mechanical properties of cast A308 (LM21) aluminium alloy. Int J Miner Metall Mater. 2022;29:1206–1215.
17. Varun S, Tatram K, Chavan. Influence of mould vibration on microstructural behaviour and mechanical properties of LM25 aluminium alloy using gravity die casting process. Mater Today Proc. 2021;46:4412–4418.
18. Kudryashova O, Khmeleva M, Danilov P, Dammer V, Vorozhtsov A, Eskin D. Optimizing the conditions of metal solidification with vibration. Metals. 2019;9:366.
19. Sulaiman S, Zulkifli ZA. Effect of mould vibration on the mechanical properties of aluminium alloy castings. Adv Mater Process Technol. 2018;4(2):335–343.
20. Jiang W, Chen X, Wang B, Fan Z, Wu H. Effects of vibration frequency on microstructure, mechanical properties, and fracture behavior of A356 aluminum alloy obtained by expendable pattern shell casting. Int J Adv Manuf Technol. 2016;83:167–175.
21. Jiang W, Fan Z, Chen X, Wang B, Wu H. Combined effects of mechanical vibration and wall thickness on microstructure and mechanical properties of A356 aluminum alloy produced by expendable pattern shell casting. Mater Sci Eng A. 2014;619:228–237.
22. Limmaneevichitr C, Pongananpanya S, Kajornchaiyakul J. Metallurgical structure of A356 aluminum alloy solidified under mechanical vibration: An investigation of alternative semi-solid casting routes. Mater Des. 2009;30:3925–3930.
23. Taghavi F, Saghafian H, Kharrazi YHK. Study on the effect of prolonged mechanical vibration on the grain refinement and density of A356 aluminum alloy. Mater Des. 2009;30:1604–1610.
24. Taghavi F, Saghafian H, Kharrazi YHK. Study on the ability of mechanical vibration for the production of thixotropic microstructure in A356 aluminum alloy. Mater Des. 2009;30:115–121.
25. Kocatepe K. Effect of low frequency vibration on porosity of LM25 and LM6 alloys. Mater Des. 2007;28:1767–1775.
26. Abu-Dheir N, Khraisheh M, Saito K, Male A. Silicon morphology modification in the eutectic Al-Si alloy using mechanical mold vibration. Mater Sci Eng A. 2005;393:109–117.
27. Baskaran J, Raghuvaran P, Ashwin S. Experimental investigation on the effect of microstructure modifiers and heat treatment influence on A356 alloy. Mater Today Proc. 2021;37(Pt 2):3007–3010.
28. Ernam O, Sekban T, Tugan O, Dizdar K, Sahin H, Dispinar D. Effect of heat treatment on mechanical properties of Er-, Dy-, Eu-modified A356 alloy. In: Light Metals 2022. Cham: Springer; 2022. p. 785–789.
29. Haskel T, Verran GO, Barbieri R, Silva J, Novak D. Effects of strontium addition and T6 heat treatment on uniaxial fatigue of A356 aluminium alloy: Fatigue life and cyclic behaviour. Fatigue Fract Eng Mater Struct. 2022;45:2159–2173.
30. Zhu M, Jian Z, Yang G, Zhou Y. Effects of T6 heat treatment on the microstructure, tensile properties, and fracture behavior of modified A356 alloys. Mater Des. 2012;36:243–249.
31. Rodrigues RA, Costa JCM, Nascimento NR, Oliveira JS, Kieling AC, Cunha JS, et al. Effect of different T6 heat treatment conditions on the microstructure and mechanical properties of Al-7%Si-0.35%Mg (A356) alloy for use in motorcycles. Metals. 2025;15:692.
32. Shabestari SG, Shahri F. Influence of modification, solidification conditions and heat treatment on the microstructure and mechanical properties of A356 aluminum alloy. J Mater Sci. 2004;39:2023–2032.