Second-Phase Precipitates and Their Influence on Mechanical and Work Hardening Behavior of Mg-Al-Sn Alloy

Mg-5Al-5Sn (AT55) alloy was subjected to hot extrusion, followed by aging treatments at 150 °C. Microstructural study confirms the grain refinement by extrusion, whereas aging results in the nucleation and growth of secondary phase (Mg17Al12). Micro-hardness of hot extruded specimen ranges from 85 ± 4 to 62 ± 3 Hv after solutionizing and substantially increases to 114 ± 2 Hv after 256 h of aging. Both yield and ultimate tensile strength have improved after aging, by 9 and 14%, respectively. The extruded alloy shows the yield plateau, while in other conditions (peak-aged and over-aged), the yield plateaus are almost negligible. The high ductility of the solutionized is related to their high work hardening ability, which increases initially and subsequently decreases during peak-aged and over-aged conditions. The solutionized alloy exhibits highest work-hardening capacity (1.01) and strain hardening exponent (0.452). Numerous uniformly distributed, lead to detrimental for work hardening rate and hence lower ductility under peak-aged and over-aged conditions