PROCESSING-DEPENDENT WORK HARDENING AND AGEING RESPONSE OF AZ91, AJ63 AND AE44 MAGNESIUM ALLOYS
Keywords:
Magnesium alloys, AZ91, AJ63, AE44, Solution treatment, Rolling deformation, Ageing hardening, Vickers hardness, Work hardeningAbstract
Magnesium alloys are attractive lightweight structural materials, but their limited room-temperature hardness and deformation resistance require strengthening through heat treatment and plastic deformation. This study systematically compared the processing responses of three cast magnesium alloys, AZ91, AJ63 and AE44, under identical laboratory conditions. As-cast bars were subjected to solution treatment at 410 °C for 24 h, rolling deformation, ageing at 175 °C for 2-72 h, and combined solutionising-rolling-ageing routes. Vickers hardness was measured using a 2 kg load. Optical micrographs were used to relate hardness evolution to phase morphology and deformation behaviour. Solution treatment alone produced no statistically significant hardness increase in any alloy. AZ91 showed the strongest strengthening response: direct rolling produced hardness above 76 HV in the low-strain range, and the combined route of solutionising, 15% rolling and ageing for 18 h increased hardness to approximately 82.4 HV. AJ63 was highly sensitive to brittle cracking in the as-cast condition; effective work hardening was only obtained after solutionising, with hardness rising to approximately 62-63 HV after rolling and ageing. AE44 showed a weaker ageing response, but rolling continuously increased hardness to approximately 50-51 HV at around 13% strain. The results demonstrate strong composition-dependent processing behaviour. AZ91 benefits most from strain-assisted ageing, AJ63 requires solution treatment before rolling, and AE44 is better strengthened by controlled deformation than by solution treatment alone.References
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