Research on Solution Treatment of Al-12.0Si-4.0Cu-0.7Mg-1.5Ni Alloy
The as-cast Al-12.0Si-4.0Cu-0.7Mg-1.5Ni alloy was treated by two-stage solution+aging.The effects of the second stage solution temperature and solution time in two-stage solution on the microstructure and hardness of the as-cast Al-12.0Si-4.0Cu-0.7Mg-1.5Ni alloy were studied by SEM,XRD and hardness test.The results show that the microstructure of as-cast Al-12.0Si-4.0Cu-0.7Mg-1.5Ni alloy is mainly composed of α-Al solid solution,massive primary Si phase,acicular eutectic Si phase and reticular second phase.After two-stage solution treatment,the massive primary Si phase in the alloy is passivated obviously,the eutectic Si phase is refined obviously,and the reticular second phase is also significantly fragmented.At 490℃×2 h+525℃×4 h,the reticular phase is almost completely fragmented,and the eutectic Si phase is the smallest.With the increase of the second stage solution temperature and solution time in two-stage solution,the hardness of T6 Al-12.0Si-4.0Cu-0.7Mg-1.5Ni alloy increases first and then decreases.The hardness of the alloy treated by 490℃×2 h+525℃×4 h double-stage solution+180℃×6 h aging is the highest,reaching 88.2 HRB.
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