Effect of cryogenic and aging treatment on microstructure and precipitation behavior of rapidly cooled Al-0.3Sc-0.3Zr alloy
A non-equilibrium solidified Al-0.3Sc-0.3Zr alloy was prepared by high vacuum induction melting and copper mold spraying.Effect of cryogenic and aging treatment on microstructure,microhardness and precipitation behavior of the rapidly cooled alloy were studied.The results show that the Sc and Zr elements in the rapidly cooled alloy are basically dissolved into the α-Al matrix,and only a small amount of primary phase is formed.After cryogenic treatment,the stress fragmentation effect leads to significant refinement of the alloy's grains and the appearance of ultra fine recrystallized structure in local region.Aging treatment can effectively promote the precipitation of precipitates in the rapidly cooled and rapidly cooled+cryogenic treated alloy.After aging at 300 ℃ for 70 min,the hardness of the rapidly cooled Al-0.3Sc-0.3Zr alloy increases from the original 32.31 HV0.2 to 74.57 HV0.2.Cryogenic treatment can accelerate the precipitation of Al3(Sc,Zr)phases,shorten the peak aging time at 300 ℃ to 50 min,and achieve a microhardness of 78.09 HV0.2,which is 142％higher than the original rapidly cooled alloy.
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