HOT DEFORMATION BEHAVIOR OF SiCW/ AZ91 MAGNESIUMMATRIX COMPOSITE AND AZ91 ALLOY
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摘要: 利用Gleeble-1500 对SiCW/ AZ91 复合材料和AZ91 镁合金在温度为423～723 K、应变速率为0.002～0.25s-1 、最大应变量为60 %的条件下进行高温压缩变形行为的研究。测试了其真应力-应变曲线, 观察了变形后的显微组织。结果表明: 晶须的转动和折断导致复合材料的应变软化现象较合金明显; 复合材料和合金的应变速率敏感指数(m) 和表观激活能(Q) 均随温度的升高而增大; 晶须的加入细化了晶粒, 使复合材料的m 值比合金高; 同时晶须的加入也限制了位错交滑移和晶界的迁移, 因此复合材料的Q 值比合金高; 压缩变形过程中, 合金和复合材料发生了动态回复和动态再结晶。Abstract: High temperature compressive deformation of SiCW/ AZ91 composite and unreinforced AZ91 magnesiumalloy was performed using Gleeble-1500 thermal simulator in the range of deformation temperature f rom 423 to723 K, st rain rate f rom 0.002 to 0.25 s -1 and maximum deformation st rain of 60 %. The compressive t rue st resst rue st rain curves were measured and hot deformation microst ructures were observed. St rain sof tening behavior ofcomposite is more obvious than that of unreinforced alloy because of the rotation and breakage of whiskers duringcompression. The st rain rate sensitivity exponent ( m) and apparent activation energy (Q) of both the SiCW/ AZ91composite and AZ91 alloy increase with the increasing of temperature. The higher m value of the composite is considered to be resulted f rom the fine microst ructure due to the addition of SiC whiskers. The addition of whisker limit s the cross slip of dislocations and migration of grain boundary, which causes Q value of the composite higher thanthat of the unreinforced alloy. During the compression, dynamic recovery and dynamic recrystallization occur in boththe unreinforced alloy and SiCW/ AZ91 composite.
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