往复挤压ZK60合金的低温准超塑性(英文)

通过2道次往复挤压制备细晶ZK60合金,在443~523K和初始应变速率为3.310-4~3.310-2s-1的范围内测试合金的低温超塑性。结果表明:往复挤压ZK60合金的平均晶粒尺寸约为5.0m,分布于基体内的破碎二次相颗粒和沉淀颗粒尺寸分别为不大于175nm和50nm。该合金具有低温准超塑性,在523K和3.310-4s-1应变速率下伸长率最大,为270%;在443和473K时,应变速率敏感系数m小于0.2;在523K时m为0.42。当温度不高于473K和523K时,超塑性变形激活能分别不高于63.2kJ/mol和110.6kJ/mol。当低于473K时,主要的超塑性流变机制为晶内滑移;在523K时,主要的超塑性变形机制为晶界滑移,由晶界扩散控制的位错蠕变为主要的兼容机制。

Low temperature quasi-superplasticity of ZK60 alloy prepared by reciprocating extrusion

Fine-grained ZK60 alloy was prepared by 2-pass reciprocating extrusion,and the low temperature superplasticity was conducted in a temperature range from 443 to 523 K and an initial strain rate ranging from 3.3×10-4 to 3.3×10-2 s-1.The results show that the alloy has an equiaxed grain structure with an average grain size of about 5.0 μm,and the sizes of broken secondary particles and precipitates are no more than 175 and 50 nm,respectively.The alloy exhibits quasi-superplasticity with a maximum elongation of 270% at 523 K and an initial strain rate of 3.3×10-4 s-1.The strain rate sensitivity m is less than 0.2 at 443 and 473 K,and it is 0.42 at 523 K.The apparent activation energies at temperature below 473 K and at 523 K are less than 63.2 and 110.6 kJ/mol,respectively.At temperature below 473 K,mainly intragranular sliding contributes to superplastic flow.At 523 K,grain boundary sliding is the dominant deformation mechanism,and dislocation creep controlled by grain boundary diffusion is considered to be the main accommodation mechanism.