快速凝固/粉末冶金技术制备挤压态AZ91合金热加工性能研究

Thermal Processing Performance Study of Extruded AZ91 Alloy Prepared by Rapid Solidification/Powder Metallurgy

摘要:

对快速凝固粉末冶金制备的挤压AZ91镁合金，在温度为250—400 ℃、应变速率范围为0.01—1 s^-1下进行了热压缩变形试验。同时，利用热加工图分析评价了合金的热加工特性。结果表明：合金的流变应力，随变形温度的升高或应变速率的减小而减小；同时，基于双曲正弦关系建立了描述流变应力行为的本构方程，RS/PM制备的AZ91挤压合金的热变形机制为晶格扩散控制的位错蠕变；通过微观组织验证了动态再结晶和流变失稳行为，当温度高于350 ℃、应变速率在0.01—0.1 s^-1时，合金的可加工性最佳。

Abstract:

In this paper， hot compression deformation tests were conducted on extruded AZ91 magnesium alloy prepared by Rapidly Solidified/Powder metallurgy （RS/PM） at temperatures of 250—400 °C and strain rates ranging from 0.01 to 1 s^-1. The thermal processing characteristics of the alloy were evaluated using thermal processing diagram analysis. The results showed that the rheological stress of the alloy decreased with the increase of deformation temperature or the decrease of strain rate. Meanwhile， the constitutive equations describing the behavior of rheological stresses were established based on hyperbolic sinusoidal relations， and the thermal deformation mechanism of AZ91 extruded alloy prepared by RS/PM was dislocation creep controlled by lattice diffusion. The dynamic recrystallization and rheological instability behaviors were verified by microstructure， and the alloy has the best machinability when the temperature is above 350 °C and the strain rate is in the range of 0.01—0.1 s^-1.