定向凝固NiAl-25Cr多相合金的超塑性研究

Investigation on Superplasticity for DS Multiphase NiAl-25Cr Alloy

研究了定向凝固NiAl-25Cr合金的超塑性行为。通过OM、SEM和TEM观察合金超塑性组织和测试力学性能，结果表明：定向凝固Ni-25Al-25Cr合金由β—NiAl枝晶干、β-Cr枝晶间、枝晶干内的细小β～Cr颗粒以及枝晶间的β-NiAl＋α-Cr共晶组成；合金超塑性变形的屈服应力和流变应力随着应变速率的增大和温度的降低而增大；在温度为850～1100℃，应变速率为1．67×10^-4～1．67×10^-2s^-1内，拉伸延伸率在80％～160％之间；合金超塑性变形后，枝晶干沿拉伸轴方向伸长，而且枝晶干被新的小晶粒分割；合金超塑性变形来自于加工硬化（位错滑移）和应变软化（动态回复和动态再结晶）的平衡。

The superplastic behavior forDS Ni -25Al-25Cr was investigated herein. The microstructure was obtained by OM, SEM and TEM, and the mechanical properties were measured. The results reveal that the DS Ni-25Al-25Cr alloy consists of β-NiAl dendritic arms,α-Cr interden- dritic region,fine α-Cr particles in dendritic arms and the β-NiAl ＋α-Cr euteetie in the interdendritic region. The yield strength and the flow stress increase with increasing strain rates and decreasing temperature during superplastic deformation. The tensile elongation falls into the ranges of 80～160% at the corresponding temperature range 850～1100℃ and strain rate range 1.67× 10^-4s^-1～1. 67× 10^-2s^-1. The balance between work hardening （by dislocation glide） and work softening （by dynamic recovery and recrystallization） is responsible for the superplastic deformation behavior of the alloy.