Zn-0.66％Cu-0.38％Mn合金的超塑性

Superplasticity of Zn-0.66％ Cu-0.38％ Mn Alloy

本文对一种在固溶体基体上分布有弥散化合物微粒的锌基合金进行了超塑性研究。急冷凝固的Zn-0.66％Cu-0.38％Mn合金经晶粒微细化处理后获得了晶粒平均直径小于10μm的微细晶粒组织。在250～300℃和3×10^(-4)～4×10^(-3)s^(-1)的初始应变速率拉伸条件下,此合金呈现出典型的超塑变彤力学特征。Ⅱ区内的m值约为0.49,延伸率约为300％。250℃时应变速率、流变应力σ及平均晶粒直径d之间符合ocσ~2/d^2关系。在250～300℃温度范围和恒定应力条件下测得此合金的超塑变形激活能为54.2±5.6kJ/mol,与纯锌的晶界自扩散激活能很接近,说明此合金的超塑变形是由晶界自扩散所控制的。

n this paper, the superplasticity of a zinc base alloy containing fine dispersoid particles of intermetallic compounds has been investigated. After a special thermomechanical treatment, the chill cast slab of a Zn-0.66%Cu0.38% Mn alloy was converted into fine-grained sheets in which the average grain diameter was <10 μm. In the temperature range from 250℃ to 300℃ with the initial strain rates from 4×10^(-3)s^(-1) to 3×10^(-4)s^(-1), this alloy exhibits typical superplastic mechanical behavior. The m value and the fracture elongation in region Ⅱ are about 0.49 and 300% respectively. At 250℃, a relation of ∞σ~2/d^2 was observed. The activation energy for superplastic flow of this alloy measured under constant stress condition in the temperature range of 250℃～300℃ is 54.2+5.6kJ/mol which is comparable to the activation energy for grain boundary diffusion in pure zinc. This demonstrates that the strain rate of superplastic flow of the alloy is controlled by the grain boundary self-diffusion.