热处理对铸态Zn-5%Al合金的相变超塑性的影响  

Influence of Heat-treatment on Transformation Superplasticity of the as Cast Zn-5%Al Alloy

作　　者：石志强[1] 刘宇慧[1] 李世春[1] 

机构地区：[1]石油大学机电工程学院材料系,东营257061

出　　处：《材料工程》2004年第6期33-36,40,共5页Journal of Materials Engineering

基　　金：国家自然科学基金资助项目 (59871 0 3 1 )

摘　　要：研究表明,铸态Zn-5%Al(质量分数,下同)共晶合金在20～350℃热循环相变条件下进行拉伸时具有超塑性,当施加的初始外应力σ0低于1.4MPa时,铸态Zn-5%Al合金一次热循环过程中的应变增量εt与应力σ0成线性关系,符合Greenwood-Johnson的相变超塑性模型。热循环过程中,铸态Zn-5%Al合金产生的相变内应力变形主要通过α/β界面间的扩散来快速协调。未经淬火处理的铸态Zn-5%Al合金,共晶组织中的α相呈长条状,界面扩散协调效果较差,因而超塑性延伸率较低;而经过淬火处理以后,α相发生球化,其条状长度变短,而且淬火保温时间越长,α相的球化程度越高,在进行热循环相变拉伸时,对内应力塑性变形的扩散协调效果越好,因而更容易获得较大的应变速率和较高的断裂延伸率。Experiment results show that Zn-5%Al (mass fraction,the same below) eutectic alloy as cast reveals superplasticity when it experiences a tensile deformation under a thermal cycling condition (20~350℃). A linear relationship between the plastic strain increment produced after one cycle and the externally applied biasing stress as the stress is less than 1.4MPa, which conforms to the prediction of Greenwood-Johnson model and belongs to the transformation superplasticity. During thermal cycling, internal-stress produces and the plastic deformation is accommodated by α/β interphase diffusion process. After quenching, the eutectic α 　phase in Zn-5%Al alloy is spheroidized, and the longer the holding time, the higher the spheroidization degree. Deffusional accomadation around α phase during thermal cycling is much easier for globular structure than strip, so a fast strain rate in quasi-steady state and a high rupture elongation can be gained.

关 键 词：ZN-AL合金 相变超塑性 热处理 

分 类 号：TG111.7[金属学及工艺—物理冶金]