黄铜超塑变形时的空洞演变及工艺因素的影响

本文对Ｈ６２黄铜起塑变形时的空洞演变进行了系统而全面的研究，分析了变形温度、应变速率、变形程度和应力状态对空洞生长的影响，发现了不少空洞生长规律，为探索新的抑制空洞长大方法和确定超塑性变形的损伤演变提供了实验资料．

Effect of Process Parameters on Cavity Development of Brass H62 when Superplastically Deformed

The existence of cavities in a metal afrects its mechanical propertics significantly. There exists only very limited amount of experimental evidence in the open literature on development of cavities in metals when superplastically deformed. In this paper, experimcntal findings on such cavity development in brass H62 are believed to be presented for the first time. The findings concerning brass H62 arc: (1)First stage of superplastic deformation. In this stage, superplastic deformation is very small and with increasing deformation, more and more V-shaped cavities are transformed into O-shaped cavities. in this stage, cavity growth is controlled by diffusion. (2) Second stage of superplastic deformation. In this stage, cavities get larger and they coalesce into larger ones, and growth is plastically controlled instead of being controlled by diffusion. (3) In the first stage, area fraction (D and average radius (r) of cavity grow very slowly. In the second stage, fa and r grow very rapidly up till fracture. (4) When stress state is the same, the degree of cavitation near the fracture surface is nearly the same under different temperatures and strain rates. (5) Increase of r follows exponential law.