GH4738高温合金的应力松弛影响因素

Stress Relaxation Behavior of GH4738 Superalloy

详细研究了紧固件用高温合金GH4738在不同温度和初应力,及不同热处理制度下的应力松弛行为。研究表明:应力松弛的两个阶段之间存在一个槛应力σ'_0,低于此槛应力σ'_0时,塑性应变速率快速下降。随着温度的升高,GH4738合金的松弛稳定性下降,应力松弛速率加快,松弛极限降低。随着初应力的提高,松弛第1阶段松弛速率加快,松弛极限有所增大。不同的固溶温度和稳定化热处理工艺主要影响了合金松弛过程的第2阶段,对其槛应力及松弛稳定性均无明显影响。

The effects of the temperature,the initial stress and various heat treatment regimes on the stress relaxation in the superalloy GH4738 were investigated. The results indicate that a threshold stress is found between two stages. Below the threshold stress,the plastic strain rate falls fast. The relaxation stability of the alloy decreases with the increase of temperature; meanwhile,the stress relaxation rate rises and the relaxation limit declines. The stress relaxation rate of the first stage speeds up and the relaxation limit increases when the initial stress is improved. Different heat treatment systems mainly affect the second stage of the stress relaxation,whereas,no obvious influence is observed on the threshold stress and the relaxation stability.