GH4738高温合金的应力松弛行为

The stress relaxation behavior of GH4738 superalloy

摘要:

高温合金的松弛性能研究对于使用该合金制造的紧固件在服役过程中的工作条件选择以及松弛规律提供实验依据。本文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 ,低于此槛应力 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,松弛第一阶段松弛速率加快,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二阶段,对其槛应力及松弛稳定性均无明显影响。

Abstract:

The research of the stress relaxation behavior in superalloys provides the reference of selecting the appropriate working conditions for fasteners and experimental basis for relaxation laws . The effects of the temperature,the initial stress and various heat treatment regime on the stress relaxation in the superalloy GH4738 were investigated. The results indicated that: a threshold stress was found between two stages. Below the threshold stress, the plastic strain rate fell fast. The relaxation stability of the alloy decreased with the increase of temperature, meanwhile, the stress relaxation rate rised and the relaxation limit declined. The stress relaxation rate of the first stage speeded up and the relaxation limit increased when the initial stress was improved. Different heat treatment systems mainly affected the second stage of the stress relaxtion, whereas, no obvious influence was observed on the threshold stress and the relaxation stability.