高温低周疲劳损伤对FGH96合金力学性能影响的实验研究

Experimental Study on the Effects of High Temperature Low-cycle Fatigue Damage on Mechanical Properties of FGH96 Alloy

摘要:

通过设计FGH96粉末高温合金的高温低周疲劳试验、高温单轴拉伸试验，研究了不同应力水平下高温低周疲劳损伤对合金力学性能的影响，结合对断口形貌的观察，分析了合金力学性能改变的微观机理。结果表明，受位错运动的影响，合金的屈服强度、抗拉强度在损伤前期表现出上升的趋势；损伤后期，随着材料内部裂纹的不断增多及扩展，合金的弹性模量、抗拉强度不断退化。合金力学性能的变化与应力水平表现出明显的相关性。显微断口分析表明，随着损伤程度的增加，合金高温拉伸断裂模式由韧性逐渐向脆性转变，高温氧化加速了断裂模式的转变。

Abstract:

High temperature low-cycle fatigue tests and high temperature tensile tests were designed to study the effects of high temperature low-cycle fatigue damage on mechanical properties of FGH96 powder metallurgy superalloy. The microscopic mechanism of the change of the mechanical properties of FGH96 alloy was analyzed by observing the fractographs. Results show that the yield stress and tensile strength of FGH96 alloy show an upward trend in the early stage of damage due to the effects of dislocation motion; in the later stage of damage, the elasticity modulus and tensile strength of FGH96 alloy are continuously degraded as the internal cracks increase and expand. The change of the mechanical properties of FGH96 alloy shows a clear correlation with the stress level. The microfracture analysis shows that with the increase of the damage degree, the high temperature tensile fracture mode gradually changs from ductile to brittle, and is accelerated by high temperature oxidation.