通过对一种等温锻造GH4169镍基合金进行直接时效处理,蠕变性能测试及组织形貌观察,研究了该合金的组织结构与蠕变行为.结果表明,GH4169合金的组织结构由γ基体,γ′相、γ″相和δ相组成,且各相之间保持共格界面.测定出合金在660℃/700MPa条件下的蠕变寿命为123h.合金在680℃/700MPa的蠕变寿命为39h,在实验温度和应力范围内,计算出直接时效合金的蠕变激活能为588.0kJ/mol.合金在蠕变期间的变形机制是位错滑移和孪晶变形,其中,沿晶界析出的粒状碳化物,可抑制晶界滑移,是使合金具有较好蠕变抗力的主要原因.随蠕变进行,开动的滑移系中位错运动至晶界受阻,并塞积于该区域引起应力集中,当应力集中值大于晶界的结合强度时,可促使其在与应力轴垂直的晶界处发生裂纹的萌生与扩展,直至断裂,是合金在蠕变期间的断裂机制.
By means of direct aging (DA) heat treatment, creep properties measurement and microstructure observation, the microstructure and creep behaviors of the GH4169 superalloy were investigated.Results show that the microstructure of the alloy consists of γ, γ′, γ″ and δ phases, and the coherent interfaces exist between the phases.The creep life of the alloy at 660℃/700 MPa is predicted to be 123h, and 39h at 680℃/700MPa.Under the testing temperature and stress range, the creep activation energy of the alloy is calculated to be 588.0 kJ/mol.The deformation mechanisms of the alloy during creep are dislocation slipping and twin deformation.The granular carbides precipitated along the grain boundaries may restrain the slipping of the boundary, which is thought to be the main reason of the good creep resistance.As the creep goes on, the slipping dislocations activated within the grains are hindered and blocked by the boundaries to cause the stress concentration, which may promote the initiation and propagation of the crack occurring along the boundaries perpendicular to the stress axis, when the value of stress concentration is higher than the bonding strength of the boundaries, up to the occurrence of creep fracture.This is thought to be the fracture mechanism of alloy during creep.
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