微观组织对GH4720Li合金力学性能的影响

对GH4720Li合金锻制棒坯进行热处理前后的微观组织观察,对一次γ'相进行能谱分析,并对其进行20,650℃拉伸力学性能检测.结果表明,合金中一次γ'相的数量由棒坯边缘向中心逐渐减少,但其尺寸逐渐增大;热处理对一次γ'相的数量和分布的影响不显著,但对二次γ'相的影响十分显著;合金强度由棒坯边缘向中心先升高再降低,其塑性则是逐渐升高,一次γ'相的数量和塑性是影响合金塑性的主要因素;一次γ'相与基体的相界是拉伸断裂的主要裂纹源;随着析出温度升高,一次γ'相的塑性增加,其Al,Ti元素含量下降,而Cr,Co,Mo和W元素含量升高.

Influence of Microstructure on Mechanical Property of GH4720Li Alloy

The microstructures of GH4720Li alloy samples which were cut from GH4720Li alloy bar including forging and heat treatment states were observed， and the phase compositions of primary γ′ was measured via energy spectrum analysis. The tensile properties of the samples through heat treatment were tested at 20 and 650℃. The results indicated that the quantity of primary γ′ of GH4720Li alloy decreases from the edge to the center of the bar while the size of primary γ′ increases gradually. The influence of heat treatment on the quantity and distribution of primary γ′ is not noticeable， but the influence of heat treatment on the quantity and distribution of secondary γ′ is noticeable. The tensile strength of GH4720Li alloy increases at the first and decreases in the end from the edge to the center of the bar， but the plasticity of alloy increases gradually. The quantity and plasticity of primary γ′ are the chief factors influencing the alloy plasticity. The phase boundary of primary γ′-γ is the crack source in the tensile tests. As the precipitation temperature rises， the plasticity of primary γ′ increase， the element contents of aluminum and titanium in the primary γ′ decrease， but the element contents of chromium， cobalt， molybdenum and tungsten in the primary γ′ increase.