一种镍基单晶高温合金凝固组织的截面尺寸效应

Effects of Section Sizes on Microstructure of a Nickel-base Single Crystal Superalloy

采用快速凝固法拉制壁厚分别为0.8,1.5,2.5mm的单晶薄壁试样,研究了一种镍基单晶高温合金凝固组织的截面尺寸效应。结果表明:随截面尺寸减小,不同厚度薄壁试样凝固组织一次枝晶间距减小,二次枝晶间距先增大后减小;相对于15mm试样,薄壁试样枝晶干处γ′相尺寸变小,枝晶间γ′相尺寸变化不大,γ/γ′共晶含量明显减少。能谱分析表明不同厚度薄板试样元素偏析程度相对于15mm试样均得到一定缓解,但各不同厚度试样元素偏析变化不大。对三种厚度薄板试样进行真空固溶热处理后发现共晶已基本消除,而15mm试样还残留少量共晶。

Effects of section sizes on microstructure of a nickel-base single crystal superalloy have been studied by making directly thin-wall specimens whose wall thicknesses are 0.8,1.5mm and 2.5mm by using the Bridgmen procedure. The results show that, with the decrease of section size, the primary dendritic arm spacing of thin-wall specimen decreases, and the secondary dendritic arm spacing increases firstly and then decreases; comparing with the standard specimen（φ15mm）, the size of γ′ phase particles in the dendritic core decreases but that of interdendritic changes slightly, the volume fraction of γ/γ′ eutectic also decreases obviously. EDS analysis shows that microsegregation of thin-wall specimens has been suppressed comparing with the standard specimen, but the microsegregation of specimens with different thickness isn＇t obvious. Furthermore, γ/γ′ eutectic of thin-wall specimens was ruled out basically after vacuum solid-solution treatment, but for φ15mm specimen there remains a small amount γ/γ′ eutectic.