【摘要】 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。更多还原

【Abstract】 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(15mm),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 15mm specimen there remains a small amount γ/γ′ eutectic.更多还原