定向凝固中热裂纹的形成过程

Formation of Hot Tearing in Directional Solidification

摘要:

通过定向凝固Ａｌ－Ｃｕ合金和Ｒｅｎｅ１２５合金热裂纹的电子扫描显微分析，发现了热裂纹中晶间搭桥的存在，以及裂纹断面晶间搭桥破断留下的痕迹。并根据合金凝固过程的理论分析，对热裂纹的形成过程进行了合理的推测。

关键词:合金 凝固过程 热裂纹 电子扫描显微镜

Abstract:

Based on solidification analysis in which mechanical properties of quasi-solid alloy and compensation of liquid alloy in dendritic boundries are considered, solidification process of alloy is divided to four stages, which are quasi-liquid stage, compensated stage, uncompensated stage and dendritic bridging stage Hot tearing happened in uncompensated stage In order to investigate hot tearing process, SEMA was carried out for hot cracks in directionally solidified Al-Cu and Renel25 alloys Dendritic bridges were discovered in those cracks And tracks caused by dendritic bridges broken were also discovered in crack sections Therefore, hot tearing is proved to be caused by dendritic bridge breaking and developed through cavities between bridges joining together

Key words:hot tearing, solidification analysis, SEMA, dendritic bridging,