U-5.7Nb合金绝热剪切带微观组织结构特征

Microstructural Characterization of Adiabatic Shear Band in U-5.7Nb Alloy

摘要:

利用SHPB实验装置对U-5.7Nb合金帽型样品在室温下进行动态加载,获得U-5.7Nb合金绝热剪切带,采用激光共聚焦、SEM、纳米压痕以及TEM等方法开展了U-5.7Nb合金绝热剪切带内组织结构的研究。U-5.7Nb合金绝热剪切带宽约40um,且呈现蚀刻＂暗带＂；剪切带内微裂纹的萌生和扩展导致带内＂破碎＂等轴晶特征组织的出现：剪切带核心区域出现取向高度异性的纳米＂晶畴＂。剪切带内特殊的组织结构变化导致剪切带硬度与弹性模量的不同变化趋势。

Abstract:

The microstructure in adiabatic shear band (ASB) of U-5.7Nb alloy deformed at high strain rate by a split Hopkinson pressure bar (SHPB) was investigated by means of OM, SEM, and TEM. The ASB with black etching color in U-5.7Nb has been observed, and its width was about 40 um. The evolution of microcracks in ASB led to the formation of the micro-feature which like equiaxed "broken grain" with the size of 2-5um in ASB. The nanometre-sized grain domains well below 5 nm are found in the core of ASB, and the orientations of single small grain domain differ completely, even within an area of 1 μm. Microhardness of the ASB is higher than that of the matrix, but elastic modulus of ASB is lower than that of the matrix. The different trends between microhardeness and elastic modulus are caused by the change of microstructure in ASB.