粉末热等静压和铸造Be-Al合金的室温拉伸断裂机理

Fracture mechanisms of hot isostatic pressed powder and as-cast Be-Al alloys under tensile tests at room temperature

研究了粉末热等静压和精密铸造成型的Be-Al合金室温拉伸断裂模式。结果表明:粉末热等静压Be-Al合金的断口上有一个主裂纹源和多个次裂纹源,裂纹起源于Be/Al相界面和Al相的细薄组织,裂纹扩展与汇合同样沿此途径进行,断裂是各个裂纹源不断汇合韧脆反复的过程,属于相间断裂,说明热等静压Be-Al合金的界面结合强度小于Be相强度;铸态Be-Al合金的断口由Be相解理和Al相延性断裂组成,断裂机理是Be相先解理断裂后,再发生Al相急剧塑性变形,最后Al相断裂,裂纹成形于Be相内部终止于Al相,属脆性准解理断裂,说明铸态Be-Al合金界面结合强度大于Be相强度。

The tensile fracture behaviors of hot isostatic pressed（HIPed） powder and as-cast Be-Al alloys were studied systematically by using scanning electron microscope（SEM） and electron probe of microanalysis（EPMA）.The results show that one main crack source and many sub-crack sources happen in the fracture microstructure of the HIPed powder Be-Al alloy.The crack sources are derived from the Be/Al phase interfaces and the thin area of the Al phase,which is followed by crack extending and converging.The fracture is one course of many alternate sub-processings of various crack sources extending-converging mainly along the Be/Al interfaces,indicating that the interface bonding strength is smaller than that of the Be phase.In contrast,the fracture microstructure of the as-cast Be-Al alloy is composed of cloven Be phase and ductilely fractured Al phase.Its fracture mechanism is through the cleavage cracking of the Be phase first,and then Al phase cracking by its severe plasticity deformation.The crack generates in the Be phase and ends in the Al phase,which belongs to the brittle sub-cleavage fracture,indicating that the interface bonding strength is larger than that of the Be phase in the as-cast Be-Al alloy.