LF6超塑性变形断裂研究

研究了LF6铝合金超塑性变形中的显微组织变化及断口形貌特征。试验结果证明空洞主要在三角界处形核。变形量增加，空洞不断长大，同时有新的空洞产生。晶界滑动是引起空洞长大的主要原因。合金有高的应变速率敏感性，能抑制空洞沿横向晶界的扩展和连接。仅在变形后期，空洞才因试样薄弱处局部应力的增加沿横向晶界大范围扩展连接，并导致合金断裂。变形过程中晶粒的长大和伸长会促使空洞的形核。文中给出了合金超塑性变形断裂的物理模型。

STUDY ON FRACTURE OF SUPERPLASTIC DEFORMATION IN LF6

The microstructural change and fracture morphology during superplastic deformation of LF6 Alumini-um alloy have been examined. The experimental results show that cavities mainly nucleate at triple points and grow continuously with the increase of strain, at the same time, new cavities occllred. Grain boundarysliding is the main cause of cavity growth. Because of high strain rate sensitivity, the alloy can preventcavitise from propagation and interlinkage along transverse grain boundaries. Only at the later stage of de-formation, cavities begin to interlink and propagate extensively along transverse grain boundaries, which isdue to the increase in local stress of the weakpart of the tensile sample, causing the fracture of the alloy.The grain growth and elongation in the tension direction during deformation may promote cavity nucle-ation. A physical model of superplastic de formation fracture of the alloy is presented.