The results showed that the grainboundary cohesion become weaker and intergranular fracture became dominant with the increasement of superplastic deformation temperature.
结果表明，变形温度愈高，晶界结合强度愈低，沿晶断裂愈明显，晶界滑动愈易实现；
2
The results show that main cause of conchoidal fracture forming is that composition segregation in solidification grainboundary of casting steel reduces the resistance of crack propagation.
结果表明，沿一次晶晶界的成分偏析对裂纹扩展阻力的降低作用是铸钢中贝壳状断口形成的主要原因。
3
The deep and large cavities are formed on fracture surface and grainboundary sliding and intergranular fracture characteristic is obvious on the optimal superplastic deformation condition.