25SiC_W／LD2复合材料超塑变形过程中的组织形态及其变化

CHANGE OF MICROSTRUCTURE DURING SUPERPLASTIC DEFORMATION IN 25SiC_W/ LD2 COMPOSITES

采用挤压铸造法制成复合材料并进行了热挤压，对上述材料进行了超塑拉伸实验．当拉伸温度为５７０℃，应变速率为２．０５×１０^（－３）ｓ^（－１）时得到２８０％的延伸率．用ＴＥＭ观察了超塑变形过程的组织结构．结果表明，在变形过程中晶粒始终保持等轴状，位错的形态随变形量的增大不断变化，逐渐形成缠结及胞状结构，当变形量超过５０％时出现层错与孪晶，它们对超塑变形起一定的作用．

The 25SiCw/LD2 composites is fabricated using squeeze casting method and then hot extruded.The superplastic behavior of it was investigated under temperature condition from 500t to 580℃and strain-rates ranging from 8.33 ×10￣(-4)to 8.33×10￣(-3)s￣(-1)in a constant strain rate test.A maximum elongation of 280% was recorded at a strain rate of 2 ×10￣3s￣(-1) at 570℃.The role of dislocations during the superplastic deformation was studied.Stacking faults and twin crystal in the matrix emerged and played positive role to the superplastic deformation after the elongation over 50%.