25SiCw/LD2复合材料超塑变形过程中rn位错的分布规律

摘要

采用挤压铸造法制成复合材料并热挤压成板材， 然后对其进行了超塑拉伸实验。 当拉伸温度为570℃， 应变速率为2.0×10-3s-1时获得了280%的延伸率， 用TEM观察了超塑变形过程中位错的变化分布规律。 结果表明， 位错的密度及分布与变形温度及应变速率有一定关系。 在最佳变形条件下， 变形初期位错主要集中在晶界处分布， 随着变形量的加大， 位错向晶粒中间扩展， 并发现有层错及孪晶出现， 这对协调变形具有一定作用。%The 25SiCw/LD2 composites were fabricated using squeeze casting and then hot extruded. Its superplastic behavior was investigated under temperature condition from 55　℃ to 580℃ and strain rate ranging from 8.33×10-4 to 8.33×10-3s-1 in a constant strain rate test. A maximum elongation of 280% was recorded at a strain rate of 2.0×10-3s-1 at 570℃. The roles of dislocations during the superplastic deformation was studied. The result indicates that the dislocation distributes near the boundary of grains at the best draw condition. As the deformation continues, the dislocation expands to the internal of grain. When the elongation is over 100%, stacking faults and twin crystal emerge and play an important part in superplasticity deformation.