SiC晶须增强铝基复合材料超塑性

SUPERPLASTICITY OF SiC WHISKER ALUMINUM MATRIX COMPOSITE

采用高温拉伸、透射电镜、X射线衍射仪、差示扫描量热计和超塑性经典理论,对低压浸渗、小挤压和热轧制备的SiC晶须增强2024Al基复合材料超塑性的力学行为和变形机制进行了研究。研究表明:复合材料的晶粒细小,尺寸约为1μm;在温度为788K、初始应变速率为3.3×10-3s-1的拉伸条件下,超塑伸长率为370%;DSC曲线上有一小的初期熔化吸热峰,其温度相应于偏晶反应:Al+Al2Cu+Cu4Mg5Si4Alx→液相+Mg2Si,785K;超塑性变形的主导机制为传统的晶界扩散机制和适量液相共同控制的晶界(界面)滑动。

The superplastic mechanical behavior and deformation mechanism of the betaSiC whisker reinforced 2024 aluminum composite, fabricated by lowpressure infiltration and hotrolling after extrusion with a low extrusion ratio of 10∶1, were investigated by using elevated tensile tests, transmission electron microscopy, Xray diffractometer, differential scanning calorimeter and the conventional theory of superplastic deformation mechanism for fine grain metals. The results show that the composite has a fine grain size of about 1 μm, and exhibits a maximum tensile elongation of 370 % in the initial strain rate of 3.3×10-3s-1 at 788 K. A small incipient melting peak on DSC curve of the composite appears and corresponds to the peritectic reaction of Al+CuAl2+Cu4Mg5Si4Alx→Liquid+Mg2Si at 785 K. The superplastic deformation mechanism of the composite is grain boundary (interface) sliding controlled by grain boundary diffusion of the aluminum atom and an appropriate amount of liquid phase.