对电沉积SiC/Ni复合材料进行了低温超塑性拉伸实验,结果发现:平均晶粒尺寸为200nm的SiC/Ni复合材料在温度430℃初始应变速率为8.33×10-4s-1的变形条件下,获得最大延伸率571.2%,应变速率敏感指数为0.32。利用扫描电镜对断口形貌及变形后试样的组织进行的观察表明:断裂模式主要是沿晶断裂;晶粒有不同程度的长大,晶粒的长大速率的不同形成了变形后大小晶粒的混合组织,且沿拉伸方向拉长。应力-应变关系曲线表明:应力随着应变的增大而增大,增加到峰值后开始减小,材料进入准稳定变形阶段,实现大变形。SiC的加入增加了基体组织的稳定性,有利于材料超塑性的实现。超塑变形机理为晶界滑移和位错滑移塑性。
Abstract
Low temperature superplastic tensile tests were carried out in electrodeposited SiC/Ni composite with an average grain size of 200 nm.The results showed that the maximum elongation of 571.2% was obtained at temperature of 430℃ and strain rate of 8.33×10-4s-1,where the strain rate sensitivity was 0.32.Observation of fracture surfaces and the deformed microstructure showed that the fracture mode of the material was intercrystalline fracture,and grain grew to different extent and elongated along the tensile axis.Different grain growth rates resulted in final structure made of large and small grains.Stress-strain curves indicated that stress increased to peak values then decreased.Large deformation realized in the quasi-steady flow stage after peak stress.The addition of SiC has a positive effect on the thermal stability of matrix structure,thus has a favorable effect on the superplasticity.The deformation mechanisms were grain boundary sliding and dislocation plasticity.
关键词
超塑性 /
电沉积 /
断口 /
复合材料
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Key words
superplasticity /
electrodeposition /
fracture /
composite
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脚注
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基金
国家自然科学基金资助项目(50575049)
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