金刚石-碳化硅超硬复合材料的冲击强度

Dynamic impact strength of diamond-SiC superhard composite

不同于延性介质,脆性介质的失效破坏严重制约着材料的强度.本文采用一种定量描述脆性介质力学性质的格点-弹簧模型,研究了金刚石-碳化硅超硬复合材料的冲击强度及其细观损伤机理,有助于避免灾变破坏、提高冲击强度.在模型中,通过构建不同体积分数比的金刚石和碳化硅两相复合材料,模拟获得了经受冲击波压缩形变后的宏观波剖面,显示出随着金刚石颗粒含量增加,冲击强度逐渐增大,而后减小;对应于这种变化,损伤演化分析揭示出存在三种细观损伤模式,当金刚石颗粒含量在10%—50%范围内增加时,长距离扩展滑移带占主导;当金刚石颗粒含量为70%时,滑移带已由长距离扩展演化为短细滑移带,损伤主要来自于碳化硅基体,多数金刚石颗粒未发生损伤;当金刚石颗粒含量超过70%的临界值后,短细滑移带也将被强烈限制,应力集中致使金刚石颗粒被严重损伤,冲击强度下降.研究结果为优化设计金刚石-碳化硅超硬复合材料以及制备新型抗冲击材料提供了物理认知.

Unlike the ductile materials,the failure seriously limits the strength of the brittle medium.To understand the mechanism of controlling the dynamic impact strength of diamond-SiC superhard composite under shock wave compression,the numerical simulation is conducted with a lattice-spring model that can describe the mechanical properties of diamond-SiC superhard composite quantitatively.For the simulation,the diamond-SiC superhard composite is constructed by different volume content of diamond and SiC particles.The obtainted shock wave profiles indicate that the dynamic impact strength first increases and then decreases with the increase of diamond content in the sample.The analysis based on the meso-scale damage pattern reveals that such a variation of dynamic impact strength corresponds to three damage evolution modes.When the diamond content increases to a value between 10% –50% in volume percentage,the long slip bands are first dominated,and then becomes short slip bands when the diamond content is 70%,and damage happens mainly in SiC matrix whereas most of the diamond particles are not damaged.When the diamond content is above a critical value of 70% in volume percentage,even the short slip bands are limited heavily,which makes it difficult to relax the shear stress on diamond particles and causes serious damage to diamond particles,finally results in the reduction of dynamic strength.