Ti_(3)SiC_(2)陶瓷室温压缩变形行为的尺寸效应

Dimensional effect of room temperature compressive deformation behavior of Ti_(3)SiC_(2) ceramics

通过微柱压缩法研究了Ti_(3)SiC_(2)微柱在室温下的变形行为与其尺寸的关系。结果表明:Ti_(3)SiC_(2)微压缩初期的应力应变曲线为弹性加载,随后曲线斜率逐渐变小直至断裂,屈服强度和杨氏模量随试样尺寸的减小而增大。利用扫描电镜及透射电镜对微柱的变形机制进行了研究,发现基底滑移是Ti_(3)SiC_(2)微柱室温下唯一的滑移体系,基面位错滑移到自由表面最终形成边缘位错墙。结合位错匮乏机制和单臂位错源模型,关于Ti_(3)SiC_(2)微柱微压缩的尺寸效应可以解释为由于在小尺度范围内位错的密度很小,使得位错形核困难,因此需要更高的应力来激活新的位错源;但随着微柱尺寸增大,留在试样内部的位错通过相互反应生成位错源,此时位错运动应力成为变形行为的主导机制。

Relationship between the deformation behavior of Ti_(3)SiC_(2)micropillar and its size at room temperature was studied by micropillar compression method.The results show that the stress-strain curves of the Ti_(3)SiC_(2)micropillar at the initial stage of micro compression is elastic loading,and then the slope of the curve gradually decreases until fracture,and the yield strength and Young􀆳s modulus increase with the decrease of sample size.The deformation mechanism of the micropillar was studied by scanning electron microscopy and transmission electron microscopy.It is found that the basal slip is the only slip system of the Ti_(3)SiC_(2)micropillar at room temperature,and the basal dislocations slip to the free surface and finally form an edge dislocation wall.Combined with the dislocation deficiency mechanism and the single arm dislocation source model,the size effect of micro compression of the Ti_(3)SiC_(2)micropillar can be explained as that the dislocation nucleation is difficult due to the small dislocation density in a small scale,so higher stress is needed to activate a new dislocation source.However,with the increase of micropillar size,the dislocations remaining in the sample react with each other to form dislocation sources,at this time,the dislocation motion stress becomes the dominant mechanism of deformation behavior.