Ti_3SiC_2陶瓷的能量耗散机理

The energy-dissipation mechanism of Ti_3SiC_2 ceramic investigated by indentation

采用维氏和赫兹压痕法研究了Ti3SiC2接触损伤及其演变.结果表明,在维氏压痕接触损伤区从表面到纵深的不同损伤排序为:表面的晶粒粉碎,亚表面的晶粒分层或破碎,再远处的晶粒完好;在赫兹压痕接触损伤区剪切损伤带以内的晶粒破碎,剪切带以外的晶粒完好.因此,造成压痕处的局部能量耗散,使应力传递受限、应力集中下降,使这种三元层状陶瓷具有准塑性特征.用声发射(AcousticEmission,简称AE)系统监测赫兹压痕加卸载过程中的局部损伤过程,发现在加载过程中声发射信号密集,卸载过程声发射信号稀疏,证明了损伤和局部能量耗散的不可逆性.Ti3SiC2陶瓷的能量局部耗散机理是弱晶界面开裂和晶粒分层导致的局部软化和破碎,在损伤区范围内吸收能量并使局部应力释放.

Contact damage of Ti3SiC2 under Vickers and Hertzian indentations was investigated to understand the energy-dissipation mechanism during the indentation loading. Dissimilar damage modes were revealed at different depths beneath the indent. SEM examinations on the fracture section revealed that under Vickers indentation, grains in the surface layer were crushed into powders, while those in the subsurface layer delaminated, slipped and crushed into fragments, and the grains far from the indent did not deform. Under Hertzian indentation the grains in the damaged zone induced by shear stress slipped, delaminated and fragmentized, while those outside the shear zone did not deform. The damage in the contact region dissipated the energy so that Ti3SiC2 possessed quasi-plasticity. Acoustic emission（AE） counts monitoring of the loading and unloading processes of Hertzian indentation were irreversible in the loading process. Such local energy-dissipation and damage mechanism originated from the nanolayered structure and weak grain boundaries of Ti3SiC2.