考虑CoCrFeNiAl0.3高熵合金压入尺寸效应的加工硬化指数研究

Study on the work-hardening exponent of CoCrFeNiAl0.3 high entropy alloy considering indentation size effect

采用多种压头对CoCrFeNiAl0.3高熵合金进行微尺度压入测试,研究利用微纳米压入实验获得材料力学性能时,尺寸效应对其测试结果的影响。实验结果表明,压头角度对CoCrFeNiAl0.3高熵合金压入性能具有显著的影响,所测材料硬度值随着压头角度的增大而减小。然后基于两种三棱锥压头的实验结果与压入的自相似过程,得到该材料的加工硬化指数n,发现与材料实际的硬化指数存在着数量级的偏差。为研究产生这一偏差的原因,基于剔除尺寸效应的硬度和压头半锥角的关系得到一个剔除尺寸效应后的加工硬化指数n0。最后,通过第三种三棱锥压头的测试结果对上述两种塑性参数进行了验证,证实在通过微纳米压入实验来获取材料的力学性能时,尺度效应的影响是不可忽略的。

The micro/nano-indentation tests are performed on CoCrFeNiAl0.3 high-entropy alloy(HEA) by multiple indenters to study the indentation size effects(ISEs) on mechanical properties of materials. Experimental results show that the indenter angle has a significant effect on the indentation performance of CoCrFeNiAl0.3 HEA, and the hardness of the tested material decreases as the indenter angle increases. Then, based on the experimental results of two three-sided pyramidal indenters and self-similar process of the indentation, the work-hardening exponent n is obtained. It is found that there is an order of magnitude deviation from the actual work-hardening exponent of materials. In order to study the reason of this deviation, an exponent n0 is obtained based on the relationship between the hardness excluding the ISE and half-angle of a conical indenter. Finally, the two plasticity parameters obtained-above are verified through the test results of the third three-sided pyramidal indenter. It is proved that the influence of ISE cannot be ignored when the mechanical properties of materials are obtained through the micro/nano-indentation tests.