基于小冲孔试验的工业纯钛塑性强化与损伤效应研究

Study on plastic strengthening and damage effects of commercial pure titanium based on small punching test

为了探究塑性变形对TA2的塑性强化与损伤效应,开展了不同塑性变形量下TA2的小冲孔试验。结果表明,在15%塑性变形量以内,小冲孔试验强度参量表明塑性变形对TA2起到了强化效应,屈服强度和抗拉强度均提高,强化率分别为12.8%和10.9%,屈强比基本保持不变;当塑性变形量达到15%,屈服强度增幅减小,而抗拉强度有所下降,致使屈强比不断增大直到趋近于1。因此在小的塑性变形范围内,有利于TA2的塑性应变强化,但当塑性变形量超过15%后,塑性变形产生的强化效应不再显著,而塑性损伤趋于明显,导致材料的韧性下降。最后,基于微观组织分析可以发现,在15%塑性变形量以内,强化的原因是孪晶组织作用;塑性变形量超过15%时,塑性损伤的原因一方面是在塑性强化过程中消耗了晶粒的部分可变形量,另一方面是在晶界处产生了大量滑移带的堆积,造成了材料韧性的下降。

To explore the plastic strengthening and damage effects of plastic deformation on TA2,small punching tests of TA2 with different plastic deformations were carried out.The results show that within the plastic deformation of 15%,the strength parameters of small punching tests indicate that plastic deformation has strengthening effect on TA2,and the yield strength and tensile strength are improved.The strengthening rates are 12.8%and 10.9%,respectively,and the yield ratio remains basically unchanged.When the plastic deformation reaches 15%,the increase amplitude of yield strength decreases,while the tensile strength slightly decreases,resulting in the constant increase of yield ratio until 1.Therefore,within small plastic deformation range,it is beneficial for the plastic strain strengthening of TA2,but when the plastic deformation exceeds 15%,the strengthening effect of plastic deformation is no longer significant,and the plastic damage tends to be obvious,resulting in the decrease of the toughness of material.Finally,based on the microstructure analysis,it can be found that within the plastic deformation of 15%,the reasons for the strengthening is the action of twin structure.When the plastic deformation exceeds 15%,the reasons for plastic damage are:on the one hand,some of the deformable of grains is consumed during plastic strengthening,and on the other hand,a large number of slip bands accumulate at the grain boundary,resulting in the decrease of the toughness of material.