碳含量对Fe-15Mn-4.5Si-10Cr-5Ni-C系形状记忆合金性能的影响机制

Effect mechanism of carbon content on properties of Fe-15Mn-4.5Si-10Cr-5Ni-C-based shape memory alloy

为通过调控碳含量获得形状记忆性能优异的铁基形状记忆合金,研究了3种不同碳含量对固溶时效态Fe-15Mn-4.5Si-10Cr-5Ni-C系形状记忆合金微观组织、力学性能及形状记忆效应的影响。结果表明,固溶时效态Fe-15Mn-4.5Si-10Cr-5Ni-(0.05~0.2)C合金的形状记忆效应随碳含量的增加呈现先增后减的趋势。这是由于一方面,随着碳含量的增加,碳原子的间隙固溶强化和第二相碳化物的沉淀析出强化提高奥氏体母相强度,抑制不可逆塑性变形的发生,有利于材料在受力时发生应力诱发奥氏体γ转变为ε马氏体(γ→ε),从而提高形状记忆效应。另一方面,全固溶温度随碳含量的增加而升高。由于全固溶温度的升高,固溶处理后得到的相对粗大的奥氏体晶粒造成奥氏体母相强度的降低。同时,随着碳含量的增加导致ε马氏体相变温度(Mεs)的降低,应力诱发相变过程受到抑制,不利于形状记忆效应。在不同影响机制的相互作用下,碳质量分数为0.091 8%固溶时效态试验合金的形状记忆性能最优。

In order to obtain shape memory alloy with excellent shape memory performance by regulating carbon content,microstructure,mechanical properties and shape memory effect of Fe-15Mn-4.5Si-10Cr-5Ni-C-based alloys with three different carbon contents in solution aging state were studied.The results showed that the shape memory effect of Fe-15Mn-4.5Si-10Cr-5Ni-(0.05~0.2)C alloys increased first and then decreased with the increase of carbon content.It caused by several reasons.One is that the interstitial solution strengthening of carbon atoms and the precipitation strengthening of second phase carbides increase the strength of austenitic matrix with the increase of carbon content,which inhibits the occurrence of irreversible plastic deformation.In other word,strengthening of austenitic matrix facilitates the stress-induced martensitic transformation of the alloys under stress.On the other hand,the complete solution temperature increases with the increase of carbon content.Then,the relatively large austenite grains obtained after solid solution treatment reduced the strength of austenitic matrix.In addition,with the increase of carbon content,the temperature of martensitic phase transformation point(Mεs)decreased,and the strain-induced phase transformation process was inhibited,which was not conducive to the shape memory effect.Under the influence of different mechanisms,the shape memory effect of the experimental alloys in the solution aging state with a carbon mass percent of 0.091 8% was the best.