基于马氏体区域化形成的免训练铸造Fe-Mn-Si-Cr-Ni形状记忆合金 Ⅱ.退火对形状记忆效应的影响

来源期刊：金属学报2010年第3期

论文作者：刘刚 彭华备 文玉华 杨坤 孙盼盼

文章页码：288 - 293

关键词：Fe-Mn-Si-Cr-Ni形状记忆合金； 免训练； 铸造； 退火温度； 板条状δ铁素体

Key words：Fe-Mn-Si-Cr-Ni shape memory alloy； training-free； cast； annealing temperature； lathy δ ferrite

摘    要：采用OM和铁素体测量仪研究了铸态Fe-18Mn-5.5Si-9.5Cr-4Ni合金的微观组织随退火温度的改变及其对合金形状记忆效应的影响.结果表明,在773-1173 K之间退火处理能进一步提高合金的形状记忆效应.经973 K退火30 min后,合金的可恢复变形量达到了6.4%,比训练4次的常规Fe-14Mn-5Si-8Cr-4Ni合金高1.2%.当铸态合金在低于1173 K退火30min后,δ铁素体仍为条状,变形时能使应力诱发ε马氏体以区域化的方式形成,合金具有良好的形状记忆效应;当退火温度高于1273 K时,δ铁素体将固溶到奥氏体中,体积分数减少.当退火温度进一步升高到1423 K时,δ铁素体的体积分数显著增加,形态由条状演变为岛状.条状δ铁素体体积分数的减少和岛状δ铁素体的形成导致δ铁素体不能有效分割奥氏体晶粒,合金的形状记忆效应显著下降.

Abstract: The microstructure and memory property evolutions of as-cast Fe-18Mn-5.5Si- 9.5Cr-4Ni alloy with annealing temperature were investigated using OM,ferrite measuring instrument and bending method.The results showed that when the as-cast Fe-18Mn-5.5Si-9.5Cr-4Ni alloy was annealed between 773 and 1173 K,its shape memory effect(SME) was further improved.A high recovery strain of 6.4% was obtained only through annealing the as-cast alloy at 973 K for 30 min,which is 1.2% higher than that of the conventional Fe-14Mn-5Si-8Cr-4Ni alloy after four times thermo-mechanical training.When the as-cast Fe-18Mn-5.5Si-9.5Cr-4Ni alloy was annealed below 1173 K for 30 min,the morphology ofδferrite phase was still lathy and it could make the stress-inducedεmartensite form in a domain manner during deformation,which is the reason why the good SME was obtained in the as-cast alloy annealed below 1173 K for 30 min.When the annealing temperature was above 1273 K,the δ ferrite phase would dissolve in the austenite and its amount decreased. When the annealing temperature was further increased to 1423 K,the amount of δ ferrite phase remarkably increased and its morphology evolved into the island from the lath.The austenite grains could not be well subdivided into smaller domains due to the decrease of lathy δ ferrite phase or the formation of island δ ferrite phase.The SME of this as-cast alloy dramatically decreased when annealed above 1273 K.