中文摘要：

利用Fe Mn-Si基合金凝固过程中固态转变残留的条状δ铁素体对奥氏体晶粒进行区域化分割,实现应力诱发ε马氏体的区域化形成,提高了合金的形状记忆效应.根据Hammar铬镍当量公式制备了铬镍当量比为1.85的铸态Fe-18Mn-5.5Si-9.5Cr-4Ni合金.利用OM和VSM（振动样品磁强计）研究了合金的室温组织和磁性能.结果表明,在铸态Fe-18Mn-5.5Si-9.5Cr-4Ni合金的室温组织中获得了条状δ铁素体.这些条状δ铁素体将奥氏体晶粒分割成了若干小区域,变形时能约束不同区域应力诱发ε马氏体的扩展.使其以区域化的方式形成.由于应力诱发ε马氏体的区域化形成减少了不同区域马氏体之间的碰撞,在未经任何处理的铸态Fe-18Mn-5.5Si-9.5Cr-4Ni合金中获得了4.9%的可恢复变形量.

英文摘要：

Low cost Fe-Mn-Si based shape memory alloys（SMAs） has not got widely applications because of their poor shape memory effect（SME） and the need of thermo-mechanical training. so developing training-free Fe-Mn-Si based SMAs with high memory property is significant.In the present study,it was put forth that the formation of stress-inducedεmartensite in a domain manner could improve the SME of Fe-Mn-Si based SMAs and it could be realized through subdividing austeniteγgrains into smaller domains using the residual lathyδferrite phase.According to Hammar＇s equivalents,a cast Fe-18Mn-5.5Si-9.5Cr-4Ni alloy with Cr/Ni equivalent ratio of 1.85 was prepared.OM and VSM（vibrating sample magnetometer） examination showed that the as cast microstructure consists ofγaustenite and lathyδferrite phase,and the lathyδferrite subdivided the austenite grains into smaller domains.which makes the stress-inducedεmartensite bands form in a domain manner.Because the collisions between domain-like martensite bands were reduced,a high recovery strain of 4.9%was attained in the as-cast Fe-18Mn-5.5Si-9.5Cr-4Ni alloy.This result provides a novel way of developing training-free Fe-Mn-Si based SMAs.It can be expected that the SME of cast Fe-Mn-Si based SMAs will be further improved through modifying and optimizing alloy compositions, solidification parameters and heat treatment process.