应力应变状态对FeMnSi系形状记忆合金形状记忆效应的影响

借助分析计算弯曲变形下试样内部的主应力分布研究了Fe - 17Mn - 10Cr- 5Si- 4Ni合金在弯曲变形下的形变恢复特性。结果表明 ,在弯曲变形下 ,试样处于复杂的三向主应力作用状态。在小于 2 %低的弯曲变形量下 ,三向主应力中切向主应力σθ 从数值上占据主要 ,因而试样的变形主要来自于σθ 的作用结果。此时 ,变形试样内外层间存在的切向应力值差Δσθ 导致彼此间形变恢复过程的相互约束 ,从而使合金的形变恢复率不能达 10 0 %。随着弯曲变形量的增大 ,合金的变形逐渐置于三向主应力的综合作用之下 ,ε马氏体将被多取向地诱发形成且αM′的形成量越来越大 ,因而合金的形状记忆效应快速下降

Influenece of stress-strain state on shape memory effect of FeMnSi-based alloy

The deformation recovery characteristics of Fe-17Mn-10Cr-5Si-4Ni alloy under bending have been studied by analysing the principal stress distribution. The results show that the bending deformation results in the specimen to be in the triaxial principal stress condition . At low bending strain (less than 2%), the tangential principal stress σ θ is the major stress which leads to the deformation. Consequently, Δσ θ existing between the inner layer and the outer layer of the specimen leads to the deformation recovery processes of the different positions in the specimen to restrain each other, therefore the deformation recovery ratio of the alloy is less than 100%. With the increase in bending strain, the deformation of the alloy is dependent on the overall action of the triaxial principal stresses,ε martensite structures are induced to form in multiple orientations ,and the amount of α′ martensite structures is more and more,which lead to the shape memory effect of the alloy to weaken rapidly.