화학공학소재연구정보센터
Materials Science Forum, Vol.394-3, 221-224, 2001
Role of oriented stress fields in two-way shape-memory alloys
The common procedures of two-way shape memory effect (TWSNE) training include thermomechanical cycling, pseudoelastic cycling and constrained aging. During thermomechanical cycling or pseudoelastic cycling, dislocations are induced by deformation. For constrained aging, precipitates are induced. These defects are irreversible during forward and reverse transformations, However, oriented internal stresses around these defects were stored. TEM observation showed that the oriented strain fields around precipitates in the austenite attributed their strain fields to martensite variant preference during cooling, During heating to austenite, the stress fields around the precipitates can be recovered again The stress fields of the pair dislocation band were analyzed by molecular dynamics (MD) simulation. The MD simulation indicated that oriented tension stress fields in the middle line of the dislocation band are favorable sites for the martensite nucleation and growth to preference variant. It was found that after training under applied stress, some oriented microstress fields in re-oriented martensite have two-way memory effect during forward and reverse transformation. These oriented stress fields can be termed two-way memory stress fields (TWMSF), The TWMSF contribute their stress fields to the formation of the preferential martensite variants that present TWSME.