A non-invariant plane model for the interface in CuAlNi single crystal shape memory alloys

A non-invariant plane model for the austenite-martensitic (A-M) interface i n CuAlNi single crystal shape memory alloys (SMAs) is proposed in this pape r. The model is based on the crystallography of martensitic transformation and the recent uniaxial tensile Moire tests on Cu-14%Al-4.12%Ni (wt%) singl e crystals, The two types of specimens used have the same tensile axis orie ntation but have different transition temperatures. One exhibits Shape Memo ry Effect (SME) and the other exhibits Superelasticity (SE). In the case of SME, the plane invariant nature of the A-M interface is well verified by t he Moire test. On the contrary, the A-M interface in the case of SE was ide ntified to be a non-invariant plane. A crystallography-based model is propo sed to explain the formation of this non-plane-invariant A-M interface in S E and is used to predict the resultant interface structure and the transfor mation strain of the stress-induced beta(1)-->beta'(1) transformation in Cu AlNi. The comparison between the theoretical calculations and the experimen tal results support the proposed model. (C) 2000 Elsevier Science Ltd. All rights reserved.