Four variants There are 24 different ways to carry out phase transformation. The plane may shift along a 心团应 degrees angles 应体网 The plane may shear along b or c These motions will destroy the 90 angles of the plane The six equivalent planes pass through face diagonals in the cellstructure. Thus, a total of 6x 2x2=24 ariants may grow from the planes. The Structural Cycle of Shape Memory high der low a The cycle starts with the ne austenite When bent, the varia an re-orent from left to ght or vise versa to Et relieve the stress energy. martensite #t austenite O high der low volume high volume Reaction Energy vs Structure Pressure vs Structure essure reaction energy+ H2O(s) 2 H2O less dens more de more dense Nacl(mck salt strurture: NaCl (cesium chloride structur reaction energy t e Tin(s) The transformation of more dense the rock salt to the tetrahedral structur cesium chloride below 13.C) white tin 8 at high P (105 atm).8 The plane may shift along a keeping the 90 degrees angles. The plane may shear along b or c. These motions will destroy the 90o angles of the plane. Four variants The six equivalent planes pass through face diagonals in the CsCl structure. Thus, a total of 6 x 2 x 2 = 24 variants may grow from the planes. There are 24 different ways to carry out phase transformation. The Structural Cycle of Shape Memory The cycle starts with the NiTi in the austenite phase. When bent, the variants can re-orient from left to right or vise versa to relieve the stress. high density low volume low density high volume Reaction Energy vs Structure (gray tin, diamond structure, stable below 13oC) tetrahedral white tin Pressure vs Structure pressure + P - P The transformation of sodium chloride from the rock salt to the cesium chloride structure can be accomplished at 298 K at high P (~105 atm). pressure