The atomic configurations at macro-twin interfaces between micro-twinned martensite plates in Ni65Al35 material were investigated using transmission electron microscopy. The observed structures were considered with regard to their possible formation mechanisms. A distinction was made between cases where the micro-twins, originating from mutually perpendicular {110} austenite planes, enclosed a final angle greater or smaller than 90°. Two different configurations, a crossing- and a step-type were described. Depending upon the case, tapering, bending and tip-splitting of the smaller micro-twin variants were observed. The most reproducible deformations occurred within some 5 to 10nm of the interface while various structural defects were observed further from the interface. The structures and deformations were interpreted in terms of the coalescence of 2 separately nucleated micro-twinned martensite plates and the accommodation of stresses.

Nano-Structures at Martensite Macrotwin Interfaces in Ni65Al35. Boullay, P., Schryvers, D., Ball, J.M.: Acta Materialia, 2003, 51[5], 1421-36