A FUNDAMENTAL STUDY OF THE χ-PHASE PRECIPITATION IN Cu-Al-Ni-Ti-(Mn) SHAPE MEMORY ALLOYS

摘要

χ-phase particles are precipitated when Ti is added as grain refiner to Cu-Al-Ni shape memory alloys. The size distribution of these precipitates is a function of the thermomechanical history of the alloy. The further addition of Mn to improve the alloy properties causes the appearance of a new set of small χ-phase precipitates. The conditions for their appearance are described together with a qualitative model which explains their stability. The presence of Mn is shown to play a central role in controlling the growth of the χ-phase precipitates.