HEATING EFFECTS ON FINE STRUCTURE OF A Cu-Al-Ni-Mn-Ti SHAPE MEMORY ALLOY

摘要

The heating effects on the structure and fine structure of Cu-11.9Al-5Ni-1.6Mn-1Ti (wt%) shape memory alloy have been studied by means of transmission electron microscopy and microscopic compositional analysis. With the increase of the heating temperature and time, the stabilized M18R_1 martensite, transformed from the parent phase of L2_1 structure type, underwent the following structural variations: M18R_1→N18R_1→disorder N9R. Disorder N9R bainite precipitates and retained parent phases were observed in specimens heated at 573 and 623 K for 7.2 ks or longer. When the alloy was heated at 673 K for 133.2 ks, equilibrium α, γ_2 and Ni,Al-rich phases were formed without any retained β_1 parent phase. While the size of the X_s particles decreased in the specimen heated at 623 K for 7.2 ks and they disappeared completely in the specimen heated at 673 K, the X_L particles were coarsened after heating. With the increase of the heating temperature and time the growth of the antiphase domains was observed.