Role of gamma precipitates on the stabilization of martensite in Cu-Zn-Al alloys

In this paper results, obtained via DSG, SEM and TEM techniques, concerning the effect of the thermal cycling and certain distributions of gamma preci pitates and its effect on the martensite stabilization in Cu-Zn-Al single c rystals with e/a = 1.48 and transformation temperatures M-s close at room t emperature are presented. The precipitates were obtained by flash heating i n a molten salt bath to 400 degrees C for times t* = 20 to 100 s and quench ed in water at different temperatures. All the samples were aged in martens itic condition at room temperature for several successive periods (24 h to 1 year). In samples with gamma precipitates and after several aging periods in martensite, the stabilization is reduced (practically eliminated) when compared to the behavior of precipitate-free samples subjected to a step-qu ench type thermal treatment which is known to be effective in reducing the stabilization in copper-based shape memory alloys.