Early stages of pseudoelastic fatigue in Cu-Zn-Al single crystals cycled in the cryogenic range

J. MALARRÍA, M. SADE , F. LOVEY

ZEITSCHRIFT FUR METALLKUNDE

Hanser

Lugar: Munich; Año: 1996 vol. 87 p. 953 - 962

0044-3093

Cu-Zn-Al single crystals have been pseudoelastically cycled between the bcc austenitic phase (ß) and the 18R martensite, in the cryogenic range. The microstructural changes which take place in the bulk have been studied by different techniques and a consistent description of the defects which are formed is presented. Dislocations and trapped martensite are retained in two-dimensional arrays parallel to the basal plane of the martensite (basal plane defects), and these defects are responsible for the strong temperature effect on the mechanical behavior of the alloys. The dislocations form the bulk defects during the first cycling stage, and afterwords internal stresses are high enough to retain martensite which shows a 2H structure.   Partial recovery takes place at temperatures close to room temperature, which supports the role that  point defects play on the mechanical behavior of these alloys.