Stability and stabilization of 2H martensite in Cu-Zn-Al single crystals

P. ARNEODO LAROCHETTE; A. M. CONDO; M. AHLERS

PHILOSOPHICAL MAGAZINE

TAYLOR AND FRANCIS

Año: 2005 vol. 85 p. 2491 - 2525

1478-6435

The stabilization of the 2H martensitic phase in Cu-Zn-Al single crystals with an electron concentration e/a = 1.53 was investigated. This orthorhombic 2H martensite was first induced from the cubic b phase by the direct b ®2H or the indirect b ®18R®2H transformations. On loading the 2H martensite, a transition without hysteresis is observed at a stress which was denoted sT1. It was found that this stress is associated with a change in the behaviour of the 2H martensite. A high stabilization of the 2H martensite, around 300 K, is only obtained if an ageing is performed at a stress above sT1. Additionally, the  stresses of the transformation to another martensitic phase, called 18R2, were found to be constant when the value of sT1 is below the retransformation stress. The 2H martensite and its behaviour on ageing were studied by dilatometry, calorimetry, mechanical testing, optical microscopy and transmission electron microscopy (TEM). Models accounting for the stabilization of the 2H martensite on ageing are proposed.