Martensite-austenite stability shifts due to the presence of {gamma}-phase precipitates in Cu-Zn-Al alloys

Journal Article · Fri May 21 04:00:00 EDT 1999 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(99)00075-5· OSTI ID:20023096

Roqueta, D O; Lovey, F C; Sade, M

The presence of two-phase microstructures has been shown to affect many characteristics of the martensitic transformation. A study of the hysteresis behavior in {beta}-Cu-Zn-Al alloys containing a fine distribution of {gamma}-type precipitates has already been presented: an almost linear dependence on the mean precipitate volume of the asymptotic hysteresis width (that is, the one obtained after {approximately} 200 cycles, when its value no longer evolves) has been explained with the aid of a simple model of gliding mechanisms around each precipitate, while three different regimes for the initial evolution with cycling have been related with different kinds of defects created on transformation for each range of mean precipitate sizes. In particular, for precipitates larger than {approximately}32 nm average size, the high hysteresis drop in the first cycles can be related to the appearance around the precipitates of microplates of a variant opposite to the induced one. Regarding the relative stability between martensite and the {beta} phase, the following facts have been depicted: after {approximately} 200 cycles the hysteresis loop has an almost stable shape with a certain hardening that, in principle, makes it nontrivial to define an equilibrium stress. In the present work the authors show a correlation between the hardening of the cycle and the dispersion of precipitate volumes, and two different behaviors of the equilibrium stress depending on whether it is measured at the beginning of the cycle or at the situation of 50% of the sample transformed. An interpretation of these results is given which permits an estimate of interface energy of the microplates.

• Research Organization: Comision Nacional de Energia Atomica, Bariloche (AR); Univ. Nacional de Cuyo, Bariloche (AR)
• OSTI ID: 20023096
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 12 Vol. 40; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
AUSTENITE
COPPER ALLOYS
CORRELATIONS
CRYSTAL-PHASE TRANSFORMATIONS
HYSTERESIS
MARTENSITE
PRECIPITATION
ZINC ALLOYS