ESOMAT 2009, 05003 (2009)
DOI: 10.1051/esomat/200905003

Comparative study of the structures of Fe-Mn-Si-Cr-Ni shape memory alloys obtained by classical and by powder metallurgy, respectively

L. G. Bujoreanu¹, S. Stanciu¹, B. Özkal², R. I. Comăneci¹ and M. Meyer<sup>3

1</sup>  Faculty of Materials Science and Engineering, The "Gh. Asachi" Technical University from Iaşi, Bd. D. Mangeron 61A, 700050 Iaşi. Romania
²  Particulate Materials Laboratory, Metallurgical and Materials Engineering Department, Istanbul Technical University, 34469 Maslak – Istanbul, Turkey
³  NETZSCH Gerätebau GmbH, Wittelsbacherstrasse 42, Selb/ Bavaria, 95100, Germany

lgbujor@tuiasi.ro

Published online: 1 September 2009

Abstract
Hot rolled specimens of low-manganese Fe-Mn-Si-Cr-Ni shape memory alloys, produced by classical and by powder metallurgy (CM and PM) with mechanical alloying, respectively, were analysed by tensile loadingunloading tests (TENS), by dilatometry (DIL), by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Solution annealed specimens had two-phase structure, comprising γ-austenite and thermally induced α-martensite. The formation of γ’-stress-induced martensite during TENS was ascertained by SEM and XRD being accompanied by rounded loading portions on stress-strain curves, characteristic to transformation induced plasticity, which preceded long stress plateaus with low tilt. Even if loading behaviour changed from transformation induced plasticity, on first loading, to slip induced plasticity, during subsequent ones, the specimens maintained their pseudoelastic behaviour on each unloading. DIL responses of the elongated CM and PM specimens emphasised a thermallyinduced reversion, noticeable only during first heating, which was associated with thermally induced reversion of γstress-induced martensite.

© Owned by the authors, published by EDP Sciences 2009