Autori: L. G. Bujoreanu, S. Stanciu, B. Özkal, R. I. Comãneci, M. Mayer

Editorial: P. ©ittner, L. Heller and V. Paidar, EDP Sciences, ESOMAT 2009 - The 8th European Symposium on Martensitic Transformations, DOI:10.1051/esomat/200905003, p.05003, 2009.

Rezumat:

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 loading-unloading 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 α’-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 thermally-induced reversion, noticeable only during first heating, which was associated with thermally induced reversion of α-stress-induced martensite.

Cuvinte cheie: tensile testing, dilotometry, XRD, SEM, powder metallurgy

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