Microstructure changes in two phase β+γ Co-Ni-Al ferromagnetic shape memory alloys in relation to Al/Co ratio

Wojciech Maziarz 1Jan M. Dutkiewicz 1Ruben Santamarta 2Eduard Cesari 2

1. Polish Academy of Sciences, Institute of Metallurgy and Materials Sciences (IMIM PAN), Reymonta 25, Kraków 30-059, Poland
2. Dept. de Física, Universitat de les Illes Balears (UIB), Palma de Mallorca E-07122, Spain

Abstract

The microstructure of annealed at 1200°C and water quenched Co35+x-Ni40-x-Al25 (x = 0, 2.5, 5.0) ferromagnetic shape memory alloys has been investigated by optical (OM) and analytical transmission electron microscopy (TEM). The deformed microstructure consisted of elongated grains of martensite and γ phases as observed using polarized OM and Nomarski contrast. The annealing twins were found frequently in the γ phase. The volume fraction of γ phase has been determined using quantitative image analysis method. TEM observations raveled frequent stacking faults within martensite and its teragonality as well as dissociated dislocations within γ phase. The crystallographic relationship between martensite and γ grains has been determined basing on electron diffraction patterns. The elemental mapping technique and chemical point analyses allowed to determine the composition of particulate phases. The measured Al/Co ratio in the β phase of quenched alloys has been shown to be related to Ms temperature.

 

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium E, by Wojciech Maziarz
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 14:33
Revised:   2009-06-07 00:44