Martensitic transformation and magnetic properties in Ni–Fe–Ga–Co magnetic shape memory alloys

✍ Scribed by Jian Liu; Nils Scheerbaum; Dietrich Hinz; Oliver Gutfleisch

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 533 KB
• Volume: 56
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2008.03.008

✦ Synopsis

Ni-Fe-Ga-Co is a promising system for magnetic shape memory alloy applications, due to its good ductility, mobile twin boundaries and high transformation temperatures. Unlike previous studies which focused on compositions with a Ga content of 27 at.%, here the martensitic transformation and magnetic properties over a large composition range of Ni 54Àx Fe 20 Ga 26 Co x , Ni 54Àx Fe 19 Ga 27 Co x , Ni 56Àx Fe 17 Ga 27 Co x and Ni 54Àx Fe 18 Ga 28 Co x (x = 0, 2, 4) are investigated. The martensitic transformation temperature T m and the Curie temperature T c can be tailored in a wide range by changing composition and heat treatment. A coupling of martensitic and magnetic transformations at $90 °C is found for Ni 52 Fe 17 Ga 27 Co 4 . Additionally, the effect of thermal cycling on the martensitic transformation of single-and two-phase Ni-Fe-Ga-Co alloys is discussed. Furthermore, an intermediate face-centered cubic phase induced by powderization and transformed into a body-centered cubic phase by aging is reported. The saturation magnetization is significantly decreased by powderization, while recovered by the subsequent aging.