Ll. Escoda

Thermal and magnetic field-induced martensite-austenite transition in Ni50.3Mn35.3Sn14.4 ribbons

Thermal and field-induced martensite-austenite transition was studied in melt spun Ni50.3Mn35.3Sn14.4 ribbons. Its distinct highly ordered columnarlike microstructure normal to ribbon plane allows the direct observation of critical fields at which field-induced and highly hysteretic reverse transformation starts (H=17kOe at 240K), and easy magnetization direction for austenite and martensite phases with respect to the rolling direction. Single phase L21 bcc austenite with TC of 313K transforms into a 7M orthorhombic martensite with thermal hysteresis of 21K and transformation temperatures of MS=226K, Mf=218K, AS=237K, and Af=244K.

Martensitic transformation in Ni50.4Mn34.9In14.7 melt spun ribbons

Single phase microcrystalline ribbon flakes with the average elemental composition Ni50.4Mn34.9In14.7 were produced by rapid quenching using melt spinning technique. Fracture cross section micrographs of ribbons show the formation of a columnar-like microstructure, with the longer axis of grains aligned perpendicular to ribbon plane. X-ray diffraction and thermomagnetic analysis show that samples are single phase with L21-type austenite as high-temperature parent phase (Curie point of 284u2009K). At low temperatures austenite transforms into a ten-layered structurally modulated monoclinic martensite. The characteristic phase transition temperatures and thermal hysteresis of the reversible martensite–austenite transformation were MS = 262u2009K, Mf = 245u2009K, AS = 262u2009K, Af = 270u2009K and ΔT = 10u2009K. The crystalline directions [2u20092u20090] of austenite and [1u20092u20095] of martensite were found preferentially oriented normal to the ribbon plane. The measurement of magnetization isotherms up to 80u2009kOe confirmed the occurrence of the field-induced reverse martensitic transformation.

Microstructure and magnetic properties of Ni50Mn37Sn13 Heusler alloy ribbons

The Heusler alloy Ni50Mn37Sn13 was successfully produced as ribbon flakes of thickness around 7–10μm melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be MS=218K, Mf=207K, AS=224K, and Af=232K; the thermal hysteresis of the transformation is 15K. Ferromagnetic L21 bcc austenite phase shows a Curie point of 313K, with cell parameter a=0.5971(5)nm at 298K, transforming into a modulated 7M orthorhombic martensite with a=0.6121(7)nm, b=0.6058(8)nm, and c=0.5660(2)nm, at 150K.

Microstructure and magnetic properties of Ni{sub 50}Mn{sub 37}Sn{sub 13} Heusler alloy ribbons

The Heusler alloy Ni50Mn37Sn13 was successfully produced as ribbon flakes of thickness around 7–10μm melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be MS=218K, Mf=207K, AS=224K, and Af=232K; the thermal hysteresis of the transformation is 15K. Ferromagnetic L21 bcc austenite phase shows a Curie point of 313K, with cell parameter a=0.5971(5)nm at 298K, transforming into a modulated 7M orthorhombic martensite with a=0.6121(7)nm, b=0.6058(8)nm, and c=0.5660(2)nm, at 150K.