Structure changes of Co–Ni–Al ferromagnetic shape memory alloys after vacuum annealing and hot rolling

Abstract

The structure changes of vacuum annealed and hot rolled Co 35+ x –Ni 40− x –Al 25 ( x = 0, 2.5, 5.0) ferromagnetic shape memory alloys were examined by optical microscopy and X-ray diffraction measurements. Almost the same content of γ phase was observed in alloys after vacuum annealing. The change of grains morphology from dendrite in to equiaxed ones appeared after vacuum annealing. The hot rolling process was applied after annealing at 900 °C with thickness reduction up to about 90%. The structure of hot rolled samples revealed elongated grains of different phases. The hardness changes after heat treatment and plastic deformation processes have reflected the solution hardening and work hardening, respectively.