Formation and thermal properties of nanoscale Ti50Ni40Fe10 produced by mechanical alloying

Abstract

The formation and thermal stability of nanoscale Ti50Ni40Fe10 powder produced by mechanical alloying was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential calorimetry (DSC), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The composition of the alloys was determined using inductively-coupled plasma emission spectrometry (ICP). Up to 300 h leads were milled to an almost broad diffraction hump near 2θ = 43.80°. The crystallite size, calculated using the Williamson-Hall and Scherrer methods, decreased with the milling time tm. The internal strain was about 3.19 × 10−3 for 30 h of milling. The entire mechanical alloying process can be divided into three stages: agglomeration (0 < tm ≤ 50 h), disintegration (50 < tm < 300 h), and homogenization (300 ≤ tm ≤ 400 h). The crystallite size and the saturation magnetization Ms reached values of about 2.4 nm and 5.4 emu/g at 300 h, respectively. The values of Tp and Tx were about 446.8 °C and 413.1 °C, respectively. In isothermal experiments, the signal decayed monotonically, demonstrating that the transformation process was partially a grain growth type. The peaks of NiTiO3, FeNi3, and TiO2, were observed in the XRD pattern after annealing at 1000 °C.