High-energy ball milling of Ni-Ti and Ni-Ti-Nb powders

Author(s)

Martins, C. B. ; Silva, G. ; Fernandes, B. B. ; Ramos, E. C. T. ; Mardegan, D. A. ; Ramos, A. S. ; Salgado, L ; Filho, FA

• Document type: Journal article
• Source: Materials Science Forum; v. 530-531, p. 2-pg., 2006-01-01.

Abstract

This work reports on the preparation of Ni-50Ti and Ni-40Ti-10Nb and Ni-30Ti-20Nb (at.%) powders by high-energy ball milling and subsequent heat treatment. The milling process was carried out at room temperature in a planetary ball mill under Ar atmosphere. The as-milled powders were than heat-treated at 900 degrees C for 1h under Ar atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), and microanalysis via energy dispersive spectroscopy (EDS) were used to characterize the milled and heat-treated powders. A metastable phase was initially formed in Ni-50Ti and Ni-40Ti-10Nb powders milled for 1h. Following the ball milling, the B2-NiTi compound was formed in these powder mixtures. The disordering of the B2-NiTi compound occurred owing the internal lattice strain after milling for 30h. Two phases were identified in Ni-50Ti and Ni-40Ti-10Nb powders milled for 60h: the metastable phase previously reported, and an amorphous phase. In Ni-30Ti-20Nb powders, it was noted the presence of an amorphous halo only. A structural relaxation of the B2-NiTi phase occurred in heat-treated Ni-50Ti, Ni-40Ti-10Nb, and Ni-30Ti-20Nb powders. A small amount of Ni3Ti and NiTi2 was also formed after heat treatment at 900 degrees C for I h, and an iron contamination lower than 2at.% was found. (AU)