STRUCTURAL CHARACTERIZATION OF Ti-18Si-6B AND Ti-7.5Si-22.5B ALLOYS PROCESSED BY HIGH-ENERGY BALL MILLING AND HOT PRESSING

This work presents the preparation of Ti-18Si-6B and Ti-7.5Si-22.5B (at.-%) alloys by high-energy ball milling and subsequent hot pressing from high-purity powders. The milling was carried out in a Fritsch P-5 mill under argon atmosphere, rotary speed of 200 rpm, stainless steel vials/balls, and with a ball-to-powder weight ratio of 10:1. The milled powders were precompacted by uniaxial pressing, and subsequently consolidated by vacuum hot pressing in order to obtain bulks. The phase transformations during ball milling and after consolidation by hot pressing by means of X-rays diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS) were evaluated. XRD experiments indicate that the silicon peaks disappear in the milled powders due to the silicon atoms dissolution into the titanium lattice. In addition, it is noted a halo formation during milling of the both powder mixtures. After hot pressing, peaks of Ti+Ti6Si2B+Ti5Si3 and Ti+Ti6Si2B+TiB are identified in Ti-18Si-6B and Ti-7.5Si-22.5B (at.-%) alloys, respectively. Iron contamination lower than 6 wt.-% was measured by EDS analysis.