On Ti-18Si-6B and Ti-7.5Si-22.5B powder alloys prepared by high-energy ball milling and sintering

Abstract

Recently, a new ternary phase was discovered in the Ti-Si-B system, located near the Ti 6 Si 2 B composition. The present study concerns the preparation of titanium alloys that contain such phase mixed with α-titanium and other intermetallic phases. High-purity powders were initially processed in a planetary ball-mill under argon atmosphere with Ti-18Si-6B and Ti-7.5Si-22.5B at. (%) initial compositions. Variation of parameters such as rotary speed, time, and ball diameters were adopted. The as-milled powders were pressureless sintered and hot pressed. Both the as-milled and sintered materials were characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive spectrometry. Sintered samples have presented equilibrium structures formed mainly by the α-Ti+Ti 6 Si 2 B+Ti 5 Si 3 +TiB phases. Silicon and boron peaks disappear throughout the milling processes, as observed in the powder diffraction data. Furthermore, an iron contamination of up to 10 at. (%) is measured by X-ray spectroscopy analysis on some regions of the sintered samples. Density, hardness and tribological results for these two compositions are also presented here.

Study of Ti-7.5Si-22.5B alloys produced by powder metallurgy

“…However, hardness and densification increase significantly when HP is used, as shown in previous research using current-activated pressure-assisted sintering (CAPAS) [7] . Densification of the Ti-7.5Si-22.5B powders was improved due to the use of powders milled for only 1 hour comparing with HP of elemental powders without milling 20 . This phenomenom is explained in other papers 9,12 .…”