Effect of mechanical alloying on the microstructure and properties of W–Ti alloys fabricated by spark plasma sintering

Abstract

W–15wt.% Ti alloys were fabricated through mechanical alloying with different milling times ranging from 10h to 80h. The powders milled for 10, 30, 60, and 80h were sintered by spark plasma sintering at 1600°C. The milled powders and sintered samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; and their microhardness and thermal conductivity were investigated. Results revealed that the particles underwent welding, fracturing, and rewelding when the milling time increased. The grain size decreased, whereas the microstrain increased from 0.344% at 10h to 0.543% at 80h and dislocation density increased with the increase in milling time. However, the WC contamination was induced into the powder after a long milling time, thereby possibly forming the (Ti,W)C1−x solid solution with the addition of Ti after sintering. The second phase became uniformly distributed and the W grain size was reduced from 1.48μm to 0.31μm after a long milling time. Furthermore, the Vickers hardness increased from 543.05Hv to 890.30Hv and thermal conductivity also increased with an increase in milling time.