Formation mechanism of nanocrystalline tungsten–titanium aluminides by ball milling of Ti(C,N)–W powders at subzero temperature

The effects of Al addition and milling at subzero temperatures on the transformation of Ti(C0.5N0.05)–W powder mixtures were investigated using XRD, SEM and TEM. Addition of Al powder improved the kinetics of solid solution between powder constituents. The effect of Al was ascribed to the increase of lattice strain at first stage milling process followed by the fast diffusion of atoms. The refinement of powder particles was not the determinant criteria for solid state dissolution. Multiple ternary compounds could be formed. Aluminium preferably reacted with tungsten. The W(Al,C) and W(Al,Ti) formed were stable, thus solubility of W in Ti(C0.5N0.05) in the presence of Al was limited.

Calculated microstrains e [%] and crystallite sizes L [nm] of W and Ti(C0.5N0.05) powders and the products milled at subzero temperature-indices (1) in Ti(C,N)–40%W mixtures and (2) in 55%Ti(C,N)–35%W–10%Al mixtures.Figure optionsDownload as PowerPoint slideResearch highlights
► The effects of Al and milling temperature of Ti(C,N)–W powder were investigated.
► The Al crystals were destroyed after short milling times and the atoms were dissolved in W lattices.
► The lattice strain of W(Al) increased at short milling time.
► The relaxation of W(Al) lattice strain enhanced the formation of the ternary W(Al,C), W(Al,Ti) and Ti(W,C).
► W–Al compounds were stable and dissolution of W in the Ti(C,N) was limited.