It was recalled that this was a high Peierls stress material, with a strong temperature dependence of the yield stress at low homologous temperatures. An investigation was made of the effects of alloying with 1at%Nb upon the mechanisms of deformation of polycrystalline MoSi2 by compression testing from room temperature to 1600C. While polycrystalline unalloyed MoSi2 fractured before plastic yield at up to 900C, the Nb-alloyed MoSi2 could be deformed in compression even at room temperature. Transmission electron microscopic investigations indicated that the presence of 1at%Nb increased the stacking fault width of ½<111> dislocations and promoted ½<111> slip at low temperatures. The solution softening was interpreted in terms of easier kink nucleation on partial dislocations (especially in the vicinity of solute atoms) with increasing partial spacing. With increasing deformation temperature, thermal activation makes kink nucleation easy, and presumably, kink migration was hindered by the solute atoms leading to the expected solid solution hardening at elevated temperatures. At very high temperatures (~1600C), the yield strengths of Nb-containing alloys may be up to an order of magnitude higher than pure MoSi2.

Deformation Mechanisms of Polycrystalline MoSi2 Alloyed with 1at%Nb. A.A.Sharif, A.Misra, T.E.Mitchell: Materials Science and Engineering A, 2003, 358[1-2], 279-87