Deformation mechanisms of polycrystalline MoSi2 alloyed with 1 at.% Nb
Deformation mechanisms of polycrystalline MoSi2 alloyed with 1 at.% Nb
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DOI：
10.1016/s0921-5093(03)00307-1
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发表时间：
2003-10
期刊：
影响因子：
6.4
通讯作者：
A. Sharif;A. Misra;T. Mitchell
中科院分区：
文献类型：
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作者：
A. Sharif;A. Misra;T. Mitchell
二硅化钼(MoSi2)是一种高Peierls应力材料，在低同系温度下具有强烈的屈服应力温度依赖性。通过室温至1600℃压缩试验，研究了1 at.%Nb合金化对多晶MoSi2变形机制的影响。在≤900C下，多晶非合金MoSi2在塑性屈服之前断裂，但Nb合金化的MoSi2即使在室温下也可以在压缩下变形。透射电子显微镜研究表明，1 at.%Nb的存在增加了1/2〈_(111)〉位错的层错宽度，促进了1/2〈_(111)〉的低温滑移。溶液软化的解释是，随着部分间距的增加，部分位错(尤其是溶质原子附近的位错)更容易发生扭结形核。随着变形温度的升高，热激活使扭结形核变得容易，可能是由于溶质原子阻碍了扭结的迁移，导致了预期的高温固溶体硬化。在很高的温度下(∼1600°C)，含Nb合金的屈服强度可比纯MoSi2高一个数量级，并讨论了相关的硬化机制。
Molybdenum disilicide (MoSi2) is a high Peierls stress material with a strong temperature dependence of the yield stress at low homologous temperatures. We have investigated the effects of alloying with 1 at.% Nb on the mechanisms of deformation of polycrystalline MoSi2by compression testing from room temperature to 1600°C. While polycrystalline unalloyed MoSi2fractured before plastic yield at temperatures ≤900°C, the Nb-alloyed MoSi2could be deformed in compression even at room temperature. Transmission electron microscopy (TEM) investigations indicated that the presence of 1 at.% Nb increased the stacking fault width of 1/2〈111〉 dislocations and promoted 1/2〈111〉 slip at low temperatures. The solution softening is 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 is hindered by the solute atoms leading to the expected solid solution hardening at elevated temperatures. At very high temperatures (∼1600°C), the yield strengths of Nb-containing alloys may be up to an order of magnitude higher than pure MoSi2; the related hardening mechanisms are discussed.