A new interpretation of flow-stress measurements of high-purity NiAl below room temperature
A new interpretation of flow-stress measurements of high-purity NiAl below room temperature
复制标题
室温以下高纯 NiAl 流动应力测量的新解释
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
P. Gumbsch
中科院分区：
文献类型：
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作者：
D. Brunner;P. Gumbsch
摘要：采用恒应变速率ε˙$\dot{\varepsilon }$ p = 10-4 s-1，在77 ～ 325 K范围内测量了高纯NiAl单晶软取向（拉伸轴< 111 >附近）临界分解剪切应力（CRSS）与温度和应变速率的关系。在室温下预应变后，晶体在逐渐降低的温度下以Δεp≈0.005的应变增量发生塑性变形。在325 K以下，< 001 > {011}滑移体系的CRSS随温度的降低而缓慢升高，在200 K以下，CRSS的升高幅度更大。应力松弛实验测量的CRSS的应变率敏感性表现出类似的行为。热激活位错运动参数、激活体积和活化能表明，在200 K以上和200 K以下，不同的机制控制着位错运动。对于低应力，在200 K以上的温度下，建议在固溶体硬化理论的框架内解释结果。在200k以下，结果可以在流动应力扭结副理论的线张力模型框架内解释。对这些数据的评价得出扭结对能量为2Hk = 0.42 eV， peerls应力为535 MPa， peerls谷距等于晶格常数。这些数据通常与{110}或{100}个平面上扭结对形成的基本过程相一致。结果讨论了最近的原子模型的位错在NiAl。
Abstract The temperature and strain-rate dependence of the critical resolved shear stress (CRSS) of high-purity NiAl single crystals in soft orientation (tensile axis near 〈111〉) was measured in tensile tests with constant strain rate, ε˙ $\dot{\varepsilon }$p = 10–4 s–1, between 77 and 325 K. After pre-straining at room temperature, the crystals were plastically deformed by strain increments of Δεp ≈ 0.005 at successively decreasing temperatures. Below 325 K the CRSS on the 〈001〉{011} slip system slowly increases with decreasing temperature, followed by a steeper increase below about 200 K. The strain-rate sensitivity of the CRSS measured by stress-relaxation experiments exhibits comparable behaviour. The parameters for thermally activated dislocation motion, activation volume and activation energy, suggest that different mechanisms control the dislocation motion above and below 200 K. For low stresses, at temperatures above 200 K, an interpretation of the results within the framework of solid solution hardening theory is suggested. Below 200 K the results can be interpreted within the framework of the line-tension model of the kink-pair theory of flow stress. The evaluation of the data yields a kink-pair energy of 2Hk = 0.42 eV, a Peierls stress of 535 MPa, and a Peierls valley distance equal to the lattice constant. These data are generally compatible with a fundamental process of kink-pair formation on {110} or on {100} planes. The results are discussed with respect to recent atomistic modelling of dislocations in NiAl.