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首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Plastic deformation of nickel under high hydrostatic pressure
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Plastic deformation of nickel under high hydrostatic pressure

机译：高静水压力下镍的塑性变形

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摘要

Samples of nickel were deformed in torsion under very high hydrostatic pressures (up to 8 GPa) up to strains being much larger than those reached under normal pressure conditions. The obtained stress-strain curves were fitted by the model of Zehetbauer and Kohout which has been developed from the work hardening model of Zehetbauer designed for conventional large strain deformation. The configuration parameters of dislocations were determined from strain dependent dislocation densities which were measured by Multiple Whole X-ray Bragg Peak Profile Analysis (MXPA). Using actual materials and physical constants of Ni, the obtained values of fitting parameters could be related to realistic numbers of physical quantities hidden in those.The main part of the deformation stress increase observed with increasing hydrostatic pressure can be ascribed to the increase of dislocation density which arises from the restriction of diffusion controlled annihilation mechanisms. This restriction is related to the pressure-induced decrease of diffusion, i.e. to the increase of vacancy migration enthalpy which is due to the shrinking of interatomic spacing when the hydrostatic pressure is enhanced.However, the calculated concentrations of deformation induced vacancies for pressures 5 GPa and beyond are unacceptably high. Data from measurements of microhardness and MXPA after unloading show that beyond a pressure of 4 GPa both the strength and the dislocation density is not being increased anymore which suggests the onset of spontaneous vacancy and dislocation annihilation due to the high overall concentration of vacancies reached. This failure of the model is not surprising since it has not considered so far any limits in the vacancy concentration.
机译：镍样品在非常高的静水压力（高达8 GPa）下扭曲变形，其应变远大于在常压条件下达到的应变。得到的应力-应变曲线由Zehetbauer和Kohout的模型拟合，该模型是从Zehetbauer的工作硬化模型开发的，该模型是为常规大应变变形设计的。位错的构型参数是由应变依赖性位错密度确定的，该密度是通过多次全X射线布拉格峰轮廓分析（MXPA）测量的。利用Ni的实际材料和物理常数，拟合参数的取值可能与其中隐含的实际物理量有关。随着静水压力的增加，观察到的变形应力增加的主要原因可以归因于位错密度的增加。这是由于扩散控制的hil灭机制受到限制而引起的。这种限制与压力引起的扩散减少有关，即与空位迁移焓的增加有关，空位迁移焓的增加是由于在增加静水压力时原子间距的缩小。但是，在压力为5 GPa时，计算得出的变形引起的空位的浓度甚至更高。卸载后显微硬度和MXPA的测量数据表明，超过4 GPa的压力后，强度和位错密度都不再增加，这表明由于空位的总体集中度很高，因此出现了自发空位和位错an灭。该模型的失败不足为奇，因为到目前为止尚未考虑空位浓度的任何限制。

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