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Modelling the transition from strengthening to softening due to grain boundaries

机译:模拟由于晶界从强化到软化的过渡

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Published data on pure Cu at or close to its saturation state of deformation suggests a Hall-Petch relation of flow stress at ambient temperature in the range of grain sizes 1 μm > d > 10 nm [W. Blum, Y.J. Li, J. Chen, X.H. Zeng, K. Lu, Int. J. Mater. Res. 97 (2006) 1661-1666] while for elevated temperatures ultrafine-grained Cu produced by severe plastic deformation exhibits softening relative to conventional grain sizes d > 10 μm [Y.J. Li, X.H. Zeng, W. Blum, Acta Mater. 52 (2004) 5009-5018]. Presuming grain boundaries as impenetrable dislocation obstacles, these observations are rationalized by (i) a reduction of the mean slipped area and corresponding shift in the main location for dislocation storage from grain interior to boundaries with decreasing d; (ii) thermally activated dissolution of dislocation dipoles occurring faster at boundaries than within the grain interior owing to different coefficients of diffusion. A simple statistical dislocation model is derived from these ideas and compares to experimental results in semi-quantitative agreement.
机译:关于纯铜处于或接近其饱和变形状态的已发布数据表明,在环境温度下,在1μm> d> 10 nm的晶粒尺寸范围内,流应力的霍尔-帕奇关系[W.百隆,李玉洁,陈建勋。曾庆国J. Mater。 Res。 97(2006)1661-1666],而在高温下,由于剧烈的塑性变形而产生的超细晶粒Cu相对于常规晶粒尺寸d> 10μm表现出软化作用。李小华曾(Weng Blum),Acta Mater。 52(2004)5009-5018]。假定晶界是难以理解的位错障碍,可以通过以下方式使这些观察合理化:(i)减小平均滑移面积并相应地在主要位置将位错存储的主要位置从晶粒内部转移到晶界到d减小; (ii)由于扩散系数不同,位错偶极的热活化溶解在边界处比在晶粒内部发生的快。从这些思想中得出了一个简单的统计错位模型,并与半定量协议的实验结果进行了比较。

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