Influence of grain boundaries with dispersed nanoscale Al2O3 particles on the strength of Al for a wide range of homologous temperatures
Influence of grain boundaries with dispersed nanoscale Al2O3 particles on the strength of Al for a wide range of homologous temperatures
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DOI：
10.1016/j.jallcom.2018.09.164
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发表时间：
2019-01-25
影响因子：
6.2
通讯作者：
Lavernia, Enrique J.
中科院分区：
文献类型：
--
作者：
Balog, Martin;Krizik, Peter;Lavernia, Enrique J.
研究了粉末冶金制备的超细晶(UFG)Al在较宽的相变温度(T-H)范围内的变形和强化行为。结果表明，主要位于高角度晶界(HAGBs)的高密度γ-Al_2O_3纳米粒子的存在促进了Al晶粒结构的显著稳定，T-H=0.94。对晶粒度(d(3d)分别为0.57、1.67、2.33和2.99微米的材料在600℃下热处理24 h后的0.2%应变偏置屈服应力(YS0.2)从室温到600℃进行了系统的研究。研究表明，随着d(3d)的减小，材料的应变硬化能力逐渐降低，而随着温度的升高，这种行为变得明显，这归因于塑性失稳的开始。材料在所有温度下的YS0.2符合YS0.2=a+kd(3d)(-0.5)关系。如在数据内插的基础上所确定的，在Rt时从已建立的Hall-Petch(HP)关系的正转变发生在d(3d)=类似于8微米处。由于参数a在Rt和300℃时为负值，因此文献记载的强度-结构关系不能基于Hall-Petch关系来解释。位于HAGB上的伽马-Al_2O_3颗粒对RT强化没有显著贡献，而Gb在整体强度中起着重要作用。这些材料显示出高达0.94的YS0.2。YS0.2与d3d的平方根倒数呈线性相关，系数k服从k=224.4-0.376 T关系。HP模型高估了温度升高时的YS0.2值，即对于d(3d)较小的材料。据认为，软化是由于伽马-Al_2O_3颗粒密集分布在3D网络中的结果，该颗粒包括在Hansen的强化模型中；颗粒强化在升高的T.(C)2018 Elsevier B.V.中发挥了作用。
The deformation and strengthening behavior of an ultra-fine grained (UFG) Al fabricated via powder metallurgy was investigated over a wide range of homologous temperatures (T-H). Our results reveal that the presence of a high density of gamma-Al2O3 nanoparticles, located primarily at high angle grain boundaries (HAGBs), promoted remarkable stabilization of the Al grain structure up to T-H = 0.94. The 0.2% strain offset yield stress (YS0.2) of the materials annealed at 600 degrees C for 24 h with grain sizes (d(3D)) of 0.57, 1.67, 2.33 and 2.99 mu m was systematically studied from room temperature (RT) to 600 degrees C. Our study reveals that with decreasing d(3D) the strain hardening ability of the materials gradually decreased, and this behavior became pronounced at elevated T, which was attributed to the onset of plastic instability. The YS0.2 of the materials at all T followed the relation YS0.2 = a + k d(3D)(-0.5). As determined on the basis of data interpolation, a positive transition from an established Hall-Petch (HP) relation at RT occurred at d(3D) = similar to 8 mu m. As the parameter a was negative at RT and 300 degrees C the documented strength-structure relationship cannot be explained on the basis of a Hall-Petch relation. The gamma-Al2O3 particles located at HAGBs did not contribute notably to RT strengthening, whereas GBs played a significant role in the overall strength. The materials showed a high YS0.2 up to a T-H of 0.94. The YS0.2 was observed to be linearly correlated with the reciprocal square root of the d3D and the coefficient k followed k = 224.4 -0.376 T relation. The HP model overestimated the YS0.2 values at elevated T namely for the materials with a smaller d(3D). It is proposed that softening occurred as a result of the gamma-Al2O3 particles densely distributed within a 3D network, which were included in Hansen's strengthening model; particle strengthening played a role at elevated T. (C) 2018 Elsevier B.V. All rights reserved.