The viscoplastic behavior of coarse and bimodal fine/ultrafine grained (F/UFG) Al5083 alloy was investigated between 20 °C and 200 °C through tensile tests at various strain rates, and stress relaxation tests to deduce the strain rate sensitivity (SRS). The plastic strain fields were measured by correlation of SEM images. In the F/UFG material at high temperature, very high strains were measured in shear bands which sometimes crossed the whole gage width and exhibited intensive grain boundary sliding (GBS). Both the SRS and ductility rose with the temperature, and as the strain rate decreased, mainly due to a rising contribution of GBS, which accommodated a much larger fraction of the global strain in the F/UFG material. The boundary between the temperature–strain rate domains where grain refinement led either to strengthening or to softening was determined. Finite element simulations of tension and relaxation tests with viscoplastic grains and sliding grain boundaries captured the macro-scale behavior of the F/UFG material. It also provided some insight into the mechanisms of correlated and cooperative GBS and grain rotation along percolation paths (both inter and intragranular), probably, responsible for macro shear banding.

中文翻译：

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粗粒和细粒/超细粒5083铝合金的晶界滑动和应变速率敏感性

通过在各种应变速率下进行拉伸测试以及应力松弛测试以推断应变速率敏感性（SRS），在20°C至200°C之间研究了粗粒和双峰细/超细晶粒（F / UFG）Al5083合金的粘塑性行为。通过SEM图像的相关性来测量塑性应变场。在高温下的F / UFG材料中，在剪切带中测得的应变很高，该剪切带有时会跨越整个量规宽度并表现出强烈的晶界滑动（GBS）。SRS和延性都随温度而升高，并且随着应变率的降低而增加，这主要归因于GBS的贡献增加，GBS吸收了F / UFG材料中全球应变的很大一部分。确定了温度-应变率域之间的边界，在该边界处晶粒细化导致强化或软化。用粘塑性颗粒和滑动晶界进行的拉伸和松弛试验的有限元模拟，捕获了F / UFG材料的宏观行为。它还提供了有关GBS相关和合作GBS以及沿渗流路径（颗粒间和颗粒内）旋转的晶粒的机制的一些见解，这可能是造成宏观剪切带的原因。