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Zhang, X. X.*; Lutz, A.*; Andr
, H.*; Lahres, M.*; Gong, W.; Harjo, S.; Emmelmann, C.*
Journal of Alloys and Compounds, 898, p.162890_1 - 162890_8, 2022/03
被引用回数：10 パーセンタイル：62.14(Chemistry, Physical)The ductility of the Al alloys produced by additive manufacturing (AM) has become a critical property, as the AM Al alloys are increasingly used in the automotive industry. However, the ductility of as-built AM Al alloys is relatively low, even with optimized AM conditions. The post-annealing treatment provides an efficient way to improve ductility. Previous investigation has shown that the annealed AM AlSi3.5Mg2.5 alloy possesses superior ductility. However, the plastic deformation micro-mechanisms of the annealed AM AlSi3.5Mg2.5 alloy remain unclear. In this study, in-situ neutron diffraction was employed to explore the annealed AM AlSi3.5Mg2.5 alloy. The evolutions of phase stresses, dislocation density, and crystallite size in the annealed AM AlSi3.5Mg2.5 alloy during tensile deformation were analyzed. The experimental investigation reveals that the dislocation density in the Al matrix of the annealed AM AlSi3.5Mg2.5 alloy increases slowly in the early plastic deformation stage, and it reaches a saturated level upon the following uniform deformation. The crystallite size decreases quickly in the early deformation stage, and then it decreases slowly. The Kocks-Mecking model and the Voce model can capture the strain hardening behavior well. The determined physical constitutive equations can be applied in continuum mechanical computer simulations.
Zhang, X. X.*; Knoop, D.*; Andr, H.*; Harjo, S.; 川崎 卓郎; Lutz, A.*; Lahres, M.*
International Journal of Plasticity, 140, p.102972_1 - 102972_20, 2021/05
被引用回数：47 パーセンタイル：95.10(Engineering, Mechanical)To better understand and predict the mechanical properties of additive manufacturing (AM) Al-Si-Mg alloys, developing a physically-based constitutive model is crucial. Among different models, the dislocation-density-based Kocks-Mecking (K-M) constitutive model has been widely used. In-situ neutron diffraction, a powerful method to measure the phase stress and dislocation density in bulk polycrystalline materials under loading, is employed to investigate the AM AlSi3.5Mg1.5 and AlSi3.5Mg2.5 (wt.%) alloys. Based on the present measured and previous experimental data, a multiscale constitutive model is developed for different AM Al-Si-Mg alloys.
Zhang, X. X.*; Andr, H.*; Harjo, S.; Gong, W.*; 川崎 卓郎; Lutz, A.*; Lahres, M.*
Materials & Design, 198, p.109339_1 - 109339_9, 2021/01
被引用回数：58 パーセンタイル：93.33(Materials Science, Multidisciplinary)Here, in-situ neutron diffraction is employed to explore the residual strains, stresses, and dislocation density in the LPBF AlSi10Mg during loading-unloading-reloading deformation. It is found that the maximum residual stresses of the Al and Si phases in the loading direction reach up to about -115 (compressive) and 832 (tensile) MPa, respectively. A notable dislocation annihilation phenomenon is observed in the Al matrix: the dislocation density decreases significantly during unloading stages, and the amplitude of this reduction increases after experiencing a larger plastic deformation. At the macroscale, this dislocation annihilation phenomenon is associated with the reverse strain after unloading. At the microscale, the annihilation phenomenon is driven by the compressive residual stress in the Al matrix. Meanwhile, the annihilation of screw dislocations during unloading stages contributes to the reduction in total dislocation density.
