Numerical investigation elucidating effects of microstructure on the transient thermomechanical phenomena during laser impact welding
Numerical investigation elucidating effects of microstructure on the transient thermomechanical phenomena during laser impact welding
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DOI：
10.1016/j.jmapro.2022.04.031
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发表时间：
2022-07
影响因子：
6.2
通讯作者：
Glenn Gleason;Sumair Sunny;Ritin Mathews;A. Malik
中科院分区：
文献类型：
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作者：
Glenn Gleason;Sumair Sunny;Ritin Mathews;A. Malik
激光冲击焊接过程中发生的瞬态热力学现象，如极端塑性应变和温度峰值，由于连接过程的持续时间低于微秒，因此实验观察是不切实际的。因此，有必要建立计算模型来研究焊缝界面的原位行为。虽然研究人员已经利用计算模型进行此类研究，但这项工作阐明了微观结构水平建模的具体影响，该模型可以在较小的尺度上捕获相关的非均匀性/各向异性效应。采用欧拉框架对铝1100-H19飞片和不锈钢304-O靶箔进行了建模，模拟了不同金属箔激光冲击焊接过程中考虑和不考虑微观结构的情况。当考虑微观结构建模时，流动应力的变化表明，由于冲击压力集中在相对较小的晶粒处，沿焊缝界面的温度会间歇性升高；然而，它们并不是引发或影响关节形成的不稳定的重要来源。在焊缝界面附近10 μm厚的飞片区出现晶粒细化和材料硬化，靶区出现剧烈的塑性变形，表明可能发生马氏体相变。由屈服面变化驱动的晶界滑动导致了相对较高的碰撞速度。因此，在较高的温度下，较高的塑性应变率以及界面处较大数量的塑性散热导致材料喷射增加。每个模型都预测了交替瞬态剪应力，尽管非均匀模型预测了在反弹区域短暂出现集中剪切带，这在均匀模型中是看不到的。这项工作阐明了不同金属箔激光冲击焊接过程中微观结构和瞬态现象之间的相关性，从而证明了一种可扩展到许多其他在极短时间内完成的冲击焊接过程的数值模拟方法。
Transient thermomechanical phenomena such as extreme plastic strains and temperature spikes that occur during laser impact welding are impractical to experimentally observe given the sub-microsecond duration of the joining process. Thus, computational models are necessary to study in-situ behavior along the weld interface. While researchers have utilized computational models for such investigations, this work elucidates the specific influence of microstructure-level modeling that captures the associated inhomogeneity/anisotropic effects at smaller scales. An aluminum 1100-H19 flyer and a stainless steel 304-O target foil are modeled using an Eulerian framework to simulate cases with and without microstructure consideration during laser impact welding of dissimilar metallic foils. When considering microstructure modeling, variations in flow stress reveal intermittently elevated temperatures along the weld interface due to concentrations of shock pressure at relatively small grains; however, they are not found to be a significant source of instability initiating or influencing the joint formation. Grain refinement and material hardening are suggested within a 10 μm-thick zone of the flyer near the weld interface, while severe plastic deformation in the target indicates possible martensitic phase transformation. Grain boundary sliding driven by variations in yield surfaces among individual grains gives rise to relatively higher collision velocity. Consequently, higher plastic strain rates along with greater amounts of plastic heat dissipation at the interface result in increased material jetting at higher temperatures. Alternating transient shear stresses are predicted in each model, though the inhomogeneous model predicts the brief appearance of a concentrated shear zone in the rebound region which is not seen in the homogeneous model. This work illuminates correlations between microstructure and transient phenomena during laser impact welding of dissimilar metallic foils, thus demonstrating a numerical modeling approach extensible to numerous other impact welding processes that complete within a very short time span.