Microstructure of stainless steel single-crystal electron beam welds
Microstructure of stainless steel single-crystal electron beam welds
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DOI：
10.1007/bf02672592
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发表时间：
1990-06
期刊：
影响因子：
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通讯作者：
S. David;J. Vitek;M. Rappaz;L. Boatner
中科院分区：
文献类型：
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作者：
S. David;J. Vitek;M. Rappaz;L. Boatner
作者以前开发的焊缝显微组织分析技术，包括生长晶体学和熔池形状的影响，适用于几种情况下，涉及单晶电子束焊接的Fe-15 Ni-15 Cr合金。焊缝显微组织和相关枝晶生长模式的评估是基于三维（3-D）几何分析。本研究包括检查重叠，多道自焊焊缝和对接焊缝的两个单晶具有不同的取向，以及由于焊接速度的变化的影响所观察到的效果。熔池形状被发现改变显着增加焊接速度变得更窄的横截面，但在焊接方向上更细长。此外，所有电子束焊接显示出焊池中心的平台区域的证据。然而，池的形状，被发现是独立的结晶取向。因此，可以将熔池形状结果扩展到以任何取向焊接的晶体，甚至多晶体。重叠多道焊缝显示出显着的再现性，从通过到通过和复制的结构模式中发现的单道焊缝。在每个通道内的树枝状图案的相似性表明，熔池形状是相同的，在所有的通行证。具有不同相对取向的两个单晶的对接焊缝的显微组织显示出与每个单独的晶体学取向相关联的显著关系，并且显微组织实际上是两个单道次显微组织的简单复合物。还检查了其他微观结构细节。枝晶分支的趋势与从一个枝晶生长方向到另一个的过渡有关。还发现，未熔透焊缝在焊缝底部有一个小突起。有人建议，焊接熔池形状的建模可以直接评估通过比较预测的枝晶生长模式的基础上建模的形状与实际实验观察到的枝晶生长模式。
Previously developed techniques by the authors for the microstructural analysis of welds, that included the effects of both the growth crystallography and the weld pool shape, are applied to several cases involving the single-crystal electron beam welding of an Fe-15Ni-15Cr alloy. This evaluation of weld microstructures and associated dendritic growth patterns is based on a three-dimensional (3-D) geometrical analysis. The present study includes examination of the effects observed in overlapping, multipass autogenous welds and butt welds of two single crystals with different orientations, as well as effects due to variations in the welding speed. Weld pool shapes were found to change significantly with increasing welding speed—becoming narrower in cross section but more elongated in the welding direction. Additionally, all electron beam welds showed evidence of a plateau region in the center of the weld pool. The pool shapes, however, were found to be independent of the crystallographic orientation. Therefore, it is possible to extend the pool shape results to crystals welded in any orientation and even to polycrystals. The over-lapping multipass welds showed remarkable reproducibility from pass to pass and duplicated the structural patterns found in single-pass welds. The similarity in dendritic patterns within each pass indicated that the weld pool shapes were identical in all of the passes. The micro-structure of butt welds of two single crystals with different relative orientations showed a remarkable relationship to that associated with each individual crystallographic orientation, and the micro structure was, in effect, simply a composite of two single-pass microstructures. Additional microstructural details were also examined. The tendency toward branching of dendrites was associated with the transition from one dendrite growth orientation to another. It was also found that the nonpenetrating welds exhibited a small protrusion at the bottom of the weld. It is suggested that the modeling of weld pool shapes can be directly evaluated by comparing the predicted dendritic growth patterns based on the modeled shapes with the actual experimentally observed dendritic growth patterns.