Laser welding was performed on a U6wt%Nb uranium alloy using a 400 W solid state laser with welding speeds from 20 to 2500 mm/s. This speed range spanned melt pool sizes from traditional welding to surface modification and additive manufacturing. With increasing scan speed, the ratio of weld length relative to depth and width increased, with melt pool lengths being more than 5x greater than the width and 10x greater than the depth at the highest speeds. Keyhole mode welds were shown to occur at low speeds, while conduction mode welds occurred at 700 mm/s or higher as the weld depth dropped off more rapidly than width at higher speeds. Microstructures that form at the boundary between the fusion zone and base metal were observed to have a nonconventional appearance consisting of interpenetrating dark and light contrast phases before cells or dendrites appear. Dendrites with secondary arms form from this boundary in keyhole welds and refine to no visible secondary arms near the weld center. Primary and secondary dendrite arms, where present, were shown to refine in size inversely with cooling rate raised to the 0.465 and 0.375 powers respectively. Dendrites were largely absent from the conduction mode welds at higher speeds, and were replaced by a banded microstructure that appears to form by an oscillatory solidification front mechanism.

使用400 W固态激光器在U6wt％Nb铀合金上进行激光焊接，焊接速度为20到2500 mm / s。该速度范围涵盖了从传统焊接到表面改性和增材制造的熔池大小。随着扫描速度的提高，焊缝长度与深度和宽度的比值增加，在最高速度下，熔池长度比宽度大5倍以上，比深度大10倍。锁孔模式焊缝在低速时发生，而传导模式焊缝在700 mm / s或更高时发生，这是因为在高速焊缝中，焊缝深度比宽度下降得更快。观察到在熔合区和贱金属之间的边界处形成的微结构具有非常规的外观，该非常规的外观由在细胞或树突出现之前互穿的暗和亮对比相组成。在锁孔焊缝中从该边界形成带有次级臂的枝晶，并细化到在焊接中心附近没有可见的次级臂。初级和次级枝晶臂，如果存在的话，显示尺寸反比地细化，冷却速率分别提高到0.465和0.375幂。在较高速度下，传导模式焊缝中基本上不存在枝晶，而由似乎由振荡凝固前沿机制形成的带状微结构代替。初级和次级枝晶臂，如果存在的话，显示尺寸反比地细化，冷却速率分别提高到0.465和0.375幂。在较高速度下，传导模式焊缝中基本上不存在枝晶，而由似乎由振荡凝固前沿机制形成的带状微结构代替。初级和次级枝晶臂，如果存在的话，显示尺寸反比地细化，冷却速率分别提高到0.465和0.375幂。在较高速度下，传导模式焊缝中基本上不存在枝晶，而由似乎由振荡凝固前沿机制形成的带状微结构代替。