TC4钛合金激光叠焊成形及显微组织

Research on Microstructure and Formation Characteristic of Laser Welded Lap Joints of TC4 Titanium Alloy

研究TC4钛合金激光叠焊成形及焊缝显微组织特征,提出表征叠焊接头焊合程度的指标——焊合率ψ。研究结果表明:焊缝熔宽随着激光功率的升高和焊接速度的降低逐渐增加,上板焊缝熔宽大于下板焊缝,而连接焊缝处的熔宽最小;焊合率随着叠焊两板间间隙的增加或焊接线能量的升高而降低;焊缝组织为针状马氏体α′组成的"网篮"组织,上板焊缝中马氏体分布更密集;热影响区中存在少量细小马氏体组织,且呈梯度分布。由于马氏体的界面增强效应,使焊缝横向显微硬度沿焊缝中心向母材逐渐降低,且上板焊缝显微硬度略高于下板焊缝。

Microstructure and formation characteristic of laser welded lap joints of TC4 alloy were investigated, and a parameter named join rate ψ was introduced to evaluate the welding effect of lap welding. The results indicated： the width of weld bead increases with increasing laser power or decreasing welding velocity, the top width of weld bead is larger than the bottom width and the minimum is the middle layer. And the join rate decreases as plates space or energy input increases. Microstructure of weld bead consisted of α＇ martensite, and the martensite in the top portion is more concentrate than that in the bottom portion. There ate a small amount of martensite in HAZ, and distributed in gradient. For the strengthen effect of martensite, the microhardness reduces from the center of joints to base metal in cross direction, and the microhardness is higher in top weld bead.