激光焊接Ti-6Al-4V钛合金塑性行为的原位SEM/EBSD分析（英文）

In-Situ SEM and EBSD Analysis on Plastic Behavior of Laser Beam Welding Ti-6Al-4V Alloy

选用原位SEM/EBSD显微术分析研究了Ti-6Al-4V钛合金的焊接区域的变形行为。研究发现,由于焊接时高的焊接温度(在β相变点之上)和急剧的冷却速率,导致β→α'马氏体相变的发生。SEM观察发现,在焊缝区只存在有针状的α'马氏体形貌,而在焊接第一热影响区和第二热影响区,针状α'相逐渐发生球化,形成了明显的显微组织梯度过渡。在对焊接区域进行SEM/EBSD下的原位拉伸实验后发现,该区域的塑性变形可划分为两个阶段。变形的第一阶段,滑移变形或孪生变形均有可能发生,这取决于晶粒的初始晶体学取向是否可通过旋转来匹配<120>//TA(拉伸方向);而在变形的第二阶段,只发生滑移变形。

EBSD and in-situ SEM were used to study the plastic behavior of laser beam welding Ti-6Al-4V.Due to the high weld temperature(exceeding theβ-transus)and high cooling rate,β→α′martensitic transformation occurs.Within the fusion zone,only acicular morphology exists,while in1 st heat affected zone(HAZ)and 2 nd HAZ,these acicular laths globalize,which show an obvious microstructural gradient.The result of the in-situ plastic deformation shows the deformation can be divided into 2 stages.In the first stage of the deformation,either slipping or twinning can occur.It depends on whether the initial orientation can respect<120>//TA(tensile axis)by rotating the grains or not.While in the second stage,only slipping can be found.