大厚度Ti-6Al-4V ELI钛合金电子束焊接头的组织及力学性能

Microstructure and Mechanical Properties of Electron Beam Welded Large Thickness Ti-6Al-4V ELI Alloy

采用不同的焦点偏移量和扫描幅值对55 mm厚Ti-6Al-4V ELI钛合金板进行电子束焊接试验,通过金相分析、室温拉伸及显微硬度测试,研究了焊缝成型及接头的组织、力学性能。结果表明:当采用较小的焦点偏移量焊接时,扫描幅值的增加会显著降低焊缝深宽比,当焦点偏移量过大时,焊缝易出现咬边及明显的钉尖缺陷。焊缝组织为粗大的柱状晶,其内部由十字交叉状排列的针状马氏体α’相构成。当焦点偏移量为-15 mm、扫描幅值为0.2 mm时,接头抗拉强度比母材的高,沿熔深方向抗拉强度无明显差异,力学性能稳定。焊缝处平均硬度为323 HV,比母材高40 HV。

The electron beam welding tests of 55 mm thick Ti-6Al-4V ELI titanium alloy plates were carried out by using different defocusing distances and scanning amplitudes,and the weld forming,the microstructure and properties were investigated through metallographic analysis,tensile test at room temperature and microhardness test.The results show that when small defocusing distance is used for welding,increasing the scanning amplitude significantly reduces the depth to width ratio of the weld,and when the defocusing distance is big,undercut defects and obvious spiking defects are easy to appear in the weld bead.The weld microstructure is thick columnar crystals,and the interior of the crystals is composed of acicular martensite α'phase arranged in a cross pattern.When the defocusing distance is -15 mm,the scanning amplitude is 0.2 mm,the tensile strength of the welded joint is higher than that of the base metal,and there is no obvious difference of tensile strength along the depth direction.The mechanical properties of the welded joint are stable.The microhardness of the weld zone is 323 HV,which is 40 HV higher than that of the base metal.