厚板TC4钛合金电子束焊接头组织和力学性能研究

Study on Microstructure and Properties of Thick TC4 Alloy Joints Welded by Electron Beam

对30 mm厚TC4钛合金进行电子束焊接试验,通过金相分析以及显微硬度测试对焊接接头的显微组织和力学性能进行了研究。结果表明,TC4钛合金母材由等轴α以及部分β转变组织组成,焊缝区组织在纵向上具有不均匀性。焊缝顶部β柱状晶粗大,沿熔合线向顶部生长,中部和下部柱状晶相对较小,垂直熔合线向焊缝中心对称竞相生长。β晶粒内部微观组织为针状马氏体,马氏体尺寸从焊缝顶部到底部逐渐减小。热影响区显微组织为等轴初生α相和α'针状马氏体,以及未完全转变的β相。焊缝区和热影响区显微硬度值高于母材;在焊缝区纵向上,顶部显微硬度值为340 HV,随着距离焊缝顶部距离的增加,硬度值显著增大,最大值为435 HV。

TC4 alloys with the thickness of 30mm were welded by the electron beam, and the microstructure and properties of the joints were investigated through metallographic analysis and microhardness test. The results show that the microstructure of the base metal is composed of equiaxed α phase and the other transformed from the primary coarse β phase, and the microstructure of the welded zone has inhomogeneity in the depth direction. The β phase columnar grains in the top of the welds are relatively coarse, and grow up along with the fusion line to the top,while the sizes of the microstructure in the middle and the bottom decrease successively, and the growth direction is perpendicular to the fusion line until the weld center. The internal microstructure of β grains is acicular martensite, whose sizes decrease successively from the top to the bottom of welding line. The micrstructure of the HAZ is the mixture of equiaxed α phase and fine acicular martensite and incomplete transition βphase. The microhardness of weld zone and HAZ is higher than that of the base metal. The microhardness value on the top of weld zone is 340 HV in the depth direction. With the increase of distance from the bottom to the top of welding line, the microhardness value increases markedly, the maximum is 435 HV.