Abstract

The microstructure of double-sided welded joints of 3D-printed items made of titanium alloy Ti‒6Al–4V by the electron-beam freeform fabrication (EBF³) method has been investigated using the methods of X-ray diffraction analysis, optical metallography, and scanning and transmission electron microscopy. It is found that columnar epitaxial growth of primary β grains with transverse dimensions close to the sizes of primary β grains in the base material occurs in the process of electron-beam welding with a double-sided welded joint. Inside the primary β grains, there are grains of the α-phase with a lamellar shape inherited from the α' martensite, which is formed in the course of transformation β → α'. As in the printed samples, there is a nanocrystalline α"-phase in the metal of the welded joint inside grains of the α-phase and in interlayers of the β-phase. However, the density of particles of this phase in the metal of the welded joint is higher than in the base material. In the metal of the welded joint, tensile macrostresses and elastic residual microstrains also increase. The microhardness of the metal of the welded joint is greater than the microhardness of the base material.

中文翻译：

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电子束焊接对钛合金Ti-6Al-4V的3D打印产品的组织和显微硬度的影响

摘要

钛合金Ti‒6Al–4V制成的3D打印件的双面焊接接头的微观结构，电子束自由成形（EBF ³）方法已使用X射线衍射分析，光学金相学以及扫描和透射电子显微镜的方法进行了研究。发现在与双面焊接接头的电子束焊接过程中，发生横向尺寸接近于母材中的初生β晶粒尺寸的初生β晶粒的柱状外延生长。在一次β晶粒内部，存在着从α'马氏体继承而来的层状形状的α相晶粒，这些晶粒是在转变β→α'的过程中形成的。如印刷样品中所示，在α相的晶粒内部和β相的中间层中，焊接接头的金属中存在纳米晶的α“相。焊接接头高于母材。在焊接接头的金属中，拉伸大应力和弹性残余微应变也会增加。焊接接头的金属的显微硬度大于基材的显微硬度。