【摘要】 采用TC4钛合金焊丝,在α钛合金、α+β钛合金和β钛合金表面进行电子束熔丝沉积增材成形试验,研究了异种材料增材成形时基材对成形层及附近材料的显微组织和硬度的影响规律。结果表明:成形层的宏观组织均是沿成形高度方向外延生长的粗大柱状晶,基材类型对柱状晶的尺寸有较大影响,TB5为基材时柱状晶尺寸较小;成形层的微观组织为典型的网篮组织,但以TA3为基材的成形层中α片层较为粗大且无马氏体α’相,以TC4为基材的成形层中片层α相的尺寸较小,而以TB5为基材的成形层中有α’相析出,且越靠近基材,α’相的尺寸越小,数量越多。在基材原表面附近的基材内部有一层过渡区域,其中部分金属在成形过程中被熔化。熔化区尺寸与基材类型有关,以TA3为基材时熔化区最小;过渡区内材料的硬度发生明显变化,尤其是以TB5合金作为基材、表面沉积TC4合金时,该区域的显微硬度高于TB5和TC4合金的硬度。研究表明,基材的热物理性能对成形过程中热传导的影响、合金元素含量对材料组织转变的影响,是过渡区域内熔化区尺寸、成形层与过渡层中组织与硬度变化的主要影响因素。更多还原

【Abstract】 Titanium alloy Additive Manufacturing was carried out by Electron Beam Wire Deposition on the surface of α-titanium alloy, α + β-titanium alloy and β-titanium alloy with the addition of TC4 titanium alloy welding wire. The effect of the substrate alloy on the microstructure and hardness in the forming layer and its adjacent materials was studied. The results shown that the macrostructure in the forming layer is the coarse columnar crystal growing along the forming height direction, and the substrate materials have a great influence on the size of the columnar crystal. With alloy TB5 as the substrate, the size of the columnar crystal perpendicular to the forming direction is small. The microstructure in the forming layer is a typical Basket-weave structure, but the size of the α sheet in the forming layer with alloy TA3 as the substrate is relatively large and free of martensite α’ Phase. The size of α phase in the forming layer with TC4 as the substrate is smaller than that in alloy TA3. While in the forming layer with alloy TB5 as the substrate, α’ phase is precipitated, and the closer to the substrate, the smaller the α’ size is and the more the number is. There is a transition region in the substrate near the original surface of the substrate, and some of the material near the surface is melted during the forming process. The size of the melting zone is related to the type of the substrate, and the hardness of the material in the transition zone is undulated obviously, especially when TB5 alloy is used as the substrate and TC4 alloy is deposited on the surface. The microhardness in this zone is higher than that of TB5 and TC4 alloy. The results show that the influence of the thermal physical properties of the substrate on the heat conduction and the alloy element content on the material structure transformation are the main factors affecting the melting zone size, the micro-structure and hardness in the forming layer and the transition layer.更多还原