预热温度对GTA增材制造钛铝合金组织及性能的影响

Influences of preheating temperatures on the microstructures and mechanical properties of GTA additive manufactured TiAl based alloy

高温结构材料TiAl金属间化合物的可加工性较差,复杂结构成形技术难度大,制造成本高.电弧增材可以实现TiAl基合金的原位低成本柔性制造,但制造过程中仍需注意裂纹控制问题.预热处理通过改善组织可以有效抑制裂纹产生.文中以Ti6Al4V与ER1100纯铝焊丝作为原材料,在200,300,450℃的预热温度下利用TIG焊原位合成了铝含量为50%(原子分数)的TiAl基合金,考察了不同预热温度下TIG电弧增材制造的钛铝合金的组织与力学性能.结果表明,随着预热温度的增加,构件的顶部与中部区域逐渐在γ/α2层片团的晶界析出更多的块状γ相,底部组织变化不明显.预热温度的增加使得合金中γ相增多而α2相减少,导致合金室温硬度减少.同时,弥散分布的块状γ相的增多,使得构件的压缩性能提升,当预热温度为450℃时,构件抗压强度与压缩率最高.

High-temperature structural material TiAl based alloy has poor machinability. It is challenging to fabricate complex structures. And the processing cost is relatively high.GTA arc additive manufacturing is a promising technology to synthesis Ti Al based alloy in situ with increased flexibility and low cost. However, crack control is still essential during fabrication. Preheating is effective in avoiding cracking during additive manufacturing. In this work, the Ti6Al4V and ER1100 wires are used as feedstock to fabricate Ti Al based alloy in situ with an aluminum content of 50 at%. Preheating temperatures of 200, 300, 450 ℃ are used to investigate the influences on the microstructures and mechanical properties of the fabricated specimen. Results show that, with the preheating temperature increasing, more bulk γ phases precipitate on the boundaries of γ/α2 lamellar clusters in the top and middle region of the specimen, while the influences on the microstructures at the bottom are not significant. The proportion of α2 decreases with the preheating temperature,leading to a diminishing hardness. At the same time, the percentage of bulk-like γ phases increases, which results in the promotion of compressive properties. When the preheating temperature is set at 450 ℃, the fabricated specimen shows the highest compressive strength and compression ratio.