The Ti/TiAl/Al system functionally graded material was fabricated with two-step brazing method. Firstly, the vacuum brazing of TC4 to TiAl was carried out using Ti-Zr-Cu-Ni-Co brazing filler at 960℃ for 10min. Secondly, with pure-metal powder of Al-25Cu-5Si, the joint of TiAl/LF21 was brazed at 590℃ for 10min. As a consequence, a thin diffusion layer near TiAl base metal was formed in TC4/TiAl joint. In particular, the transient phases of Ti3Al and Ti2Al were found to be formed within the 50μm-thickness brazing seam in the TC4/TiAl joint. The density of TC4/TiAl/LF21 FGM changes quasi-continuously from 4.5g/cm3 to 3.8g/cm3 and to 2.7g/cm3 in its thickness direction.%采用两步钎焊方法来完成梯度材料的制备:第一步,选用Ti-Zr-Cu-Ni-Co急冷态箔带钎料钎焊TC4/TiAl接头,钎焊规范选为960℃/10min;第二步,采用高纯度的Al,Cu和Si粉末混合配制Al-25Cu-5Si钎料,用于钎焊TiAl/LF21接头,钎焊规范选为590℃/10min.结果表明,两步钎焊法成功实现了TC4/TiAl/LF21这种轻质变密度梯度材料的制备,其中在TC4/TiAl的50μm钎缝宽度范围内,近似出现了Ti3Al和Ti2Al过渡相.获得的TC4/TiAl/LF21梯度材料密度沿厚度方向由4.5g/cm3下降至3.8g/cm3,之后再下降至2.7g/cm3,呈现较为平缓的准连续变化趋势,有效避免了材料在局部界面的密度值突变.
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