Superior shear strength subject to the regulation of plastic toughness in K4169 alloy/TiAl intermetallic joints vacuum brazed with gradient composite amorphous filler metals

• Published in: Composites. Part B, Engineering Vol. 274; p. 111288
• Main Authors: Zhang, Liangliang, Li, Peng, Li, Shuai, Nie, Fuheng, Wu, Baosheng, Li, Chao, Li, Jiachen, Zhang, Zhenyang, Jiang, Xin, Zhao, Bomin, Dong, Honggang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2024
• Subjects: Gradient composite amorphous filler metal; HAGBs; K4169/TiAl brazed joints; Lattice distortion; Plastic toughness; Gradient composite amorphous filler metal; HAGBs; Lattice distortion; Plastic toughness; K4169/TiAl brazed joints
• ISSN: 1359-8368; 1879-1069
• DOI: 10.1016/j.compositesb.2024.111288

The concept of gradient composite amorphous filler metal (GAFM) was utilized to solve the scientific problem of low strength caused by excessive Ti-containing brittle-hard intermetallic compounds (IMCs) generated in Ni/TiAl brazed joints through interfacial hysteresis reaction. Based on the cluster-plus-glue-atom model, the GAFMs (Zr25Ti21.25Ni25Cu18.75/Zr31.25-XVXCu50Ni18.75) were designed for vacuum brazing of K4169 alloy with TiAl intermetallic. And the shear strength of the joint brazed with (Ti21.25Zr25Ni25Cu18.75/Zr25V6.25Cu50Ni18.75) GAFM reached 344 MPa. The relation between grain boundary, solution, dislocation and strength was established. The cracks initiated from the (Ti,Zr)(Ni,Cu)+(Cr,Fe,Ni) brittle-hard phase and the plastic-tough phase (Zr,Ti)(Ni,Cu) interface in Zone II with (Ti21.25Zr25Ni25Cu18.75/Zr31.25-XVXCu50Ni18.75) GAFMs at 1040 °C/10 min, and then extended to the (Ti,Zr)(Al,Ni,Cu)3[010]/(Ti,Zr)(Ni,Cu,Al)3[0-10] non-coherent interface. To regulate the distribution of the plastic-tough phase in Zone II, raising brazing temperature could promote the dissolution of Zone I into Zone II. The addition of V to the GAFMs, εG and εα mismatches increased and prompted the Niss[00-1]+TiAl[010] phase, (Cr,Fe,Ni)ss[00-1] phase with a-value lattice distortion of 21.38%, (Ni,Cr,Fe) and ZrNi3[0-2-1] grains refinement in Zone II, where KIC*/KIC>1, the brazed joint strengthening effect was enhanced. The columnar grains were transformed into grains with reticulated cladding characteristics. The percentage of substructured grains increased from 46.6% to 56.3%, and the percentage of HAGBs rose to 84.7%, which inhibited dislocation migration. Therefore, the ZrNi3 plastic-tough phase, prohibited the expansion of the major crack generated from the (Cr,Fe,Ni) brittle-hard phase. The major crack extended to the Ti(Ni,Cu,Al)3 [1–10]/Ti(Al,Cu,Ni)2[0-10] semi-coherent interface and then to the TiAl substrate, resulting in a zigzag crack expansion. [Display omitted] •Novel Zr25Ti21.25Ni25Cu18.75/Zr31.25-XVXCu50Ni18.75 GAFMs were designed.•Analyzed the strengthening mechanism of the TiAl/K4169 joint as strong as 344 MPa.•Regulated the microzone plastic toughness of the brazing seam.•Established the relation between grain boundary, solution, dislocation and strength.