Atomic hysteretic diffusion enables high-strength TiAl/Ni joints via cluster-plus-glue-atom modeled GCFMs

The development of high-performance Ni/TiAl composite structures demands innovative solutions to overcome strength-ductility synergy. This work introduces a gradient-driven atomic hysteretic diffusion strategy to achieve TiAl substrate-matching mechanical performance. By combining [Ni-Ni3Ti9]Ni3 and [B-Ni9]B3Ni2 cluster-plus-glue-atom modeled gradient composite filler metals (GCFMs) (Ni54Cr19B19Si8/Zr25Ti25Ta6.25Ni25Cu18.75), we established spatiotemporal control of solid-liquid interfaces at the zone I/II interface and zone III/IV interface, inducing atomic diffusion hysteresis that converted brittle Ti-based intermetallic compounds (IMCs) into gradient-distributed Ni-based solid solutions in zones II and III. The resultant architecture of TiAl/K4169 brazed seam combined dispersion strengthening via CrB4 in zones I and II, solid solution strengthening from lattice distortion in zones II and III, and the covalent interface (Ta-mediated Wad increased 8.23%) in zone IV. The optimized K4169/TiAl brazed joint exhibited exceptional shear strength (479 MPa, comparable to that of the TiAl substrate) through synergistic mechanisms: crack bridging via 95% high-angle grain boundaries (HAGBs), stress redistribution through reticulated Niss(Cr,Fe), Niss(Zr,Si) and Niss(Al,Ti) networks, and interfacial covalent bond reinforcement. This GCFM strategy provides a generalized framework for joining dissimilar metals, demonstrating 40% strength enhancement over conventional brazed joints while enabling damage-tolerant composite architectures for aerospace applications.