Revisiting the stability, mechanical, and thermal properties of Au–Ni brazing filler metal alloys at finite temperatures via first-principles calculations

Abstract

Au0.825Ni0.175 filler metals are widely utilized in aerospace and military applications due to their high melting point and excellent corrosion resistance. However, its low strength and high cost limit broader adoption. Therefore, first-principles calculations were employed to evaluate the thermophysical properties and strength of Au–Ni alloys. Analysis of the unfolded partial phonon spectrum at 0 K revealed a transition in dominant chemical bonding from Au–Au to Ni–Ni with increasing Ni content. The composition-temperature-dependent models for thermal expansion, elastic modulus, stacking fault energy, and compressive strength were constructed. The results indicated that Ni addition enhanced the compressive strength of Au–Ni alloys but reduced their ductility. The thermal expansion coefficients of Au–Ni alloys were found to be highly compatible with those of Ni-based alloys. Selection of temperature ranges with practical applications, strength, ductility, and thermal expansion were optimized, identifying Au0.73Ni0.27, Au0.75Ni0.25, and Au0.74Ni0.26 as promising compositions for 600, 800, and 1000 K, respectively. Compared to Au0.825Ni0.175, these alloys exhibited 9.25%–20.20% higher compressive strength. This work provides valuable insights into the Au–Ni alloys for high-performance applications.