A high-strength, heat-resistant Al–5.7Ni eutectic alloy with a Zr–induced bimodal grain structure fabricated by laser powder bed fusion

Abstract

Eutectic Al–Ni alloys are attractive for laser powder bed fusion (LPBF) because their narrow solidification range reduces susceptibility to solidification cracking. In this study, a high-strength, heat-resistant Al–Ni–Zr alloy was fabricated by LPBF using blended Al–5.7Ni and ZrH2 powders. The composition of the as-built sample is Al–5.72Ni–0.89Zr (wt.%). The alloy exhibited a nanoscale cellular eutectic structure consisting of α-Al cell interiors and Al3Ni-rich cell walls, together with fine equiaxed grains near the melt-pool boundaries and elongated columnar grains within the melt-pool interiors. At room temperature, the alloy achieved a yield strength of 352 MPa, an ultimate tensile strength of 520 MPa and a fracture elongation of 6.5%. At 300 °C, it retained a yield strength of 165 MPa and an ultimate tensile strength of 188 MPa. The high room-temperature strength is associated with the fine Al3Ni-containing cellular eutectic network, whose largely retained morphology after short-term exposure at 300 °C may also contribute to the elevated-temperature strength. The findings of this study will provide valuable insights for the development of more high-performance LPBF-prepared eutectic aluminum alloys.