Enhancement of Elevated‐Temperature Strength in Al–Cu–Ce–Mn–Zr Cast Aluminum Alloy Through Ni Alloying

Herein, to enhance the elevated‐temperature strength of heat‐resistant aluminum alloys to satisfy application requirements, the effect of Ni content (0.5, 1.0, 2.0, 4.0 wt%) on the microstructures and tensile properties of Al–8.4Cu–2.3Ce–1.0Mn–0.2Zr alloy is investigated. The metallographic analysis techniques are used to quantitatively examine the microstructural changes. The skeleton‐like Al₇Cu₄Ni phase is formed after the addition of Ni and its morphology is gradually transformed into a coarse reticular‐like shape with Ni content increasing. However, the thermally stable Al₈CeCu₄ and Al₂₄MnCu₈Ce₃ phases disappear when Ni content exceeds 1.0%. Al–8.4Cu–2.3Ce–1.0Mn–0.2Zr–0.5Ni alloy exhibits the optimal elevated‐temperature tensile performance at 400 °C, and its ultimate tensile strength, yield strength, and elongation at 400 °C reach 105, 85 MPa, and 16.5%, respectively. The optimal tensile performance is attributed to synergistic enhancing action of the thermostable Al₈CeCu₄, Al₂₄MnCu₈Ce₃, Al₁₆Cu₄Mn₂Ce, and Al₇Cu₄Ni phases at the grain boundaries and the nano‐sized Al₂₀Cu₂Mn₃ and Al₂Cu precipitates inside the grains. The typical brittle fracture is dominating in the five alloys with different Ni contents at ambient temperature, but the fracture mode at 400 °C is changed from ductile fracture to ductile and brittle mixed fracture with the increase of Ni.