High-Temperature Mechanical Properties of Aluminum Alloy Matrix Composites Reinforced with Zr and Ni Trialumnides Synthesized by In Situ Reaction

Abstract

High-temperature strengths and stabilities of Al3Ni and Al3Zr phases can be used to develop heat-resistant Al-matrix composites. In the current study, Al-1Mg-0.8Mn-0.8V alloy matrix composites are synthesized by in-situ reaction of K2ZrF6 salt and Ni powder to yield Al3Zr- and Al3Ni-reinforcing phases. The as-cast microstructural and room-temperature and high-temperature tensile properties of the composite are investigated. The microstructure of the composites contain α-Al, Al3Zr, Al3Ni, and Al10V phases. The eutectic mixture comprises alternating Al3Ni and α-Al phases with fine Al3Zr precipitates distributed in the interlamellar regions. The (2 pct Al3Zr + 15.2 pct Al3Ni)/Al-alloy composite shows the highest mechanical properties at room temperature, with a tensile strength of 198 MPa and a fracture strain of 6.55 pct. At 200 and 300 °C, tensile strengths of (2 pct Al3Zr + 13.3 pct Al3Ni)/Al-alloy and (2 pct Al3Zr + 15.2 pct Al3Ni)/Al-alloy composites reach 175 MPa and 166 MPa, and 191 MPa and 155 MPa, respectively. At 350 °C, the highest tensile strength of this composite family reaches 82 MPa, which surpasses some of the existing Al-Si alloys used in automotive pistons, suggesting its potential high-temperature applications. Analysis indicates that the fracture mode of the present composites is ductile. Transgranular cleavage fracture of coarse, brittle Al10V phase, and microvoid coalescence are the main failure mechanisms.