High-temperature properties and microstructural evolution of Al–Cu–Mn-RE (La/Ce) alloy designed through thermodynamic calculation

Abstract

A theory guide method based on thermodynamic calculation and experimental verification is performed on the composition optimization and heat treatment process of heat-resistant Al–Cu–Mn-RE(La/Ce) alloys. Al-5.0Cu-0.6Mn-1.5RE(La/Ce) is obtained to be the reasonable alloy composition for further investigation. The strength of heat treatment state alloy decreases 20–33 MPa as the temperature rises every 50 °C in the high temperature tensile experiments. The alloy has good heat resistance, with high temperature (300 °C) strength of 102.4 MPa. The high temperature fracture mode is a mixed forms of brittle and ductile fracture. Heat exposure temperature has a significant effect on both thermal and electrical conductivity, by influencing the morphology and distribution of heat-resistant phases. With the increase of heat exposure temperature, the tensile strength of the alloy firstly increases and then decreases. With heat exposure at 200 °C or 350 °C for 100 h, the room temperature tensile strength values are 232.77 MPa or 190.52 MPa, respectively, which indicates that the alloy has good high-temperature durable performance. The nano-sized Al2Cu phase, T phase and Al3Zr phase exist in the heat treatment state alloy, and result in good heat resistance. Heat exposure at 300 °C for 100 h leads to the growth of Al2Cu phase and close distribution of heat-resistant phase Al3Zr around the Al2Cu phase. Presence of eutectic phase hinders the dislocation movement and thus improves the resistance to deformation at high temperature.