<p>With the rapid development of aerospace, transportation, and other fields, the research on heat-resistant aluminum alloys has attracted increasing attention. In this work, Al–Cu alloys with the addition of TiB₂ and Er were prepared by a melt reaction method. The influence of in-situ TiB₂ particles and micro-alloying element Er on the microstructures as well as the properties of Al–Cu alloy was investigated. The results demonstrate that the in-situ TiB₂ particles not only significantly refine the grain size, modify the Al₂Cu minority phase, but also promote the increase in the tensile properties and elastic modulus at room temperature and high temperature. The addition of rare earth Er can further improve the tensile properties and elastic modulus of Al–Cu alloy with in-situ TiB₂ particles. The effect mechanism of in-situ TiB₂ particles and micro-alloying element Er has also been explored. This work provides a strategy for concurrently improving the tensile performances and elastic modulus of aluminum alloy at room temperature and high temperature.</p>