Enhanced mechanical properties of high-temperature-resistant Al-Cu cast alloy by microalloying with Mg

The effects of microalloying with Mg (0-0.23 wt%) on the microstructural evolution and mechanical properties of Al-Cu 224 cast alloys at ambient and elevated temperatures are investigated using transmission electron microscopy, differential scanning calorimetry, and tensile/compression testing. The results show that microalloying with Mg significantly enhances the precipitation of the theta' phase during aging, producing fine, dense, and uniformly distributed theta' precipitates. These precipitates are much more effective for alloy strengthening than are the theta '' precipitates in the alloy without Mg. During stabilization at 300 degrees C for 100 h, the dominant process becomes coarsening of the theta' phase. The Mg-containing alloys have much finer and denser theta' precipitates and thus considerably higher yield strengths at elevated temperature as compared to those of the alloy without Mg. The improvement is more pronounced at low Mg contents (0.09%-0.13%) than at high contents. The yield strength at 300 degrees C of the 0.13% Mg alloy is as high as 140 MPa, which is far superior to that of most cast aluminum alloys. Moreover, the enhanced yield strength of this alloy is well preserved during prolonged exposure at 300 degrees C for 1000 h, indicating that it is a promising lightweight material for high-temperature applications. (C) 2020 Elsevier B.V. All rights reserved.