Enhancement of high temperature strength of Al-Cu alloys by minor alloying and hot working process

The paper reports the design and development of wrought Al-Cu alloys that retain high strength until 250 degrees C. It is achieved by minor alloying of Zr (< 0.15 at%) and Nb (< 0.1 at%) and inducing precipitation of stable nanometric dispersion of L12 ordered precipitates during controlled thermomechanical treatment (rolling) of cast alloys before conventional heat treatment (solutionizing and ageing). The rolling tem-perature was optimized to 450 degrees C by quantitatively evaluating the size distribution of the dispersions at different rolling temperatures. The dispersions influence the microstructure and the nature of the pre-cipitation of the strengthening theta' plates during subsequent conventional heat treatment. The microstructure of the processed alloy show stability at high temperatures. The atom probe tomography reveals Zr en-richment at the broad faces of theta' plates. The presence of Zr plays a critical role in the high-temperature strength by promoting the stability of theta' precipitates and resisting its coarsening. The composite micro-structure of Al-Cu-Nb-Zr alloy displayed yield strength (YS) of 415 MPa and 220 MPa at room temperature and at 250 degrees C, which are higher by 26 % and 45 % respectively as compared to a commercial Al-Cu based alloy (2219-T851). The present results are promising for developing wrought Al alloys for high-temperature applications. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

The paper presents the design and development of wrought Al-Cu alloys with high strength retention at high temperatures. By introducing small amounts of Zr and Nb and inducing the precipitation of stable nanometric dispersion, the alloys exhibit excellent stability and high strength. The study provides promising results for the development of Al alloys for high-temperature applications.