Work

Microstructural characteristics of 7449 aluminum alloy in rolling and isothermal treatment conditions

Year: 2026

Type: article

Abstract: The direct isothermal treatment methodology was predominantly intended to materialize the preparation of semi-solid billets (SSB). For hot-rolled 7449 aluminum alloy (7449 AA), a comparison was conducted to dig into how isothermal temperature and holding time impact microstructure evolution and coarsening rate. The results showed that heating the alloy at 610 ℃ for 20 min transformed its initial lath-shaped grains and low-angle grain boundaries (LAGBs) into nearly spherical equiaxed grains and high-angle grain boundaries (HAGBs), and the microstructure shifted from preferred to random orientation. Post-isothermal treatment, the alloy’s texture changed from a deformation-recrystallization mixture to a recrystallization-dominated one. Rising temperature converted deformed grains to recrystallized ones and reduced texture intensity gradually. Average grain size and shape factor both increased with higher temperatures and longer holding times. Heating at 595 ℃ for 20 min caused insoluble precipitates and fine second phases to dissolve into the α-Al matrix, with the loss of grain boundary (GB) pinning effects, the grains underwent coarsening. At GBs, a substantial Cu-rich liquid phase formed accordingly, while fine within-grain dot-like Cu-rich liquid phases dispersively formed unevenly. Concurrently, MgZn2 precipitates were formed and dispersively distributed throughout the 7449 AA. An excessively high holding temperature can induce the formation of dendrites at GBs, and the number of dendrites increases gradually with the prolongation of holding time. Grain growth and spheroidization were governed by the combined mechanism of coarsening and Ostwald ripening.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2026.03.142

Authors: Yan Chen, Jufu Jiang, Lingbo Kong, Fuguan Cong, Honglei Liu, Ying Wang

Institution: Harbin Institute of Technology

Language: English

Topic: Aluminum Alloy Microstructure Properties

Subfield: Aerospace Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,640

Funders: National Natural Science Foundation of China, National Science and Technology Major Project