Experimental and modeling investigations of the non-isothermal and isothermal precipitations in an Al-Cu-Mg-Zr alloy with various pre-precipitation microstructures

Abstract

The complex precipitation evolutions of Al-Cu-Mg alloys during both non-isothermal and isothermal thermal processes have been found to work on their mechanical properties and electrical resistivity. Modeling of the precipitation kinetics, electrical resistivity and strength evolution is therefore essential for optimizing heat treatment and processing of these alloys. In this work, in situ electrical resistivity monitoring during both non-isothermal and isothermal thermal processes and microstructural characterizations were conducted on an Al-Cu-Mg-Zr alloy with different pre-precipitation microstructures to provide fundamental insights of precipitation behaviors. The results showed that precipitation behaviors of Al-Cu-Mg-Zr alloy, such as the dominant strengthening phase, were highly dependent on pre-precipitation microstructures and thermal history. A time–temperature-microstructure-properties map was established to unravel precipitation characteristics and their strengthening functions. The maximum hardness was indicated to be attributed to the combined presence of Guinier–Preston–Bagaryatsky (GPB) zones and fine S (Al2CuMg) phase. Further, in situ electrical resistivity was used as the main input data to develop an improved model based on the classical Kampmann and Wagner type numerical model (KWN model). This integrated model could not only reveal precipitation kinetics but also well predict hardness evolutions of the studied alloy during non-isothermal and isothermal processes.

Keywords

• Al-Cu-Mg alloy
• Precipitation
• Heat treatment
• In situ electrical resistivity
• Strengthening