Continuous Heating Aging Characteristics of Al-Cu-Mg-Ag Alloy Based on Stress Relaxation Method

Abstract

Clarifying the aging characteristics of aluminum alloys during continuous heating is crucial for formulating isothermal and non-isothermal aging (continuous heating aging) processes. This paper investigates the stress relaxation characteristics of an Al-Cu-Mg-Ag alloy under three-point bending during continuous heating. Taking into account the mechanical properties and precipitate analysis, it demonstrates the feasibility of using the stress relaxation method to determine the peak aging temperature during continuous heating. This approach is efficient, requires minimal sample, and yields continuous data. The peak aging temperature of the sample increases from 260 °C to 305 °C when the heating rate increases from 1 to 3°C/min with the same initial load (3 N). The peak aging temperature is around 280 °C, when the initial load increases from 1 N to 9 N with the same heating rate (2 °C/min). Under low temperatures (25 °C~ 200 °C), the sample displays the presence of GP I zone, GP II zone, and a few Ω precipitates during the continuous heating process of 2 °C/min. As the temperature increases, the GP II region dissolves and transforms into the Ω precipitates. A large number of Ω precipitates appear in the matrix in a continuous precipitation manner when the temperature reaches 235 °C. The precipitation strengthening effect is strongest at 280 °C, and the Ω precipitates begin to coarsen as the temperature exceeds 280 °C.

Keywords: Al-Cu-Mg-Ag alloy, continuous heating, stress relaxation method, precipitates