Quantitative effects of pre-deformation prior to non-isothermal aging on the mechanical properties-microstructure relationships in an Al-3.51Cu-1.01Li alloy

Abstract

The effects of increasing levels of pre-deformation on the mechanical properties and microstructure evolution (dominantly T1 phase) of an extensively used aerospace Al-Cu-Li alloy have been systematically investigated during the non-isothermal aging. Quantitative descriptions extracted from the microstructure parameters further revealed the separated strengthening contributions and mechanism. Pre-deformation prior to the NIA significantly accelerated the aging kinetics and improved the strength, and yet showed a limited benefit due to the generally decreased precipitation strengthening. Elevated pre-deformation in conjunction with the NIA process reduced the T1 diameter and interprecipitate spacing, the interprecipitate diffusion was gradually activated, responsible for the undulatory mean thickness. The experimental yield strength was successfully described by invoking the shearing mechanism in the pre-deformed samples (4–20 %). However, the strengthening transition from shearing to by-passing occurred in the 0 % sample, the by-passing model should be considered simultaneously owing to the larger diameter T1 precipitates. The critical diameter of the T1 precipitate for this transition ranged from 84 to 117 nm and was approximately 100 nm.

Keywords

• Al-Cu-Li alloys
• Pre-deformation
• Non-isothermal aging
• Precipitation strengthening
• Strengthening mechanism