Effect of pre-aging on creep aging properties and microstructure evolution of 2195 Al–Li alloy

Abstract

Creep aging forming (CAF) is a potential process to manufacture large integral components of Al–Li alloys, which exhibits poor formability and susceptibility to damage and cracking via traditional plastic forming processes. Al–Li alloys also have disadvantages, such as low creep and comprehensive properties.To address this problem, this study adopted pre-aging as a treatment process before creep aging (CA). The effects of pre-aging at different temperatures (65 °C, 90 °C, and 115 °C) on the CA of Al–Li alloys were evaluated at 155 °C for 18 h. Creep strain, the evolution of mechanical properties, and the microstructural characteristics were investigated as well. The results showed that pre-aging could effectively influence the subsequent CA behavior. As the pre-aging temperature increased, creep strain accumulation during CA decreased. Meanwhile, pre-aging significantly increased the elongation (EL) of the specimens after CA; Notably, the increase in EL did not compromise strength. Changes in the microstructure of the specimens after pre-aging and CA tests were observed by transmission electron microscopy. The effect of pre-aging on the subsequent CA properties mainly revealed that the strength was not lower than that of the specimen without pre-aging after the same CA test through adjusting the percentage and size of the T1 and θ′ phases. In addition, pre-aging could promote the transformation of the fracture mechanism from intergranular fracture to mixed fracture in the specimen after CA.

Keywords

• Al–Li alloy
• Pre-aging
• Creep aging
• Mechanical properties
• Microstructure evolutions