Mechanism of microstructure and properties evolution of 2195 Al-Li alloy during radial-direction hot compression and heat treatment: Determined by shape, size and rotation of grains

Abstract

Extruded bars are one of the important hot forming raw materials for Al-Li alloy. They typically exhibits strong textures and anisotropy, which significantly affect the subsequent hot deformation microstructure and properties. Thus, this study investigates the radial-direction (RD) hot compression of a 2195 Al-Li alloy extruded bar, the mechanical properties and corresponding microstructure evolution mechanisms along the axial (AD) and circumferential (CD) directions of the original bar are analyzed. The results revealed a <111>//AD texture in the original bar, with significant anisotropy observed in the T6-state (solution, quenching and artificial peak aging) bar. After compression and T6-treated, the yield and tensile strengths along the AD generally decreased, while along the CD first increased then decreased, and the strength anisotropy is significantly reduced. However, anisotropy in elongation persisted, with the elongation along the CD significantly lower than that along the AD. This is mainly attributed to the grains with high-angle grain boundaries maintained an elongated shape along the AD. In addition, smaller grain size and higher HAGB proportion result in lower elongation along the CD. The change in yield strength showed a notable positive correlation with the peak intensity of the texture near <111>. A grain rotation model that determines the evolution of texture was established. During compression, the <111>//AD grains firstly rotate around the AD to reach the <110>//RD, then alternately and cyclically slip on two different {111} planes as the Schmidt factor changes, ultimately causing the grains to rotate around the RD.