Effect of Rolling and Artificial Aging Treatment on the Microstructure and Mechanical Properties of a 2195 Al–Li Alloy by Ultrasonic Casting

Synergistic strengthening by plastic deformation and heat treatment is an important way to correct the casting defects of 2195 Al‒Li alloys and enhance their strength and plasticity. In this study, homogenized 2195 Al‒Li alloy ingots were hot-rolled at 450 °C and cold-rolled at 25 °C. The deformed samples were heat treated at T6. The effects of cold rolling and hot rolling processes on the microstructure and mechanical properties of 2195 Al‒Li alloys were compared. The strengthening behaviors of the two rolled state 2195 Al‒Li alloys under different aging regimes were explored. The experimental results revealed that the aging hardening effect was more distinct at 180 °C, and cold rolling produced better mechanical properties than hot rolling did. The samples cold-rolled at 180 °C for 18 h presented a tensile strength, yield strength, and elongation of 515.4 MPa, 439.3 MPa, and 11.0%, respectively. Under the cold rolling process, the grain refinement effect is more significant, the dislocation density at the grain boundaries is greater, and the role of fine-grain strengthening is more significant. After cold rolling and artificial aging, a large number of smaller and uniformly distributed T1 strengthening phases precipitated, enhancing the pinning effect on the grains and proving that the main reason for its aging strengthening effect was not fine crystal strengthening but rather precipitation strengthening.

Graphical Abstract

The study delves into the variations in mechanical properties and the formation mechanisms of plastic deformation during the rolling process of 2195 aluminum–lithium alloy. It compares the effects of cold rolling and hot rolling processes on the macroscopic and microscopic structures of the alloy. Additionally, experimental research is conducted on the aging behavior of the alloy in the rolled state. The results reveal the effects of two processes: hot rolling at 450 °C and cold rolling at room temperature (25 °C), as well as artificial aging treatments at 120, 150, 180, and 210 °C, on the mechanical properties of ultrasonically cast 2195 aluminum–lithium alloy. The results showed that for the hot rolling 18 ℃/18 h specimen, the tensile strength was 506.0 MPa, the yield strength was 395.2 MPa, and the elongation was 13.7%. Similarly, for the cold rolling 180 ℃/18 h specimen, the tensile strength was 515.4 MPa, the yield strength was 439.3 MPa, and the elongation was 11.0%. Compared with the hot rolling process, the cold rolling process had a more obvious effect on the cold rolling process, the average grain size of 2195 Al‒Li alloy was 125.7 μm, and the average grain size of the hot rolling specimens was 178.6 μm. In summary, the low-temperature cold rolling of 2195 Al‒Li alloy using a 180 ℃/18 h aging process yielded the best overall mechanical properties.