| As the lightest magnesium alloy,Mg-Li alloys have attracted increasingly attention in recent years due to their potential applications as the lightweight structural materials.In the present work,the microstructure and texture evo lution of a single-phased Mg-4.5Li extruded plate with a HCP structure and a dual-phased Mg-8Li extruded plate with HCP and BCC structure rolled along the transverse direction(TD)and extrusion direction(ED)was systematically studied.The mechanisms of microstructure and texture evolution were investigated using XRD,EBSD,optical microscropy.The main findinds are summarized as follows:(1)For the Mg-4.5Li alloy,deformation microstructure is not sensitive to strain path.Namely,there is little difference in microstructure rolled along different directions and the microstructures of both rolled plates are consisted of a high fraction twins;However,the deformation texture shows a rolling path dependence:the double-peaked texture with basal pole tilting±20~o from ND to RD is presented in both rolling paths,but a weak texture component with double-peaks of(0002)poles from ND to TD appear in the plate rolled along the ED.Meanwhile,the maximum texture intensity is only 5.7for ED-rolling,but 9.8 for TD-rolling.(2)The annealing texture of Mg-4.5Li TD-rolled plate is different that of ED-rolled one:the(0002)poles in ED-rolled plate show a dispersion distribution within range of 30~o circumference away from the ND,while those are concentrated near the ND in the TD-rolled plate.The maximum pole density of the ED-rolled sample is obviously weaker than that of the TD-rolled sample.The basal poles tilted from ND to TD of some recrystallization grains after annealing in the ED-rolled sample mainly account for the differences in the annealing texture.(3)For the duplex phase Mg-8Li alloy,both the microstructure and the texture ofα-Mg phase are highly dependent on the rolling path:the deformation microstructure in the ED-rolled sample shows a large number of elongated lamellar microstructure and a small number of blocked microstructure.The rolled microstructure in the TD-rolled sample is mainly composed of blocked microstructure.The texture in the ED-rolled sample is a two peak basal texture with c aixis tilting±60~o from ND to TD and a weaker one with with basal poles tilting±20~o from ND to RD,while the texture in the TD-rolled plate is composed of only one basal component with double peaks of(0002)poles tilting±20~o from ND to RD.The differences of microstructure and texture result from the coordination of deformation mechanisms of the two phases under different rolling paths:the TD-tilting texture is derived from the lamellar structure and the RD-tilting texture is from the blocked structure.There was no rolling path dependence for the deformed texture ofβ-Li phase,and all samples showed a(001)<110>fiber texture.(4)For the annealing texture ofα-Mg phase in the Mg-8Li alloy,the RD-tilted two peaked texture component in the ED-rolled sample gradually disappeared with higher annealing temperature and a longer time,while the TD-tilted double peaked texture component is gradually approached to ND and finally transform into a weaker TD-tilted texture.The RD-tlted deformation texture of the TD-rolled sample remains after annealing. |
