冷轧对CT20钛合金微观组织和力学性能的影响

Effect of cold rolling on microstructure and mechanical properties of CT20 titanium alloy

选取通过轧制工艺制备的四种不同厚度的CT20钛合金板材,采用多种技术对其微观组织进行表征,测试板材的硬度以及沿轧件的轧制方向(RD)和横向方向(TD)拉伸的力学性能,分析微观组织与力学性能之间的内在联系。结果表明:在冷轧过程中,高密度的位错触发了合金的非晶化转变,变形量的增大使α相沿RD伸长,β相和βt组织破碎。位错和亚结构数量的提高不仅使合金硬度上升,而且使RD和TD的拉伸强度增大,伸长率下降。RD的断裂类型属于韧性断裂,TD的断裂类型属于韧脆混合型断裂。在冷轧过程中,基面滑移和柱面滑移共同参与织构的演变,由此形成的织构取向对板材RD和TD两方向的滑移行为和力学性能产生了重要影响;同时,由于位错在RD和TD两方向上的滑移距离不同导致不同的加工硬化阶段。

CT20 titanium alloy sheets with different thicknesses prepared by the rolling process were studied.Various techniques were used to characterize the microstructure,hardness and mechanical properties of the sheets in rolling direction(RD)and transverse direction(TD),and the intrinsic connection between microstructure and mechanical properties was analyzed.The results show that the high density of dislocations triggers the crystalline-to-amorphous transition during cold rolling.The increasing rolling reduction makesαphase elongate along RD,βphase andβt structure break severely.Massive dislocations and substructures introduced by cold rolling enhance the alloy hardness,raise the tensile strength and drop the elongation in RD and TD.The fracture type in RD is a ductile fracture,and that in TD is a mixed tough-brittle fracture.During the cold rolling process,the basal slip and prismatic slip are jointly involved in the evolution of the texture,and the resulting texture orientation has an essential influence on the slip behavior and mechanical properties of the sheets in RD and TD,while the different slip distances of dislocations in RD and TD lead to different work-hardening stages.