材料期刊网

钛合金筒形件具有轻质、 高强、 耐腐蚀等优点,在航空、 航天和兵器领域有着广泛的应用与需求.针对目前的钛合金筒形件成形制造工艺难以满足大直径薄壁长筒形件的高效、 低成本制造要求,提出了一种环轧-旋压(轧-旋)成形工艺制造钛合金筒形件的方法.在轧-旋成形工艺中,坯料历经环轧线接触与旋压点接触下的连续局部加载增量成形和显著的不均匀变形,其变形过程复杂,微观组织不均匀,容易发生破裂,影响筒形件的成形质量.为此,基于两相钛合金自洽模型和Oyane韧性准则,建立了耦合损伤的轧-旋宏微观仿真模型,研究了TA15钛合金筒形件轧-旋过程中的宏观变形行为、 微观组织和损伤破裂演化规律.发现工件经轧-旋成形后,外层应变较大,中间层和内层基本相同;工件温度沿壁厚由内到外逐渐降低;α晶粒尺寸外层最小,内层和中间层相差不大;α相体积分数沿壁厚由内到外逐渐降低;工件内表面在环轧后的旋压过程中,由于正应力三轴度以及高应变速率的共同作用,最易发生破裂.

Due to the characteristics of light weight, high strength and good corrosion resistance, titanium tubes have been widely applied and needed in the fields of aviation, aerospace and weapon. Considering that the existing processes are difficult to manufacture long, thin?walled titanium tubes with large diameter in efficiency and at low cost, a new tube form?ing technique by combining ring?rolling and tube spinning ( called rolling?spinning) is developed. In the rolling?spinning process, blanks experience continuous local loading forming under the line contact action in ring?rolling process and point contact action in tube spinning process. These forming characteristics would lead to complex deformation history, inhomo?geneous microstructure and fracture, which would finally affect the performance of tubes. Therefore, based on the two?phase self?consistent model and Oyane criterion, a macro?micro finite element model coupling the damage effects is estab?lished. Using this model, the macro deformation behaviors, microstructure and damage evolutions are investigated. The re?sults indicate that after the rolling?spinning process, the strain and α grain size are largest in the outer zone of the work?piece, while the strain and α grain size are almost same in the inner and center zones of the workpiece; the temperature and volume fraction of α phase decrease along from the outer surface to inner surface of the workpiece;the fracture would occur in the inner surface of workpiece during the spinning process due to the coupling effects of positive stress triaxiality and high strain rate.