摘要
经α+β两相区变形及退火后的TB6钛合金模锻件低倍组织局部区域显现出了粗晶缺陷。通过热模拟试验,结合微拉伸及扫描电镜(Scanning electron microscope,SEM)、背散射电子衍射仪(Electron black-scattered diffraction,EBSD)等微观分析手段,分析对比低倍组织中粗、细晶区的显微特点及力学性能,探讨低倍粗晶形成机理,提出低倍粗晶显现的工艺判据并建立预测模型。结果表明,低倍粗晶主要分布在变形温度低且变形程度大的金属剧烈流动区域,与细晶材料相比,粗晶使得屈服强度降低,但伸长率和抗拉强度提高。经两相区加热后,锻件转运过程中表面温度降低,温降导致表面区域温度不均,在大变形速率下,表面圆弧区域软化程度差别较大,易发生部分动态再结晶,产生晶界角较大的动态再结晶晶粒(β相)。退火后,该动态再结晶晶粒通过晶界迁移实现对周边产生的晶界角较小的静态再结晶晶粒的吞并,形成粗晶。变形温度(T)越低,变形量越大且不超过临界值时,低倍粗晶越容易显现。建立T与ε_(f)间的量化关系;以ε_(f)为判据,通过二次开发建立有限元子程序,实现锻件低倍粗晶分布的可视化预测。
The local area of macrostructure of TB6 titanium alloy die forging shows the flaw of coarse grain after deformation and annealing in two-phase region.By means of thermal modeling test,optical microscope(OM),micro-tensile tests and scanning electron microscope(SEM),electron black-scattered diffraction(EBSD),the microstructure characteristics and mechanical properties of"the area of macrostructure coarse grain"and"the area of macrostructure fine grain"are analyzed and compared,the formation mechanism of macrostructure coarse grain is discussed,the process condition criterion of the appearance of the macrostructure coarse grain is put forward and the prediction model is established.The results reveal that the macrostructure coarse grain is mainly distributed in the area of violent metal flow with low deformation temperature and large deformation degree.Compared with fine-grained materials,coarse-grained materials reduce the yield strength,but increase the elongation and tensile strength.After heating in the two-phase zone,the surface deformation temperature of the forging decreases during transportation,which leads to uneven temperature in the surface area.At large deformation rate,the softening degree of surface arc region is quite different,and partial dynamic recrystallization is easy to occur,resulting in dynamic recrystallized grains with large grain boundary angle(βphase).After annealing,the dynamic recrystallized grains merge the static recrystallized grains with small grain boundary angle around through grain boundary migration to form coarse grains.With the deformation temperature(T)decreases and the strain(ε)increases,the macrostructure coarse grains appear more easily when the strain(ε)does not exceed the critical value.The relationship between ε_(f) and T is expressed quantitatively;Taking ε_(f) as the criterion,the finite element subroutine is established through secondary development,and the visual prediction of macrostructure coarse grain of forging is realized.
作者
张禹森
陈雷
刘胜杰
胡峻华
张启飞
崔明亮
胡建良
金淼
ZHANG Yusen;CHEN Lei;LIU Shengjie;HU Junhua;ZHANG Qifei;CUI Mingliang;HU Jianliang;JIN Miao(School of Mechanical Engineering,Yanshan University,Qinhuangdao 066004;China Second Heavy Machinery Group,Deyang Wanhang Die Forging Co.,Ltd.,Deyang 618013)
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2024年第8期121-131,共11页
Journal of Mechanical Engineering
基金
国家自然科学基金资助项目(52075474,51675467)。
关键词
TB6钛合金
低倍粗晶
形成机理
再结晶
可视化模型
TB6 titanium alloy
macrostructure coarse grain
formation mechanism
recrystallization
visualisation model
