摘要
TA19钛合金具有中等强度、良好的热稳定性、抗蠕变性等特点,在先进发动机和飞行器中应用广泛。目前对TA19钛合金热处理工艺-组织-性能三者的关系研究较为系统,缺少实际锻造过程中组织及织构的直观观察和分析研究。本文使用工业级TA19钛合金铸锭在20 MN快锻机上通过共16火次的镦拔锻造制备了Φ260 mm规格的成品棒材,并使用扫描电镜(SEM)和电子背散射衍射(EBSD)技术对锻造关键火次后棒坯心部、D/4(D为直径,D/4为心部与表面的中间位置)及表面位置的α相和β相的微观组织及取向特征进行系统的表征和分析。结果表明:单相区锻造后,在原始β相内部形成多个集束状α相晶簇,取向以<0001>织构为主;当锻造结束的实际温度低于相变点时,晶簇中片层α相参与变形,并发生一定程度的碎化,偏离原有晶簇取向。在两相区锻造时,α相和残余β相都会参与变形;随着锻造火次增多,片层α相不断减小、发生等轴化,并由相变产生新的等轴α相。通过9火次两相区的锻造,各位置片层α相的平均晶粒尺寸减小程度不同,由心部至表层分别减少了12.8%,17.2%和28.2%;其等轴化程度逐渐接近,从心部至表面的长宽比分别为1.89,1.83和1.73。随着两相区锻造火次增多,α相<0001>相变织构逐渐减弱并逐渐向<1010>及<1120>形变织构偏转,但整体较弱。本文的研究目的是系统深入地分析TA19钛合金锻造过程中α相和β相的组织及织构演变规律,为棒材制备工艺优化提供理论支持。
Titanium alloy offers high specific strength,fatigue resistance,and corrosion resistance,making it widely applicable in aviation,aerospace,weaponry,petroleum,and the chemical industry.TA19 titanium alloy,also known as Ti-6242S,features medium strength,good thermal stability,and creep resistance,is widely used in advanced engines and aircraft.As we all know,titanium alloy forgings mainly adjust the proportion and size ofαphase andβphase through hot deformation and heat treatment to meet application needs.Currently,the relationship between the heat treatment process,structure,and properties of TA19 titanium alloy is relatively well understood.It is generally believed that as the solid solution temperature increases,the content of the primaryαphase decreases,while the strength and high-temperature creep properties increase.For the thermal deformation process of TA19 titanium alloy,the influence of individual deformation process parameters such as deformation temperature and strain rate on the evolution of structure and orientation is primarily studied through thermal simulation experiments.Therefore,there is a lack of intuitive observation and analytical research on the structure and texture during multi-fire forging.This article used a TA19 titanium alloy ingot with a diameter of 600 mm and a weight of 3 ton on a 20 MN fast forging machine to prepare a finished bar with a diameter of 260 mm through a total of 16 forging passes,with an up setting amount of 45%for each pass.Among them,in the 1st to 3rd passes,the bar blank was upset and stretched at 1150,1100,and 1050℃,respectively,and was air cooled after forging;in the 4th and 5th passes,it was upset and stretched at Tg-35~40℃(Tg is transformation temperature ofβ→α),while the Tp is 1004℃,and was air cooled after forging;in the 6th pass,it was upset and stretched at Tg+50℃,and water cooled after forging;In the 7th to 15th passes,it was upset and stretched at Tg-35℃,and air cooled after forging;in the 16th pass,it was upset and rounded at Tg→40℃,and air cooled after forging.Samples were taken from the center,mid-radius,and surface positions on the cross section of the bar blank after the 5th,6th,9th,12th,and 15th pass forging.Scanning electron microscopy(SEM)and electron backscattered diffraction(EBSD)techniques were used to systematically analyze the microstructure and orientation characteristics of theαphase andβphase.The texture and orientation characterization were performed using an Ultra 55 field emission scanning electron microscope(FE-SEM)equipped with an EBSD probe.The texture analysis was conducted using Channel 5 orientation analysis software.The research results showed that although varying degrees of variant selection occurred after theβ→αtransformation,resulting in transformation textures,the repeated upsetting and stretching during the forging of TA19 titanium alloy bar prevented the formation of strongαphase transformation and deformation textures.After forging inβregion,multiple clusters ofαphase clusters were formed within the originalβphase,with the orientation ofαphase clusters predominantly in the<0001>direction,perpendicular to the length of the bar blank.When the actual temperature at the end of forging was higher than Tg,the lamellarαphases in the cluster did not participates in deformation.When the actual temperature at the end of forging was lower than the T_(g),lamellarαphases would undergo a certain degree of fragmentation and deviate from the original orientation of the cluster,causing<0001>texture to weaken.When forging in theα+βregion,both theαphases and residualβphases participated in deformation.As the number of forging passed in theα+βregion increases,lamellarαphases continued to become equiaxed,and the number of new equiaxedαphases transformed from the deformed residualβphases increases.The<0001>texture gradually weakened and shifted to<1010>and<1120>texture.The weakening of the macrotexture ofαphases mainly relied on the increase in newly formed equiaxedαphases.This was because the orientation shift of lamellarαphases caused by deformation was limited,while the orientations of equiaxedαphases formed by the transformation of deformed residualβphases were more varied.In addition,during the entire forging process,the equiaxation of lamellarαphases on the surface of the bar blank occurred more quickly,followed by the midradius position,and was the slowest in the center.This showed that the lower forging temperature and the more complex the stress state were more beneficial to the equiaxation ofαphases.The purpose of this article was to systematically and in-depth analyze the structure and texture evolution rules of theαphase andβphase during the forging process of TA19 titanium alloy,and to provide theoretical support for the optimization of bar preparation process.
作者
颜孟奇
佟健博
黄利军
郭鹏达
王振
Yan Mengqi;Tong Jianbo;Huang Lijun;Guo Pengda;Wang Zhen(Beijing Institute of Aeronautical Materials,Aero Engine Corporation of China,Beijing 100095,China)
出处
《稀有金属》
北大核心
2025年第8期1148-1158,共11页
Chinese Journal of Rare Metals
基金
国防科工局军品配套项目(JPPT-135-GH-2-017)资助。
