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用1 t真空自耗电弧炉试制出360 mm的TC19合金铸锭。采用常规β锻造+(α+β)锻造和高-低-高锻造(即β锻+(α+β)锻+β锻)两种锻造工艺,分别制备出相同规格的60 mm TC19钛合金棒材,锻棒微观组织细小均匀,均为在β转变基体上均匀分布的等轴初生α组织。对两种工艺的锻棒进行双重退火和固溶加时效处理,处理后的显微组织和力学性能均符合MIL-T-9047标准的要求。常规锻造工艺和高-低-高锻造工艺均可用来锻造TC19合金棒材,但采用高-低-高锻造工艺得到的棒材的力学性能优于常规锻造工艺。 相似文献
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研究了α+β锻造、近β锻造、β锻造3种锻造工艺对Ti-1300合金棒材组织和力学性能的影响。结果表明,锻造工艺对Ti-1300合金显微组织影响较大。经α+β锻造后,Ti-1300合金棒材的初生α相为细小等轴状,近β锻造后多为短棒状,β锻造后为沿晶界分布的尺寸较大的块状α相。经不同工艺锻造的Ti-1300合金棒材热处理后,近β锻造和β锻造的抗拉强度明显高于α+β锻造,同时β锻造后棒材的断裂韧性最高,近β锻造次之。本实验条件下,经β锻造的Ti-1300合金棒材抗拉强度达到1390 MPa,断裂韧性超过70 MPa·m~(1/2),是最优的锻造工艺。 相似文献
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α+β两相区轧制的TC4钛合金丝材经不同工艺热处理后,获得等轴组织、双态组织和片层组织,研究了微观组织特征及其对合金拉伸性能和疲劳性能的影响。结果表明:等轴组织α晶粒最为细小且具有较高的位错密度,表现出最高强度;双态组织α相较等轴组织显著长大,位错密度明显降低,具有最好的工艺塑性;片层组织原始β晶粒粗大,塑性最低。3种组织中片层组织疲劳性能最好,当裂纹长度<250μm时,不同显微组织对应的裂纹扩展速率差异较大,片层组织的扩展速率最低,等轴组织最高;当裂纹长度>250μm时,3种组织的裂纹扩展速率无显著差异。综合考虑TC4钛合金丝材的力学性能和工艺塑性,应选择双态组织作为产品的最终组织状态。 相似文献
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TC4钛合金根据锻造温度的不同,TC4锻造可分为α—β锻和β锻,在一般锻造中多在α—β两相区锻造,即β相变点(990℃左右)以下30-50℃的温区内锻造,其目的是要获得含一定比例α等轴晶粒的α+β组织,该组织具有较好的综合机械性能。β锻是指TC4或其它钛合金在β相变点以上进行锻造。TC4合金在β区锻造比在α—β区域锻造延伸率有所降低,虽然断面收缩率下降较多,但不低于一般高强合金钢,重要的是经β锻造,TC4合金的断裂韧性、高周疲劳性能和高温抗蠕变性能较好,见表1。 相似文献
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《粉末冶金工业》2021,(5)
本文采用真空热压烧结+热挤压+退火工艺制备细晶TC4钛合金,对制备过程中钛合金的微观组织与力学性能演变规律进行研究。结果表明,热压烧结态TC4钛合金主要由α和β相组成,α相以等轴状分布,而β相则以细长片层状/针状分布于α相晶粒内部或晶界处。热挤压可以使合金中的α和β相尺寸明显降低,形成板条状细晶,从而使TC4钛合金室温抗拉强度从热压烧结态的837 MPa提高至983 MPa,但此时TC4钛合金的断后伸长率最低,为9.6%。进一步的退火能够使热挤压态TC4钛合金发生回复和再结晶,β相由片层状/针状向颗粒状转变,分布于α相晶界处,从而有利于TC4钛合金塑韧性的提高。因此,经过热压烧结+热挤压+退火处理得到的细晶TC4钛合金具有较为优异的综合性能。 相似文献
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研究了两类锻造工艺对航天用TCA钛合金异形锻件的显微组织及拉伸性能的影响。其中Ⅰ类锻造工艺中第1火及第2火加热温度均在β单相区,Ⅱ类锻造工艺第1火加热温度在β相单区而第2火加热温度在(α+β)两相高温区。实验结果表明:Ⅰ类锻造工艺下最终得到具有粗大晶粒的片层组织,该类型组织强度及塑性均较低,不能满足指标要求;采用Ⅱ类锻造工艺即第2火加热温度在高温两相区且采用大锻造比可以获得条状α和细小等轴α构成的细小的混合组织,该组织具有较好的拉伸性能,满足指标要求。锻造时采用换向拔长镦粗的方式能保证异形锻件的宏观组织均匀。 相似文献
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S. L. Semiatin J. F. Thomas P. Dadras 《Metallurgical and Materials Transactions A》1983,14(11):2363-2374
The detailed relationships between thermal-mechanical processing parameters and resulting microstructures for Ti-6Al-2Sn-4Zr-2Mo-0.1 Si (Ti-6242) have been established through compression testing and heat treatment. Beginning with either an equiaxed alpha or Widmanstätten alpha preform microstructure, isothermal compression tests were run at strain rates typical of isothermal forging (10?3 to 10?1 s?1) and conventional forging (1 to 100 s?1). Metallographic investigation of these test specimens in as-deformed and heat treated conditions was used to characterize deformation-induced microstructures and transformations. For the equiaxed alpha microstructure, it was shown that deformation, as well as post-deformation heat treatment, were more effective in promoting microstructures close to the expected equilibrium ones than heat treatment alone, a finding similar to that for other alloy systems. For the metastable Widmanstätten alpha microstructure, the deformation and heat treatment parameters that promote the development of an equilibrium, equiaxed alpha microstructure have been determined. For this microstructure, two separate temperature-strain rate regimes have been identified, and the resulting microstructures correlated with the measured flow stress behavior. For the low temperature regime, deformation is highly nonuniform, and the microstructural features are shown to be similar to those in pearlitic steels and other lamellar alloys. In the higher temperature regime, on the other hand, deformation is much more uniform. The results presented can be applied to select hot forging parameters for the control of final microstructure and properties in Ti-6242 and similarα/β titanium alloys. 相似文献
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Brian D. Worth J. Wayne Jones John E. Allison 《Metallurgical and Materials Transactions A》1995,26(11):2947-2959
The influence of microstructure on creep deformation was examined in the near-y TiAl alloy Ti-49A1-1V. Specifically, microstructures
with varying volume fractions of lamellar constituent were produced through thermomechanical processing. Creep studies were
conducted on these various microstructures under constant load in air at temperatures between 760 °C and 870 °C and at stresses
ranging from 50 to 200 MPa. Microstructure significantly influences the creep behavior of this alloy, with a fully lamellar
microstructure yielding the highest creep resistance of the microstructures examined. Creep resistance is dependent on the
volume fraction of lamellar constituent, with the lowest creep resistance observed at intermediate lamellar volume fractions.
Examination of the creep deformation structure revealed planar slip of dislocations in the equiaxed y microstructure, while
subboundary formation was observed in the duplex microstructure. The decrease in creep resistance of the duplex microstructure,
compared with the equiaxed y microstructure, is attributed to an increase in dislocation mobility within the equiaxedy constituent, that results from partitioning of oxygen from the γ phase to the α2 phase. Dislocation motion in the fully lamellar microstructure was confined to the individual lamellae, with no evidence
of shearing of γ/γ or γ/α2 interfaces. This suggests that the high creep resistance of the fully lamellar microstructure is a result of the fine spacing
of the lamellar structure, which results in a decreased effective slip length for dislocation motion over that found in the
duplex and equiaxed y microstructures.
BRIAN D. WORTH, formerly with the Department of Materials Science and Engineering, The University of Michigan 相似文献
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研究了几种热处理制度对TC4-DT钛合金板材显微组织和力学性能的影响。结果表明:等轴或双态组织具有好的拉伸性能,片层组织能够有效提高材料的断裂韧性;控制单相区固溶的冷却速度以及第二重热处理的温度和冷却速度,可以获得不同尺寸的片层组织;单相区固溶后空冷,再经两相区第二重热处理,空冷的组织中含有粗的初生α片层和细小的次生α片层,炉冷的组织中α片层变厚,单相区固溶后水冷得到马氏体组织,在两相区热处理保温时,马氏体组织直接分解成粗的α片层。采用1 015℃/1 h/AC+955℃/1.5 h/AC+550℃/6 h/AC多重热处理,可以获得粗细相间的片层组织,具有更好的强度-塑性-断裂韧性的综合匹配。 相似文献
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通过水淬+空冷复合的方式,实现了在一个试样上淬火的冷却速度从水淬到空冷的不同,进而研究了冷却速度对TC2钛合金板材β淬火组织的影响。结果表明,β淬火时冷却速度不同,使得淬火后合金的金相组织存在较大的差别,进而对成品板材的组织产生影响。TC2合金板在热轧过程中获得了球状-纤维状的混合显微组织,水淬+空冷复合试样的水淬部分均发生马氏体转变,但转变的进程有所不同,水淬+空冷复合试样的空冷部分均为片状组织,随着冷却速度的降低,α片丛明显长大,α片宽度变大。淬火的延迟会导致板材显微组织不均匀。 相似文献
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冷轧态Ti-6Al-4V(TC4)合金经两种不同热处理制度处理之后,分别得到70%的等轴α相和30%的α+β片层组织(TC4-1)与25%的等轴α相和75%的α+β片层组织(TC4-2).等轴α相的晶粒尺寸分别为7.0±2μm和9.5±1.5μm.在室温下进行高压扭转,扭转过程中施加6.0 GPa的压力,扭转速度为1 r/min,分别扭转了1/4、5、10和20圈.随着扭转圈数和片层组织的增加,组织更为均匀.经20圈扭转变形后,TC4-1和TC4-2中的晶粒尺寸分别为115±30 nm和75±15 nm.随着片层组织的增加,显微硬度值显著升高.同时探讨了相比例对晶粒细化机制的影响. 相似文献