TA32钛合金超塑性变形行为及本构模型研究

通过单向拉伸实验研究了TA32钛合金在温度880~940 ℃、初始应变速率5×10-4~1×10-2 s-1条件下的超塑性变形行为和微观组织演变,构建了修正Johnson-Cook本构模型和BP神经网络本构模型。结果表明,TA32钛合金的流动应力与断后伸长率对温度和应变速率敏感,应变速率敏感性指数随应变量增加而减小,随温度升高而增大。温度升高和变形程度增大促进了α→β相转变和两相晶粒长大,应变速率降低使得两相晶粒有所长大。β相晶粒形貌随变形条件改变有显著变化,α相晶粒则保持等轴状。TA32钛合金的超塑性断裂模式为孔洞生长扩展导致的微孔聚集性断裂。相较于修正Johnson-Cook本构模型,BP神经网络本构模型在大范围变形条件下的预测精度更高。     

TA15钛合金热剪旋件的几何精度与显微组织分析(英文)

为了揭示偏离率和加热温度对TA15钛合金加热剪切旋压件的影响机制,研究了不同偏离率下热剪旋件的几何精度和微观组织。结果表明:在负偏离下工件会发生径缩,且温度的突然降低会使径缩更严重。在正偏离条件下且加热温度缓慢降低时,沿工件底部到口部有明显扩径。沿热剪旋工件厚向的不均匀变形使工件晶粒细化且近外层晶粒比近内层晶粒细小。在近外层可能形成纤维组织,该纤维组织的扭曲程度随着偏离率的减小而增加。近零偏离和保持加热温度在合理范围时有利于获得几何精度高和微观组织均匀的工件。     

Flow behavior and microstructure evolution during hot compression of TA 15 titanium alloy

The samples of TAI 5 titanium alloy were hot compressed in the temperature range of 550-1 000 β at constant strain rate from 0.01 s^-1 to 1.0 s^-1. The flow behavior and microstructural evolution during hot deformation of TA 15 alloy were investigated, based on which the hot working parameters of TA15 alloy were selected. The results show that with the increase of deformation temperature and decrease of stain rate, the flow stress decreases gradually, but the magnitude of stress drop varies with the increase of temperature in different temperature intervals. According to the flow stress and deformation microstructure, the deformation behavior can be classified into three types as working hardening（550-600 β, α＋β phase）, dynamic recrystallization （650-900 ℃, α＋β phase） and dynamic recovery（950-1 000 ℃, β phase）. The main softening mechanism is dynamic recrystallization（DRX） of a phase in α＋β phase zone and dynamic recovery（DRV） of β phase in β phase zone. As the stain rate decreases dynamic recrystallization of a phase proceeds more adequately in α＋β zone and the β subgrains of dynamic recovery have the tendency to grow infl zone. The reasonable temperature for warm forming of TA15 alloy is in the range of 600-700 , which has been verified by warm spinning experiment of tube workpieces.：     

TA15钛合金A-TIG焊接头组织和性能分析

以CaR与MgF2的混合物为活性荆，对TA15钛合金A-TIG焊接头组织和性能进行了分析，并和常规TIG焊进行了比较。结果表明：A-TIG焊能够有效减少气孔数量，提高接头的抗拉和抗弯性能；与常规TIG焊相比，A-TIG焊HAZ较窄且组织较细，而二者的焊缝区组织基本相同；活性荆的加入并没有降低A—TIG焊接头的耐腐蚀性能。     

Influence of deformation parameters on microstructure and mechanical properties of TA 15 titanium alloy

The influence of deformation parameters including deformation temperature, degree and speed on the microstructure and mechanical properties of TA15 titanium alloy was studied. The volume fraction, size and aspect ratio of primary a phase in deformed TAI 5 titanium alloy were quantitatively characterized. With increasing deformation temperature, the volume fraction and size of primary α phase decrease. The aspect ratio of primary a phase decreases with increasing deformation temperature. The tensile strength of TA15 alloy deformed at 0.1 mm/s is higher than that at 0.3 mm/s. After therlnoforming at 960℃, 0.1 mrn/s, the tensile strength is the highest up to 1 035 MPa and the elongation is 13.5%. When the thermoforming temperature is 1 050℃, the strength and elongation are both relative low, because the microstructure is Widmanstaten structure.     

退火工艺对TA15钛合金板三向硬度及显微组织的影响

对TA15钛合金薄板进行了退火处理,然后测试了板材的三向（板面法向、横向、纵向）硬度,同时观察了退火温度和时间对板材组织的影响。结果表明,板材具有明显的各向异性,板面硬度高于纵、横向硬度;同时,板硬度随着退火温度提高,至850℃硬度降至最低。金相观察表明,在850℃以下的组织无区别,高于850℃组织变化明显,920℃时为双态组织。     

多次加热成形对TA15钛合金复杂锻件组织性能的影响

研究了TA15钛合金复杂锻件多次加热成形时,小变形/无变形区的组织性能变化。结果表明,同一温度下,随加热次数增加,试验件强度塑性略有下降,加热次数对拉伸性能的影响不明显;加热温度对试验件性能影响明显,温度增高,强度降低。多次加热时,变形量大的试验件强度低于变形量小的试验件。为保证大型复杂锻件组织性能均匀性,多次锻造加热温度不宜高。     

Effect of spinning deformation on microstructure evolution and mechanical property of TA 15 titanium alloy

Hot spinning of tubular workpiece of TAI5 alloy was conducted on a CNC spinning machine, and the microstructure evolution during hot spinning and annealing was observed and mechanical properties of spun tubes were tested. The results show that with the increase of spinning pass, the fiber microstructure comes into being gradually in axial direction and the circumferential microstructure also stretches obviously along circumferential direction. At the same time, the tensile strength increases and elongation decreases not only in axial direction but also in circumferential direction. When the reduction ratio of wall thickness rises close to or over 40%, tensile strength increases and elongation decreases more rapidly, which means that tubular workpiece of titanium alloy can be strengthened bi-directionally by power spinning. The ductility of spun workpiece of TAI5 alloy could be improved by annealing at the temperature no higher than recrystallization temperature with slight decrease of tensile strength.     

TA32钛合金板材的超塑性能研究

研究了真空环境中TA32钛合金板材在温度950℃、应变速率5. 32×10~(-4)～2. 08×10~(-2)s~(-1)条件下的超塑性变形行为。结果表明,在不同应变速率条件下,合金的流变应力曲线特征和显微组织演变显著不同。在应变速率较低(5. 32×10~(-4)～3. 33×10~(-3)s~(-1))条件下,拉伸真应力-真应变曲线呈传统超塑变形的稳态流动特征,变形后的合金中初生α相晶粒尺寸较大;在高应变速率(8. 31×10~(-3)s~(-1)～2. 08×10~(-2)s~(-1))条件下,拉伸真应力-真应变曲线中流变应力增大到峰值后快速单调递减直至试样断裂,合金变形过程中初生α相发生动态再结晶,晶粒尺寸较低应变速率条件下显著细化。950℃时,TA32钛合金板材均具有超塑性变形能力,超塑性延伸率在145%～519%之间;当应变速率为5. 32×10~(-4)s~(-1)时,具有最佳的超塑性,拉伸延伸率可达519%。断裂区形貌分析发现,TA32钛合金板材的超塑性断裂模式为空洞聚集-连接-长大型断裂。     

复合形变热处理对TA15近α钛合金组织和性能的影响

研究等温变形的条件下形变热处理对TA15近α型钛合金显微组织细化的效果。结果表明,复合形变热处理可明显细化TA15钛合金的显微组织,并在一定程度上改善TA15钛合金的综合力学性能。单相区的高温形变热处理可细化β晶粒并获得细针状马氏体α’和亚稳态的β相,两相区较低温度的形变热处理,可进一步细化由α’马氏体和亚稳β相分解而来的细针状α＋β相。经过复合形变热处理,TA15钛合金的室温性能和高温性能均有所提高,其中高温持久性能提高幅度较大,但是室温伸长率稍有下降。复合形变热处理是细化钛合金显微组织和提高力学性能的有效途径。     

变形参数对TA32合金的超塑性变形行为及微观组织演化的影响

针对我国自主研制的TA32高温钛合金,开展了在变形温度为895-935℃和应变速率为8.3×10_-4-1.32×10-2 s_-1条件下的高温拉伸变形试验研究,利用电子背散射技术(EBSD)表征了不同变形条件下的晶粒形貌、晶粒取向和分布规律。结果表明：TA32合金具有良好的超塑性变形能力,最大断裂延伸率能达到1141.8%。在高温和低应变速率条件下,晶粒的长大容易造成在变形后期真实应力出现上升现象。真实应力和断裂延伸率对变形温度、变形程度和应变速率均是敏感的,动态再结晶容易在高温或低应变速率条件下发生。动态再结晶程度随着变形温度的升高、应变速率的降低和变形程度的增大而增大,变形后的织构接近随机取向织构,原始晶粒得到等轴化,提高了晶粒尺寸的均匀性。在变形过程中,不连续动态再接晶是主要的动态再结晶机制,随着变形温度的升高、应变速率的降低和变形程度的增大,不连续动态再结晶的作用在增强,连续动态再结晶的作用则是在减弱。     

TA15钛合金的形变热处理

研究了形变热处理对TA15钛合金组织与力学性能的影响。在α＋β两相进行形变热处理使组织中的条状初生α相碎化。对水冷的试样进行930℃／1h／空冷＋915℃／1h／空冷＋530℃／6h／空冷的处理，抗拉强度明显提高，组织中的条状初生α相发生球化。在β相进行形变热处理使强度略有降低，魏氏组织中的α层片增厚。     

细晶1420铝锂合金超塑性能试验研究

文章以采用双级时效制度和转向轧制工艺制备的细晶1420铝锂合金为研究对象,通过恒应变速率超塑拉伸试验,研究了合金的单轴超塑拉伸性能。结果表明,在460℃~520℃温度条件下和1×10-4s-1~5×10-3s-1应变速率范围内,细晶1420铝锂合金表现出良好的超塑性,在温度460℃、应变速率1×10-4s-1条件下,延伸率达到650%。利用光学显微镜和透射电镜等检测手段,对超塑变形后材料的组织进行了观察和分析。     

显微组织对TA11钛合金棒材力学性能的影响

通过对TA11钛合金不同组织状态的棒材进行组织、性能检测分析,研究了初生α相含量和尺寸对TA11钛合金室温拉伸性能、热稳定性能、蠕变性能的影响。研究结果表明,初生α相含量对TA11钛合金的拉伸性能影响较小,但对合金的抗蠕变性能影响明显:初生α相含量在50%~90%范围内时,合金的室温拉伸性能、热稳定性能随初生α相含量的增加变化不明显,抗蠕变性能随初生α相含量的增加而提高;初生α相尺寸对TA11钛合金的拉伸性能、蠕变性能具有一定的影响,随着组织粗大程度的增加,拉伸强度降低,抗蠕变性能提高。     

TA15钛合金零件热校形方法

研究了真空重复退火对TA15钛合金组织性能的影响;基于TA15钛合金典型零件,对其变形校正方法、校正工艺参数进行了分析。结果表明,TA15钛合金随着重复退火次数的增加,材料强度略有下降,塑性略有上升,但变化幅度不大;随退火次数增加,合金再结晶程度更加完全,残留β相的分布更加弥散,组织类型未发生变化,合金组织稳定,TA15钛合金零件可以采用热校形的方法进行变形校正。经对典型零件热校形,确定了TA15钛合金的热校形工艺参数。     

Superplastic characteristics of fine-grained 7475 aluminum alloy

A 7475-aluminum alloy was subjected to a thermomechanical heat treatment that resulted in a final recrystallized grain size on the order of 10 μm. Tensile specimens of dimensions 10 × 4 × 2.3 mm were machined such that the tensile axis was parallel to the rolling direction. Tensile tests were carried out at high temperatures in the range of 773 to 803 K at different cross-head speeds corresponding to initial strain rates in the range of 10⁻⁴ to 10⁻² s⁻¹. Elongations of several hundred percent were observed at strain rates of <10⁻³ s⁻¹. The correlation between flow stress and strain rate suggests that the strain rate sensitivity m is close to 0.5 at the lower strain rates. The value of m decreases to ≈0.2 at high strain rates. The decrease in m suggests a transition in the rate-controlling process from superplastic deformation (m ≈ 0.5) to dislocation creep (m ≈ 0.2) with increasing strain rate. The calculated activation energies in the two deformation regions are consistent with the suggested rate-controlling processes.     

TA15钛合金棒材在加热和冷却过程中的相转变

采用空冷保留高温组织状态的方法,研究TA15钛合金棒材在β相区和两相区加热和冷却过程中的相转变。结果表明,在两相区加热时,随着温度的升高,次生α相(α_s)逐渐减少,β相逐渐增多,晶粒形态均为等轴状;当加热至β相区温度,等轴状的初生α相明显减少,次生α和β相由等轴状转变为层片状。在冷却过程中,初生α相优先长大;次生α相在较低温度下通过形核析出长大。此时初生α相的长大将受到限制;随着保温温度的降低,次生α相的析出温度降低。     

TA15钛合金强热旋微观组织演变(英文)

研究TA15钛合金热强旋过程中的微观组织演变,探讨壁厚减薄率对TA15钛合金微观组织演变的影响。变形过程中,滑移变形是主要的变形机制,孪晶起到协调变形的作用。微观结构逐渐转变为细小的纤维组织,并且初生α晶粒的长径比随着壁厚的减薄而增加,再结晶分数和显微硬度也随着减薄率的增加而增加。     

TB6钛合金定m值法高温超塑性拉伸试验研究

在以往TB6钛合金研究成果的基础上,自行开发出定m值法超塑性拉伸控制程序来研究TB6钛合金的超塑性能,该控制程序具有自行拉伸控制、实时数据采集、分析处理和绘制监控曲线等功能。对该程序进行充分调试后,将TB6钛合金试样放在最佳变形温度750℃的条件下,设置拉伸程序中的应变速率敏感指数m值分别为0.30,0.35,0.40和0.45进行高温拉伸试验,采集数据得到TB6钛合金伸长率A分别为285%,318%,337%和367%。通过分析试验结果,绘制了应变速率敏感指数m值与伸长率A的关系曲线,再经回归分析,得到TB6钛合金超塑性应变速率敏感指数m值与伸长率A的关系式。