Tribological behaviors between commercial pure titanium sheet and tools in warm forming

The tribological conditions between tools and sheet are the major factors affecting the product quality,forming limits and service life of tools in thin-walled titanium components warm forming.Using the orthogonal design based twist compression test in the temperature range of 25-300 °C,the significant factors affecting the coefficient of friction（Co F） and the influencing rules in CP-3 titanium sheet warm forming are clarified and discussed by changing tribological conditions such as tool material,lubrication,temperature and normal pressure.The results show that the significant factors affecting the Co F are lubrication,surface roughness,tool material,sliding velocity,normal pressure and temperature;compared with unlubricated condition,the graphite and Mo S2 greatly improve the friction condition and the maximum reduction of the Co F is 0.318;the Co Fs of Cr12 Mo V/CP-3 and QAl10-3-1.5/CP-3 tribo-pairs show a similar tendency：the Co Fs increase with increasing surface roughness and sliding velocity,and increase firstly then decrease with increasing normal pressure and temperature.

Prediction of forming limit curve for pure titanium sheet

Commercially pure titanium（CP Ti） has been actively used in the plate heat exchanger due to its light weight, high specific strength, and excellent corrosion resistance. However, researches for the plastic deformation characteristics and press formability of the CP Ti sheet are not much in comparison with automotive steels and aluminum alloys. The mechanical properties and hardening behavior evaluated in stress-strain relation of the CP Ti sheet are clarified in relation with press formability. The flow curve denoting true stress-true strain relation for CP Ti sheet is fitted well by the Kim-Tuan hardening equation rather than Voce and Swift models. The forming limit curve（FLC） of CP Ti sheet as a criterion for press formability was experimentally evaluated by punch stretching test and analytically predicted via Hora＇s modified maximum force criterion. The predicted FLC by adopting Kim-Tuan hardening model and appropriate yield function shows good correlation with the experimental results of punch stretching test.

Head Curvature of Pure Titanium Sheet Influenced by Process Parameters and Controlling in Hot Rolling Process

We investigated the influences of process parameters on the head curvature of pure titanium sheet in hot rolling process and proposed the controlling means. First, the thermal simulation experiments for pure titanium TA1 were carried out to investigate the hot deformation behaviors of pure titanium in the temperature range of 700-800 ℃ with strain rate range of 1-20 S-1, and the processing map was established to determine optimized deformation parameters. Then, the finite element model has been constructed and used to analyze the effect of process parameters on the direction and severity of head curvature of pure titanium sheet. The process parameters considered in the present study include workpiece temperature, work roll diameter, pass reduction, oxide scale thickness of workpiece surface, and interface friction coefficient. The simulation results show that the workpiece temperature and the interface friction coefficient are the two main factors. The proposed controlling means was carried out on a hot rolling production line and solved the head curvature problem effectively. The rolling practices indicate that the rolling yield is improved greatly.

Improvement and Experiment of the Reamer in Vibra Cutter Against Wave Edge of Titanium Sheet Alloy Parts

By analyzing the influencing factors of part quality making of sheet alloy of titanium by vibra cutter, the shape of upper reamer is set as cylinder and wedge-shaped form, and the lower reamer as plain and hemicycle form, and its main structural parameters are defined as well. Then it is validated further that such improved vibra cutter reamer can be used to process curve-edged parts of titanium alloy sheet. The experimental result shows that the titanium alloy sheet parts processed by above equipment have no sharpen angles for convex parts and evident crevasse of concave-edged part. In summary, such improvement can eliminate the free-waved edge and improve the manufacture quality of titanium alloy sheet parts greatly.

Relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation

The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flow stress and sound plasticity,and increasing the heat treatment temperature resulted in an increased ultimate tensile strength(UTS)and a decreased elongation(EL).The deformation mechanism of TA32 alloy was dominated by high angle grain boundaries sliding and coordinated by dislocation motion.The coarsening of grains and the annihilation of dislocations in heat-treated specimens weakened the deformation ability of material,which led to the increase in flow stress.Based on the high-temperature creep equation,the quantitative relationship between microstructure and flow stress was established.The grain size exponent andαphase strength constant of TA32 alloy were calculated to be 1.57 and 549.58 MPa,respectively.The flow stress was accurately predicted by combining with the corresponding phase volume fraction and grain size.Besides,the deformation behavior of TA32 alloy was also dependent on the orientation of predominantαphase,and the main slip mode was the activation of prismaticslip system.The decrease of near prism-oriented texture in heat-treated specimens resulted in the enhancement of strength of the material.

Effect of high density electropulsing treatment on formability of TC4 titanium alloy sheet

An annealed TC4 titanium alloy sheet was treated by high density electropulsing(Jmax=(5.09-5.26)×103A/mm2,tp=110μs)under ambient conditions.The effect of electropulsing treatment(EPT)on the plastic deformation behavior of TC4 titanium alloysheet was studied using uniaxial tension tests.The experimental results indicate that electropulsing treatment significantly changesthe mechanical properties of sheet metal:the uniform elongation is increased by 35%,the yield stress is decreased by 19.8%and theyield to tensile ratio is decreased by 17.6%.It is of significant meaning to improve the formability of TC4 titanium alloy sheet.Theoptical microscope and scanning electron microscope(SEM)were used to examine the changes of the microstructure and the fracturemorphology before and after the electropulsing treatment.It is found that recrystallization occurs in the sheet metal and dimples infracture surface are large and deep after the electropulsing treatment.The research results show that the electropulsing treatment is aneffective method to improve the formability of titanium alloy sheets.

Deformation behavior of TC1 titanium alloy sheet under double-sided pressure

In order to investigate the influence of normal stress through thickness on the formability of sheet metal,the viscous pressure bulge(VPB)tests of an annealed TC1 titanium alloy sheet were carried out under two different conditions:double-sided pressure bulging and conventional single-sided pressure bulging.The automated strain analysis,measurement environment(ASAME)and scanning electron microscope(SEM)were used to study the strain distributions and the fracture morphology of bulged specimens.It is found that thickness strain is increased for double-sided pressure bulging specimens,and the limiting dome height(LDH)of double-sided pressure bulging specimens is increased by 31.8% compared with conventional single-sided pressure bulging specimens.The dimples in fracture surface for double-sided pressure bulging specimens are larger and deeper than those for conventional single-sided pressure bulging specimens.The results indicate that normal stress through thickness is helpful in improving the formability of titanium alloy sheet metal.

Research on microstructure and property of electron beam welding joints of titanium alloy sheets

This paper reports research into the microstructures and properties of electron beam welding （EBW） joints of a Ti alloy sheet. To control the TC4 sheet joint formation during electron beam welding is not an easy task. However, the electron beam current has a significant influence on joint formation and a good appearance of a T-joint can be obtained by increasing the heat input and using the electron beam scan method. It was found that all acicular martensite in the fusion zone （FZ） consisted primarily of α＇ phase titanium, with some β phase present. Grain coarsening occurred in the heat-affected zone （HAZ） due to transformation of the β phase. Butt joints possessed high strength, hardness of the fusion zone, and the heataffected zone of these joints performed better than that of the parent metal. The highest shear strength of T-joint was 615 MPa and the fracture mechanism was a gliding fracture.

Photocatalysis of TiO2 Sheets Prepared by Templating Filter Paper

Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared spectroscopy, surface area analyzer, thermogravimetric analysis, powder X-ray diffraction, and scanning electron microscopy. The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in an aqueous solution under UV-illumination. The results demonstrated that the paper-like TiO2 sheets with the optimum proportion of anatase/rutile （10/1） had the highest photoactivity. And the presence of the filter paper fiber can improve the crystallinity, raise the anatase-rutile transformation temperature and contribute to the formation of being paper-like. A detailed formation mechanism for TiO2 sheets is proposed.

Effect of rolling and heat treatment on microstructure and properties of Ti-26 sheet

The effect of heat treatment and rolling process on the properties and microstructures of Ti-26(Ti-15V-3Al-3Cr-3Sn-Forming) sheet was studied. The results show that the best rolling temperature for Ti-26 alloy is in the temperature range from 900 ℃ to 950℃. Under this condition,the resistance of deformation and yield ratio are low and the alloy has better hot work ability. The alloy will achieve better mechanical properties and completely recrystallized β microstructure when the deformation ratio is not less than 60% and the solution temperature is 30 ℃ above the phase transformation temperature. The best heat treatment conditions are recommended as:790℃,30 min,AC or WQ followed by 510 ℃,10 h,AC. Under this heat treatment condition the strength of the Ti-26 alloy is 1 230 MPa and the elongation is 15%.

冷轧TA1钛板的塑性变形行为研究

借助电子背散射衍射技术(EBSD)和X射线衍射仪(XRD),研究了冷轧TA1钛板在不同压下率下表层和中心层的微观组织、织构及形变孪晶的演变规律,分析了其塑性变形行为。结果表明,随着冷轧压下率的增大,表层和中心层的等轴晶粒均逐渐转变为纤维状组织。在中低变形率范围(0%~40%),组织中观察到{1122}<1123>压缩孪晶和{1012}<1011>拉伸孪晶,孪晶数量则随着压下率的增加先增多后减少,在压下率为20%时达到最大值。冷轧样品表层和中心层主要含有{0001}基面织构和{1120}面织构,以及{0112}<1000>、{1125}<1100>、{1123}<1100>三种棱锥织构。随着压下率的增大,{0001}基面织构含量先增多后减少,{1120}柱面织构无明显变化,三种棱锥织构的含量则呈增加的趋势。整体而言,在冷轧过程中,中心层的织构组分含量变化较小,而表层的织构组分变化较大,且呈现逐步增强的趋势,最终表层和中心层织构的组分含量趋于一致。

热处理温度对TA15钛合金板材组织及性能的影响

本研究对冷加工态TA15钛合金板材进行了750℃、800℃、850℃和900℃四种温度的热处理,并深入探讨了处理后的显微组织、室温拉伸性能、弯曲性能、洛氏硬度和高温性能。结果显示,在750℃时,板材的横向为等轴组织,纵向含有少量拉长组织;而在800℃至900℃范围内,板材的横向和纵向均形成了均匀细小的等轴组织。随着热处理温度从750℃升至850℃,板材的拉伸强度逐渐降低,而伸长率、弯曲角度则有所增加,洛氏硬度逐渐下降。值得注意的是,800℃至850℃热处理的板材显示出优异的综合性能,特别是850℃热处理的板材已完全再结晶。因此,建议TA15钛合金冷轧板材在这个温度范围内进行热处理,以获得最佳的显微结构和力学性能。

基于ABAQUS的钛合金管板焊接过程模拟仿真

针对蒸汽发生单元钛合金管板焊接过程中焊接变形预测与控制问题,开展了焊接过程有限元仿真研究。基于顺序耦合的热弹塑性有限元法,采用ABAQUS对典型管板结构进行了不同焊接顺序下的焊接仿真分析,利用校核后的组合热源定义热流密度函数,计算得到焊接温度场、应力场及变形。结果显示,采用高斯热源与椭球体组合热源可以较为精确模拟熔池形貌,管板焊缝区域存在应力集中,且应力峰值位于管板被夹持区域,大小为631.2 MPa,超过材料屈服极限。单个环焊缝在不同路径下的应力分布因受到周围焊缝热输入的影响而出现复杂波动。采用从上至下的对称焊接顺序可以有效减小焊接变形量,最大变形量降幅可达24.3%,为后续工艺优化提供了参考依据。

退火温度对Gr.4纯钛薄板微观结构及力学性能的影响研究

对冷轧后的Gr.4纯钛薄板进行不同温度的退火处理,利用电子背散射衍射技术(EBSD)分析其晶粒尺寸、晶界分布、位错密度和微织构,并讨论它们与力学性能之间的关系。结果表明:在740、780、820℃退火温度下,Gr.4纯钛薄板的晶粒尺寸差别不大;退火后可能存在10.53°、60°、60.83°、63.26°、90°5种α/α取向差角度,并且表现出随机性;α晶粒内的位错密度随着过冷度的上升而变小;在780℃退火条件下,呈现出最强的<0110>织构,即Ti原子最密排方向,其抵抗位错滑移的能力最强,因而强度最大,且强塑性匹配较好。

双向拉伸试验的进展与钛板双向拉伸的强化研究

本文研究了双向拉伸的各种装置、试件和试验方法 ,以及它们各方面的进展 .同时推导出双向拉伸下的各向异性虎克定律和屈服条件 ,并对钛板作了相应的专题研究 .

钛粉粒度对轧制烧结多孔钛板力学性能的影响

对不同粒度钛粉的流动性、松装密度和振实密度进行分析,经轧制和烧结制备出满足湿法冶金需求的多孔钛板,研究了钛粉粒度对轧制烧结多孔钛板力学性能的影响。结果表明:轧制烧结多孔钛板的最大孔径和孔隙度随钛粉粒度的减小而减小,钛板密度、剪切强度、抗弯强度、抗拉强度及伸长率均随钛粉粒度的减小有所增加;当钛粉粒度范围为89~104μm时,粉末轧制烧结多孔钛板的综合力学性能较高。

钛合金板料激光曲线弯曲及热辐射对其组织性能的影响

研究了激光能量密度、路径曲率和扫描次数对 ＴＣ４（Ｔｉ－６Ａｌ－４Ｖ）板料弯曲变形的影响规律同时，分析了热辐射对板 料显微组织和表面硬度的影响．结果表明：（１）存在一个最优的能量密度值使板料一次弯曲所获得的弯曲角度达到峰值；（２）随 路径曲率的增加，弯曲角度减小；（３）第一次扫描以后的扫描次数与弯曲角度呈准线性关系；（４）合适的工艺参数不会导致材料显微组织变化，且激光热辐射对材料表面有淬火效应，使加热区材料表面硬度均有所提高．

钛板的张力冷轧研究

针对钛板在无张力条件下冷轧效率低下的问题,首先结合钛材力学性能各向异性的特点,以Hill异性屈服准则为基础,推导出钛板在张力冷轧下的应力状态方程,从而在理论上阐明,钛板在张力条件下进行冷轧的可行性主要取决于其塑性变形条件及其所处的应力状态.然后在实验室的四辊可逆冷轧实验机上对钛板进行了张力冷轧实验研究.实验结果表明,钛板在适当的张力作用下冷轧,能够在保证良好板形的前提下实现单道次大压下量轧制,极大地提高了轧制效率.

TC1M钛合金板材拉深成形过程中的形状畸变

采用有限元数值模拟与成形工艺实验相结合的方法,对0.84mm厚的TC1M钛合金板材杯形件室温拉深成形及回弹过程进行了研究.结果显示,拉深制件不仅出现凸耳和杯口厚度不均等熟知的现象,还揭示出因钛合金各向异性所引发的杯口内壁非圆化,这类形状畸变对制件的几何精度将产生不利影响.600℃温热拉深能有效地抑制卸载回弹,杯口内壁非圆化得以消除,但却无法改变钛板的各向异性性质,凸耳和杯口厚度不均等畸变现象依然存在.

Sb掺杂钛基SnO_2电极的制备、表征及其电催化性能研究

采用电沉积 热氧化法制备了含有中间层的Sb掺杂钛基SnO2 电催化电极(Ti/SnO2),采用SEM、EDX以及 XRD 等检测方法对所制备电极的表面形貌、元素组成及结构进行分析,并以苯酚为目标有机物,研究所制备电极对有机污染物的电催化降解能力。研究结果表明所制备 Ti/SnO2 电极可在较短时间内将苯酚彻底降解,其较大的真实表面积以及电极中间层的存在是所制备电极性能提高的重要原因。阳极极化曲线扫描(LSV)的分析结果表明所制备的 Ti/SnO2电极具有较高的阳极析氧电位,有利于有机物的阳极氧化降解。