Optimization of dressing infeed of alumina wheel for grinding Ti-6Al-4V

In the present experiment study, dressing infeed values of 5, 10, 15, 20, and 25?µm are conceived on alumina wheel using 0.75 carat identical diamond dressers. The surface topologies of the dressed wheels are observed under scanning electron microscope. Differently dressed wheels are subsequently, employed for up-grinding Ti-6Al-4V in dry environment for 20 passes while the grinding infeed is kept constant at 10?µm during each pass. The grinding ratio is evaluated and the typical surface roughness parameters are measured using a mechanical type stylus. Tangential and normal force components are accurately measured with the help of dynamometer while the quality of ground substrate is observed under high resolution microscope. The performances of the differently dressed wheels are evaluated and subsequently, the dressing parameters are optimized based on the results obtained herein.     

Impact of dressing infeed on SiC wheel for grinding Ti-6Al-4V

Present experimental investigation is directed toward the optimization of dressing infeed for silicon carbide (SiC) wheel to be employed for grinding difficult-to-machine super alloy Ti-6Al-4V. Grinding wheels are dressed using separate, however, identical 0.75 carat single point diamond dressers at 5, 10, 15, 20 and 25 µm infeed values. Differently dressed wheels are consequently, applied for grinding Ti-6Al-4V under different infeed values of 5, 10 and 15 µm. All the operations have been performed at a constant velocity of 1810 m/min. The performances of the differently dressed SiC wheels are evaluated based on the variations of grinding force components, average surface roughness values, grinding ratio, chip forms and based on the analyses of the micrographs of wheel topologies and also of the ground surfaces, obtained using scanning electron microscope. Following the performance evaluation, the optimized dressing infeed has been found to be 20 µm for the operation range considered herein.     

Ti3Al基合金与Ti-6Al-4V合金TLP连接接头的组织转变

采用TiZrNiCu合金作为中间层材料研究了Ti3Al基合金与Ti-6Al-4V合金的瞬间液相(TLP)扩散连接接头成分、组织转变及显微硬度.研究结果表明,连接温度和连接时间对接头成分和组织有较大的影响.随着连接温度的提高和连接时间的延长,接头中元素分布趋于均匀,连接区宽度增大.连接温度为850℃和900℃时,液相的残留使得接头中存在Ti-Cu金属间化合物.当连接温度为950℃,连接时间为30min时,等温凝固的完成使Ti-Cu金属间化合物从接头中消失.随着连接温度的提高和连接时间的延长,接头连接区硬度降低.当连接温度为950℃,连接时间为30min时,接头硬度分布较均匀.     

Effect of mean stress on fretting fatigue of Ti-6Al-4V on Ti-6Al-4V

Fretting fatigue tests of Ti‐6Al‐4V on Ti‐6Al‐4V have been conducted to determine the influence of stress amplitude and mean stress on life. The stress ratio was varied from R=−1 to 0.8. Both flat and cylindrical contacts were studied using a bridge‐type fretting fatigue test apparatus operating either in the partial slip or mixed fretting regimes. The fretting fatigue lives were correlated to a Walker equivalent stress relation. The influence of mean stress on fretting fatigue crack initiation, characterized by the value of the Walker exponent, is smaller compared with plain fatigue. The fretting fatigue knockdown factor based on the Walker equivalent stress is 4. Formation of fretting cracks is primarily associated with the tangential force amplitude at the contact interface. A simple fretting fatigue crack initiation metric that is based on the strength of the singular stress field at the edge of contact is evaluated. The metric has the advantage in that it is neither dependent on the coefficient of friction nor the location of the stick/slip boundary, both of which are often difficult to define with certainty a priori.     

Fracture mechanics based fretting fatigue life predictions in Ti-6Al-4V

A fracture mechanics based crack propagation analysis is developed to work directly with the output of a contact mechanics stress analysis for fretting fatigue. A series of remote load fatigue tests were conducted on specimens that had previously been subjected to fretting fatigue loading conditions. The growth of these prior fretting induced cracks were monitored and compared to results from the crack propagation analysis. A combined fatigue crack formation and propagation analysis was then applied to other fretting fatigue experiments with good success. The creation of fretting fatigue stress-life curves is also demonstrated.     

Failure analysis of a Ti-6Al-4V rotating main rotor component from an army helicopter

This paper discusses the failure analysis of a Ti-6Al-4V rotating main rotor component and contrasts the perspectives of the design/mechanical engineer and the manufacturing/materials engineer. Cracking initiated at mechanical marks located on the surface of the outer diameter of a planetary post at the transition radius and was propagated by high-cycle fatigue in service. These crack initiation defects were most likely produced by a machining or a surface finishing tool. Fractographic evidence suggests that high stresses were also encountered in service and played a significant role in the premature cracking of these components. The debate centers on whether the components would have failed in the absence of the surface defects. There were several manufacturers of this component, which are compared in this study. The workmanship on the outer diameter of the planetary post at the transition radius of a carrier that had not failed, manufactured by Company B, was superior to that of the two cracked carriers produced by Company A. However, analysis of the service conditions indicates that the components may have been loaded near the yield strength of the material.     

The effect of angle on dovetail fretting experiments in Ti-6Al-4V

The objective of this work was to compare the fretting fatigue performance of Ti‐6Al‐4V dovetail specimens on Ti‐6Al‐4V pads having various contact angles typical of engine hardware; 35°, 45° and 55° dovetail angles were considered. The dovetail fixtures were instrumented with strain gages so that the local normal and shear contact forces could be calculated. The contact force hysteresis loops were recorded showing the stick‐slip history. At R= 0.1, gross slip was observed for several thousand cycles followed by partial slip after the average coefficient of friction increased. At R= 0.5, gross slip was present only during the first half cycle. During partial slip, the slope of the shear versus normal force was a function of the dovetail angle. The local contact loads, therefore, differed for the same remotely applied force. Despite this, the fretting fatigue life depended primarily on the remotely applied load not dovetail angle.     

Evaluating application potentiality of unconventional fluids for grinding Ti-6Al-4V using alumina wheel

Conventional metalworking fluids carry an acute threat to the environment as these produce a hazardous ambiance. Furthermore, due to their excessive use and imprudent disposal, the risk of environmental pollution exaggerates. The present article is aimed at finding some alternative potential coolants to be applied in small quantity lubrication (SQL) mode for grinding of difficult-to-machine (DTM) material, titanium alloys, which could effectively replace the conventional metalworking fluids while ensuring minimal waste of the coolant. Three unconventional environmentally safe coolants viz. alkaline soap water, sodium nitrite, and propylene glycol are applied in SQL mode while grinding Ti-6Al-4V. Comparative performance analyses of these cutting fluids have been adjudicated, considering responses of force required for material removal, substrate roughness, grinding ratio, and SEM micrographs of chips and ground surface. The results reveal that the environment-friendly unconventional fluids perform better than the conventional Blasocut fluid and the most satisfactory operations are observed under propylene glycol environment on the basis of the relevant parameters and operating range considered herein.     

TI-6Al-4V合金置氢-除氢组织与力学性能

为研究除氢处理对置氢钛合金组织与性能的影响,对Ti-6Al-4V合金在不同参数条件下进行了置氢与除氢处理,采用光学显微镜分析了置氢-除氢处理过程中Ti-6Al-4V合金微观组织的演化规律,通过室温拉伸试验研究了置氢-除氢处理后Ti-6Al-4V合金的力学性能,探讨了Ti-6Al-4V合金置氢-除氢组织与力学性能之间的相...     

A study on the hot corrosion behavior of Ti-6Al-4V alloy

The titanium alloys are potential materials for high temperature applications in turbine components due to their very high temperature strength and lightweight properties. However, hot corrosion is a life-limiting factor when Ti alloys are exposed to different chemical environments at high temperature. In the present paper, hot corrosion behavior of Ti-6Al-4V (Ti-31) alloy in different salt environments viz. air, Na₂SO₄-60% V₂O₅ and Na₂SO₄-50% NaCl at 750 °C was studied. The parabolic rate constants were calculated for different environments from the thermo-gravimetric data obtained for the samples and they show that corrosion rate is minimum in air when compared to chemical environment. The scale formed on the samples upon hot corrosion was characterized by using X-ray diffraction (XRD), SEM, and EDAX analysis to understand the degradation mechanisms.     

Fractographic and microstructural analysis of fatigue crack growth in a Ti-6Al-4V fan disc forging

The constant amplitude fatigue crack growth behaviour of a conventionally (+β) solution treated and aged Ti-6Al-4V fan disc forging was examined by fractographic and microstructural analysis. The crack growth process was complex with many interrelated fracture features. A transition in the fatigue crack growth curve correlated with a change from structure-sensitive to continuum-mode crack growth, primarily in the transformed and aged β grains, and a decrease in fracture surface roughness. The transition was probably caused by the cyclic plastic zone size becoming equal to and exceeding the average platelet packet size. The significance of such transitions for prediction of fatigue crack growth and service failure analysis is discussed.     

Effect of Triple Annealing Treatment on Stress Relaxation of Ti-6Al-4V Alloy

The effect of triple annealing on stress relaxation of Ti-6Al-4V alloy as well as the microstructure after stress relaxation werestudied. The results showed that triple annealing treatment enhanced the resistance of stress relaxation performance, andwhen the temperature was rising, this effect became notable. The stress relaxation deformation mechanism is of dislocationcreep at 400℃ and recovery creep at 600℃.     

Hydrogen Treatment of Cast Ti-6Al-4V Alloy

This paper presents the results of an investiga-tion of the effect of hydrogen treatment onmicrostructures and tensile and low cycle fatigueproperties of a Ti-6Al-4V cast alloy.The phasetransformation and the refining mechanism of thecast microstructure during the process of hydrogentreatment were studied.It was found that afterhydrogen treatment,the coarse Widmanstttenstructure of the as-cast Ti alloy was transformedinto a very fine and equiaxed α+β microstructurewithout any GBα phase.The tensile strength andductility and the low cycle fatigue life of thehydrogen treated specimens were significantly im-proved.     

Laser Surface Modification of Ti-6Al-4V with Addition of Pr

The behaviour of oxidation at elevated tem-peratures and fretting in the laser-alloyed layer ofTi-6Al-4V with the addition of Pr was studied.The results show that the addition of Pr changes thestructure of oxide scale of Ti-6Al-4V,controls theshort-range diffusion of oxygen to thescale/substrate interface and increases the adhe-sion and ductility of the scale,thus changing theoxidation kinetics and considerably reducingoxidation rate.The analysis of fretting test showsthat the existence of high hardness layer in the al-loyed zone,fine dendrites perpendicular to the sur-face of the high hardness layer and the oxide scaleproduced during fretting at elevated temperaturesare all beneficial to the improvement of wear resist-ance.     

Ti-6Al-4V等离子弧焊对接板超塑胀形特性研究

通过自由胀形实验研究了等离子弧焊对接板的超塑胀形性能及影响因素．结果表明等离子弧焊对接板具有良好的超塑胀形性能，其极限胀形高度可超过凹模半径．在胀形过程中，焊缝组织发展成球状α 长条状α组织．焊缝和基体间存在变形不均匀性．在同样的胀形条件下，胀形气压有—最佳数值，气压过大或过小均降低极限胀形高度．最后给出了一个应用等离子弧焊对接板进行超塑胀形的实例．     

Ti-6Al-4V合金包覆叠轧薄板的加工工艺与组织性能研究

研究了包覆叠轧加工及热处理工艺对Ti-6Al-4V合金室温拉伸及疲劳性能的影响规律,观察分析了不同状态下组织形貌的特征及变化情况.结果表明,单向热轧工艺有利于提高合金薄板的延伸率,但对疲劳性能则会产生不利影响,而交叉换向热轧工艺则有利于板材获得较好的综合性能.     

Study on the flow properties of Ti-6Al-4V powders prepared by radio-frequency plasma spheroidization

Spherical Ti-6Al-4V powders were prepared using radio-frequency plasma spheroidization. A laser particle size analyser, a scanning electron microscope, an X-ray diffractometer and a Freeman FT4 powder rheometer were used to analyse the granulometric parameters, micro-morphologies, phase constitutions and flow properties of the raw and the spheroidized powders, respectively. The spheroidized powders exhibited an almost 100% degree of sphericity, smooth surfaces, favourable dispersion and narrow particle size distribution under appropriate plasma technological parameters. The average particle size of the spheroidized powders increased slightly as compared with that of the raw powders. In addition, the spheroidized powders exhibited higher conditioned bulk density and improved flow properties (including the dynamic flow properties, aeration, compressibility, permeability and shear properties) as compared with those of the raw powders.     

基于BP神经网络L-M优化算法的Ti-6Al-4V电火花线切割工艺参数优化

针对机械切削性能差、难加工的Ti-6Al-4V合金,运用正交试验法进行了电火花线切割加工工艺试验研究。探讨了电火花线切割加工的规律和特性,分析了脉冲宽度、脉冲间隔、功放管数和运丝速度等工艺参数对Ti-6Al-4V加工质量的影响,得到了线切割加工最优化参数组合。借助L-M优化算法的BP神经网络搭建了线切割加工工艺网络预测模型,该模型预测精度较高,可为钛合金高质量切割提供可靠的工艺参数预测,对Ti-6Al-4V的实际生产加工具有一定的参考作用。     

Antibacterial Properties of Ti-6Al-4V-xCu Alloys

Surgical implant-associated bacterial infection is becoming a serious clinical problem.A series of copper-bearing titanium alloy,Ti—6AI—4V—xCu(x = 1,3,5 wt%),were fabricated in the present study in order to reduce the hazard of the bacterial infection problem by means of the strong antibacterial ability of Cu element.The metallography,X-ray diffraction,antibacterial ability,corrosion resistance and cytotoxicity of Ti—6AI—4V—xCu alloys were preliminarily studied with comparison to the commercial medical Ti—6AI—4V alloy.The Ti—6AI—4V—xCu alloys showed obvious antibacterial abilities with good corrosion resistance and cytocompatibility,and the antibacterial role was enhanced with increasing Cu content,which has significant potential for clinical applications as surgical implant materials.     

Superplastic Forming and Diffusion Bonding for Sandwich Structure of Ti-6Al-4V Alloy

Superplastic forming and diffusion bonding (SPF/DB) is a well-established process for the manufacture of components almost exclusively from Ti-6AI-4V sheet material. The sandwich structure of Ti-6AI-4V alloy is investigated. The effects of the microstructure on the SPF/DB process were discussed. The microstructure at the interfaces and the distribution of thickness were researched.