Properties of Ni–Cr–Al Alloys Obtained by a Powder Metallurgy Method

Alloys of practically 100% density were formed by hot pressing mixtures of nickel, chromium and aluminum powders. The principal phases formed are solid solutions based on chromium, on nickel, and also the intermetallic NiAl. These correspond to phases in the phase equilibrium diagram of theNi Cr Al system. The strength and wear resistance of the alloys are determined by the ratio of phase components.     

Dry Sliding Wear Behaviour of Ti–6Al–4V Alloy Consisting of Bimodal Microstructure

In the present paper, dry sliding wear behaviour of Ti–6Al–4V titanium alloy consisting of bimodal microstructure sliding against EN-31 steel at different sliding velocities (0.3, 0.6 and 0.9 m/s) and applied loads (60, 80 and 100 N) has been studied using a multiple Tribo tester and the results are presented. Two wear mechanisms have been identified irrespective of the applied load: oxidative wear occurs at the lowest sliding velocities and delamination wear occurs at the highest. Results indicated that by increasing the sliding velocity a transition from oxidative wear to delamination wear occurs with a corresponding minimum in the loss of volume due to wear. These results have been described by the analysis of the wear debris and that of the worn specimens using XRD, optical microscopy, FESEM and interpreted based on the metallurgical characteristics of titanium alloys which influence the wear resistance.     

Fatigue strength of a Ti–6Al–4V alloy produced by selective laser melting

The fatigue properties and the fracture mechanisms of the Ti–6Al–4V alloy produced by selective laser melting (SLM) from a powder of an CL41TiELI titanium alloy have been studied. Cylindrical blanks were grown at angles of 90° and 45° to a platform. The best fatigue strength is observed in the samples the blanks of which were grown at an angle of 45°. It is found that the structure of the SLM material can contain portions with unmelted powder particles, which are the places of initiation of fatigue cracks.     

Strength–Ductility Property Maps of Powder Metallurgy (PM) Ti-6Al-4V Alloy: A Critical Review of Processing-Structure-Property Relationships

Metallurgical and Materials Transactions A - A comprehensive assessment of tensile properties of powder metallurgical (PM) processed Ti-6Al-4V alloy, through the mapping of strength–ductility...     

Laser Additive Manufactured Ti–6Al–4V Alloy: Heat Treatment Studies

The effect of heat treatment on microstructure and mechanical behaviours of direct metal laser sintered Ti–6Al–4V samples have been studied. Rectangular parts were built in two different directions; vertical and horizontal and subjected to two different heat treatment cycles: above β transus and below β transus with air cooling. Surface characteristics, microstructural examination and mechanical properties have been investigated. Below β transus treatment creates a modification in the surface morphology with a fine dimple network. Above β transus treatment leads to extensive grain growth at the middle section of the vertically build component thereby increasing its microhardness. Both the selected heat treatment cycles significantly reduces the tensile strength and improves the elongation when compared to as-sintered material. However, below transus temperature treated vertical built specimen results in optimum combination of tensile strength (1124 MPa) and elongation (20%). Higher coefficient of friction has been recorded for specimens after heat treatment.     

Temperature,Stress and Distortion of Ti–6Al–4V Alloy Low-Temperature Friction Stir Welding Assisted by Trailing Intensive Cooling

The low-temperature friction stir welding (FSW) in which peak temperature is lower than the transus temperature of β phase was achieved using rotational speed of 100 rpm and welding speed of 30 mm/min. Trailing intensive cooling with liquid nitrogen was successfully applied to FSW under the low-temperature welding conditions. Comparisons of the temperature field, plastic strain, residual stress and welding distortion between intensive and conventional cooling were investigated by experiment and simulation. Results reveal that trailing intensive cooling is attributed to shrink high-temperature area and reduce the value of peak temperature and plastic strain. Longitudinal residual stress presents M shape, and the reduction of maximum tensile residual stress reaches 4.8%. The welding distortion shows an anti-saddle shape, and the decrement of welding distortion in transverse direction is 34.5%.     

Ti—6Al—4V合金加工

Ti-6Al-4V合金是用途最广泛的钛合金，在航空、汽车、能源、舰船、化工、医疗器械及体育用品等所有应用领域中，该合金占到50%以上。在航空业中，Ti-6Al-4V合金用作重要的零部件，从隔板、机翼、机架到压气机盘、发动机、叶片、气瓶。例如，Ti-6Al-4V在美国F22“猛禽”战斗机总重中占36%。因此，对Ti-6Al-4V零部件进行设计并改进热加工工艺有助于大大降低成本。1 Ti-6Al-4V合金的级别Ti-6Al-4V合金根据间隙元素含量被划分成两种级别，它们之间的主要差异是氧含量不同。工业级Ti-6Al-4V中氧的质量分数为0.16%~0.20%；超低间隙(ELI)…     

Physico-Chemical Investigation of Component Interactions of the Si ― Al ― O ― N ― Ti System in the Region Si3N4 ― AlN ― Al2O3 ― SiO2 ― TiN ― TiO2. Part 1. Subsystems Si3N4 ― Al2O3, Si3N4 ― TiN,and Al2O3 ― TiN

Using the methods of differential thermal and x-ray diffraction analysis an investigation was made of component reactions in the Si Al O N Ti system, particularly between the compounds Si ₃N₄ Al₂O₃, Si₃N₄ TiN, and Al₂O TiN under conditions approximating those used in the hot pressing of composites. It was established that in the reaction of Si₃N₄ with Al₂O₃, -sialon, SiO₂, AlN, and the intermediate reaction products (mullite and X-phase) are formed. In the reaction of Si₃N₄ with TiN, as a result of the decomposition of Si₃N₄ at 1650-1900°C titanium disilicide is produced, which forms eutectics with free silicon and residual TiN at 1320 and 1280°C, respectively. The reaction of Al₂O₃ with TiN similarly leads to the formation of a eutectic between Al₂O₃ and spinel at 1850°C. The presence of eutectic liquids in the specimens after sintering promotes densification of the material, and improves certain of its mechanical properties.     

粉末冶金Ti6Al4V合金的研究

采用Ti粉、AlV中间合金粉,通过模压和真空烧结制备了Ti6Al4V合金,并通过随后的锻造和热处理来改变其组织和性能.通过金相显微镜、X射线衍射(XRD)仪、扫描电镜(SEM)及力学性能检测等分析手段,系统研究了压制压力对Ti6Al4V烧结体密度的影响,以及试样状态(烧结态及烧结淬火态)、锻造温度、淬火温度及时效温度等工艺参数对粉末冶金Ti6Al4V合金组织和性能的影响.结果表明:通过模压和烧结可制备出相对密度达97.4%的Ti6Al4V合金;Ti6Al4V烧结态及烧结淬火态合金经过锻造后,相对密度接近100%;通过不同热处理工艺得到不同组织和性能,能获得等轴组织,其α晶粒尺寸在5μm左右.     

Dry Sliding Wear Behavior of Ti–6Al–4V Implant Alloy Subjected to Various Surface Treatments

Titanium alloys are extensively used in various fields of engineering, medicine, aerospace, marine due to their excellent mechanical properties. Their usage is more pronounced today in the field of biomedical implants due to superior biocompatibility, corrosive resistance and high strength. However, titanium alloys have poor wear resistance due to high coefficient of friction. Poor abrasive wear resistance results in the formation of wear debris at the implant area causing toxicity, inflammation and pain. Surface treatment of the implant alloy through heat treatment, application of protective coatings and introduction of compressive residual stresses by shotpeening are some of the methods to mitigate wear of the implant alloy. In this work Ti?C6Al?C4V implant alloy is treated under various conditions of heat treatment and shotpeening operations on a pin on disc wear testing machine. Scanning electron micrograph along with energy dispersive spectrometry analysis is done to authenticate the experimental results obtained during the wear testing procedure.     

Electrochemical Behavior of SLM Ti–6Al–4V Alloy After Long Time of Immersion in Lactic Acid Environment

Metallurgical and Materials Transactions A - The corrosion behavior of selective laser melted Ti–6Al–4V alloy (SLM Ti–6Al–4V) was assessed in 0.1 M lactic acid + 0.1 M NaCl...     

Mechanico-Chemical Synthesis,Structure and Properties of Alloys Based on the System Ti ― Al

The kinetics of structure and phase formation in Ti Al and Ti Al Sc alloy powders in the process of mechano-chemical synthesis from elemental powders was investigated. It was established that the formation of microdimensional x-ray amorphous composite particles with nanodimensional structural components occurs. It was shown that in consolidation of the mechanically alloyed powders by hot isostatic pressing structural heredity is realized, and that the materials produced have unusually high microhardness compared to that of similar cast alloys. This is characteristic of nanostructured materials. In addition to high hardness the materials are characterized by high work of plastic deformation at room temperature. Microalloying the alloy powders with scandium has a complex positive effect on the strength properties of the hot pressed materials, due to the formation of a dispersion hardened microstructure with purified nanodimensional grains.     

Directional Hot Isostatic Pressing of Ti6Al4V–SiC Composite with Elements Prepared by Selective Laser Melting Technology

Metallurgist - The process of directional hot isostatic pressing (HIP) of Ti6Al4V-SiC composite is studied in this work. Samples of locally reinforced titanium alloy Ti6Al4V billet are selected,...     

Ti6Al4V合金热浸铝研究

采用热浸镀法在Ti6Al4V合金表面制备出TiAl3金属间化合物涂层,并在不同温度下对浸镀后的试样进行热扩散处理.通过XRD、SEM等分析手段对涂层结构和成分进行测试分析,探讨涂层形成机理.结果表明:Ti6Al4V合金经750℃ 5 min热浸铝后,在其表面形成了由纯铝和TiAl3组成的涂层,TiAl3合金层厚约1.5 μm;经550℃退火5h后,TiAl3含量增多而纯铝层含量则相应减少,纯铝层几近消失,合金层厚度约为40μm,涂层致密;经930℃退火5h后,表面的涂层转化为单相的TiAl3,产物纯净,但涂层中出现了较多的孔洞,自涂层表面到钛合金基体,孔洞浓度呈梯度变化.     

Enhancement in Strain Hardening on Boron Addition in As-Cast Ti–6Al–4V Alloy

It has been previously reported that the addition of boron to Ti–6Al–4V results in significant refinement of the as-cast microstructure and enhancement in the strain hardening. However, the mechanism for the latter effect has not been adequately studied. The aim of this study was to understand the reasons for the enhancement in room temperature strain hardening on addition of boron to as cast Ti–6Al–4V alloy. A study was conducted on slip transmission using SEM, TEM, optical profilometry and four point probe resistivity measurements on un-deformed and deformed samples of Ti–6Al–4V–xB with five levels of boron. Optical profilometry was used to quantify the magnitude of offsets on slip traces which in turn provided information about the extent of planar or multiple slip. Studies on deformed samples reveal that while lath boundaries appear to easily permit dislocation slip transmission, colony boundaries are potent barriers to slip. From TEM studies it was also observed that while alloys containing lower boron underwent planar slip, deformation was more homogeneous in higher boron alloys due to multiple slip resulting from large number of colony boundaries. Multiple slip is also proposed to be the prime cause of the enhanced strain hardening.