TA15 Titanium Alloy Research Articles

Microstructure and dry sliding wear resistance of laser clad TiC reinforced Ti–Ni–Si intermetallic composite coating

Wear resistant TiC reinforced Ti–Ni–Si intermetallic composite coating with a microstructure consisting of TiC uniformly distributed in Ti 2Ni 3Si–NiTi–Ti 2Ni multi-phase intermetallic matrix was fabricated on a substrate of TA15 titanium alloy by the laser cladding process using TiC/Ti–Ni–Si alloy powders as the precursor materials. Microstructure of the coating was characterized by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray energy dispersive spectrometer (EDS). Dry sliding wear resistance of the laser clad TiC reinforced Ti–Ni–Si intermetallic composite coating was evaluated at room temperature. Results indicated that the TiC/(Ti 2Ni 3Si–NiTi–Ti 2Ni) intermetallic composite coating exhibited excellent abrasive and adhesive wear resistance.

Grinding Force and Surface Integrity on Dry Belt Grinding of TA15 Titanium Alloys

This paper was dedicated to elucidate an investigation of grinding force and workpiece surface of Titanium alloy TA15 in dry grinding by using zirconia alumina belts. The grinding forces were measured by KISTLER 9265B dynamometer. Machined surface morphology and the metallographic structure were observed using 3D viewer microscope. Surface roughness was measured using Mahr Perthometer M1 instrument. The surface microhardness for ground surface was detected by HVS-1000 instrument. The good results were obtained, as follows: low surface roughness, high surface hardness, no microstructural damage, in the form cracks or recrystallisation of the grinding surface, the stable grinding performance with zirconia alumina belts, the small plastic deformation depth of workpiece surface (≤5μm). Therefore belt grinding showed excellent performance during grinding titanium alloy.

Microstructure and mechanical properties of TA15 titanium alloy under multi-step local loading forming

In this paper six different local loading processes were proposed to study the effects of local loading conditions (temperature, deformation degree, loading pass, heats, cooling modes and heat treatment) on the microstructure and mechanical properties of TA15 titanium alloy workpieces including room and high temperature tensile properties, impact property, fracture toughness and high temperature duration property. It is found that it is better to finish the local loading forming in one heating time, if multi-fire forging needed the optimal forging technique as follows: adopting conventional forging (950 °C) at first and then following near-beta forging to control the proportion of the equiaxed primary α phase and the transformed β phase, allocating deformation degree of each loading pass rationally and using WQ cooling mode. Thus the workpiece with good compositive mechanical properties can be obtained.

Analysis on Process and Forming Defects of Large-Scale Complex Integral Component Isothermal Local Loading

Isothermal local loading forming is an advanced technology for large-scale complex integral component forming, but the process is with coupling effects of multi-fields and multi-factors due to the local loading mode and high temperature condition, thus makes deformation mechanism extremely complicated and some forming defects may occur. Based on DEFORM3D software, relative FE models for the isothermal local loading forming of large-scale complex integral components of TA15 titanium alloy have been established, and key technologies for modeling have been dealt with properly. Then taking a representative large-scale complex integral component as object the froming process, the typical deformation behavior and metal flow were investigated. And typical forming defects which may occur during the process and causes for them are discussed.

Microstructure characteristics and mechanical properties of laser–TIG hybrid welding joint of TA15 titanium alloy

The laser–tungsten inert gas (TIG) hybrid welding technique is used to weld TA15 titanium alloys. The microstructure and mechanical properties of the welded joint are then analysed systematically. The results indicate that the laser beam can centralise the energy of TIG arc and increase the penetration of weld seam. There are columnar crystals on the top of the weld seam and equiaxed crystals at the bottom. By the way of element analysis, it is found that the major elements, such as Ti, Al, Mo and V, distribute uniformly in the weld seam. Besides, the tensile strength of hybrid welding joint achieves 98% of that of base metal and the fracture of samples proves to be a gliding fracture. The TA15 titanium alloy is joined successfully by laser–TIG hybrid welding in this experiment.

Effect of high-density electropulsing on microstructure and mechanical properties of cold-rolled TA15 titanium alloy sheet

The specimens cut from the cold-rolled TA15 titanium alloy sheet at 0°, 45° and 90° to the rolling direction are treated by high-density electropulsing (maximum current density Jmax = 4.8–5.4 × 103 A/mm2, period tp = 110 μs). The mechanical properties before and after the electropulsing treatment are examined by using uniaxial tensile test. The morphologies of the microstructure and the fracture surface of the cold-rolled and the electropulsed specimens are observed using optical microscopy (OM) and scanning electron microscopy (SEM). The experimental results indicate that the electropulsing treatment gave a significant increase in total elongation of TA15 sheet. The difference of the mechanical properties between the 0°, 45° and 90° direction specimens is almost diminished. The research results show a remarkable advantage of the electropulsing treatment for cold-rolled TA15 sheet. The mechanism of the microstructure evolution under electropulsing is discussed.

Effect of spinning deformation on microstructure evolution and mechanical property of TA15 titanium alloy

Hot spinning of tubular workpiece of TA15 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 TA15 alloy could be improved by annealing at the temperature no higher than recrystallization temperature with slight decrease of tensile strength.

The Influences of Cutting Speed on the Fatigue of Titanium Alloy

This research is concerned with the influences of cutting speed on the fatigue properties of high speed milled Ti-6.5Al-2Zr-1Mo-1V (TA15) titanium alloy. Four different cutting speeds ranging from 50 to 200m/min were used to mill the specimens for fatigue test, and the fatigue properties of them were studied at two stress levels: 80—800MPa and 90—900MPa. The fatigue lives of the specimens milled under different cutting speeds were compared. The fracture surfaces were analyzed using scanning electron microscope (SEM), and cyclic stress-strain properties of TA15 titanium alloy were investigated with a stress-strain gauge. The results showed that increasing cutting speed can help to improve the fatigue properties of titanium alloy, especially at a relatively low cyclic stress level.

The Effect of Isothermal Forging Process Parameters on the Microstructure and the Properties of TA15 Near α Titanium Alloy

In this paper the effect of isothermal forging process parameters on the microstructure and the mechanical properties of TA15 titanium alloy was researched. The results of the tests indicate that, in the range of temperature of 850 °C~980 °C and deformation degree of 20%~60%, with the increase of temperature or deformation, as the reinforcement of deformation recrystallization, the primary α-phase tends to the spherical shape and secondary α-phase transforms from the acicular shape to fine and spherical shape with disperse distribution, which enhance the tensile properties at room and high temperature. With the increment of forging times, the spheroidization of primary α-phase aggrandizes and secondary α-phase transforms from spherical and acicular shape to wide strip shape, which decrease the tensile properties at room and high temperature. The preferable isothermal forging process parameters are temperature of 980 °C, deformation degree of 60%, and few forging times.

Quantitative Characterization of Microstructure of Thermal Deformed TA15 Titanium Alloy by EBSD

Quantitative Characterization of Microstructure of Thermal Deformed TA15 Titanium Alloy by EBSD

Research on the microstructure and properties of weld repairs in TA15 titanium alloy

This paper presents repeated weld repairs of TA15 titanium alloy rolled plates using gas tungsten arc welding with filler metal. The purpose of this work is to examine and quantify the effects of repeated repair cycles of TA15 titanium alloy plates on the microstructure features, elemental distribution, phase composition and mechanical properties. The results demonstrated that sound joints without defects could be obtained after weld repairs. With increasing repair cycles the amount of the acicular α phase in the weld seam increased, the size became larger and the alloy elements were distributed more unevenly between the weld seam and base metal. The hardness and fatigue properties of the joints decreased with increasing repair cycles, especially for the joint after the fourth welding repair.

Research on low cycle fatigue properties of TA15 titanium alloy based on reliability theory

This paper introduces a method to determine the symmetric cycle fatigue limit of TA15 alloy at given confidence γ and survival probability P. It gives a general method to calculate the true survival probability of this material fatigue limit. The median and data of the LCF at γ = 95% and P = 99.9% are acquired after studying the LCF properties of aircraft construction material TA15 at the temperature of 25 and 250 °C. The strain–life curve, cyclic stress–strain curve and parameters of LCF are also achieved. These provide reference to analyze the reliability of aircraft construction and estimate the life.

Hot compressive deformation behaviour and microstructural variation of TA15 titanium alloy

Elevated temperature compressive deformation behaviour of TA15 titanium alloy was investigated at temperatures from 1023 to 1273 K and strain rates from 10−3 to 1 s−1. It was found that the flow stresses of the TA15 alloy dropped with increasing deformation temperature and decreasing strain rate. The microstructure of TA15 alloy was observed and analysed using optical microscope. The volume fraction and the shape of primary alpha phase are influenced by deformation temperature and strain rate.

Macroscopic and microscopic subdivison of a cold–rolled aluminium single crystal of cubic orientation

An aluminium single crystal of cube orientation has been rolled to 15, 30 and 50% reductions under controlled homogeneous rolling conditions. The deformation structure of the rolled specimens was investigated by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) over several scales of magnification. The local crystallographic orientations have been measured by an automatic electron back scattering patterns (EBSP) technique and a semiautomatic TEM method. Orientation image maps based on the local orientation data have been used to reveal the evolution of the deformation structure during rolling. It is observed that by an opposite rotation around transverse direction (TD) the crystal was subdivided into four macroscopic bands, termed matrix bands in the present paper, which are parallel to the rolling plane. Between the four bands there are three transition bands in which the orientation changes continuously from that of a matrix band to that of the adjoining one. A model based on the idea of location–dependent shear strain caused by geometric and friction effects together with a plasticity analysis has been used to explain the macroscopic subdivision of the crystal. In addition to the macroscopic subdivision, a microscopic subdivision by the formation of cell–blocks within the matrix bands and a cell structure within transition bands has also been observed. A difference related to shear amplitude difference between the active slip systems changing continuously across the crystal has been observed. Both the macroscopic orientation of the dislocation boundaries and the misorientation angles and axes across dislocation boundaries are analysed and it is found that Frank9s formula is a useful tool in analysing the dislocation boundaries formed during deformation.