Optimization of the Ti–0.2Pd alloy properties through heat treatments (original) (raw)
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The effect of heat treatment conditions on the microstructure, phase transformation and mechanical properties of Bi-modal titanium alloy was investigated. The heat treatment process comprises of solution treated at various temperatures of 640, 680, 720 and 760 C for 30 min followed by water quenching and aged at 500 C for 30 min then air cooling. This study was carried out using X-ray diffraction analysis (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), differential thermal analysis (DTA), compression universal testing machine and Vickers hardness tester. The results show that the microstructure of investigated alloys consists of phase, as a matrix, primary phase, small precipitates of secondary phase in addition to orthorhombic martensite ( ") phase found only in the solutionized samples at 720 and 760 C. Transus temperature for the phase found to be around 865 C at heating rate of 10 C/min. The / phase zone is ranging from 650 to 865 C at the same heating rate for all samples. The formation temperature of nanometer α phase and/or disappearing of iso phase are almost constant at 385 °C. The formation of primary α phase was detected at a temperature more than 400 C. Hardness measurements increased as the solution temperature increase. The highest ultimate compression strength, 2680 MPa, achieved with solution temperature of 680 °C. However the maximum yield stress, 1725 MPa, obtained with 760 C solution temperature. The highest contraction was attained with the solutionized sample at 640 C for 30 min.
Phase transformations in TiV alloys
Journal of Materials Science, 1983
The morphology and substructure of the athermal martensite produced byβ-quenching Ti, Ti-5% V and Ti-10% V have been described in detail. The martensitic transformation in the Ti-10% V alloy was found to be incomplete leading to a structure comprised of theμ-,β- andω-phases. The extent ofβ retention increases with the V content of the alloy and the martensitic transformation was completely inhibited on quenching a Ti-20% V alloy to room temperature. This alloy was found to undergo a stress-induced martensitic transformation. The morphology and crystallography of the stress-induced products have been examined in detail.
IOP Conference Series: Materials Science and Engineering, 2018
In the present study, the microstructures of five samples of the Ti-6246 alloy were investigated using SEM and OM devices. Four samples had been examined during different thermo-mechanical processing and heat treatment (hot plastic deformation and normalizing heat treatment) in α + β and β field domain respectively. The results demonstrate that the phase transformations and compositional modifications induced by thermo-mechanical processing and heat treatment have a dramatic influence on the microstructural characteristics. It was concluded that all samples present many morphologies textures and orientations. The microstructures features had improved in the normalizing heat process in comparison with the parent material and the hot deformation process.
MDPI, 2020
The present study investigates the influence of hot-deformation, above β-transus and different thermal treatments on the microstructural and mechanical behaviour of a commercially available Ti-6246 titanium-based alloy, by SEM (scanning electron microscopy), tensile and microhardness testing techniques. The as-received Ti-6246 alloy was hot-deformed-HR by rolling, at 1000 • C, with a total thickness reduction (total deformation degree) of 65%, in 4 rolling passes. After HR, different thermal (solution-ST and ageing-A) treatments were applied in order to induce changes in the alloy's microstructure and mechanical behaviour. The applied solution treatments (ST) were performed at temperatures below and above β-transus (α → β transition temperature; approx. 935 • C), to 800 • C, 900 • C and 1000 • C respectively, while ageing treatment at a fixed temperature of 600 • C. The STs duration was fixed at 27 min while A duration at 6 h. Microstructural characteristics of all thermomechanical (TM) processed samples and obtained mechanical properties were analysed and correlated with the TM processing conditions. The microstructure analysis shows that the applied TM processing route influences the morphology of the alloy's constituent phases. The initial AR microstructure shows typical Widmanstätten/basket-weave-type grains which, after HR, are heavily deformed along the rolling direction. The STs induced the regeneration of α-Ti and β-Ti phases, as thin alternate lamellae/plate-like structures, showing preferred spatial orientation. Also, the STs induced the formation of α-Ti/α"-Ti martensite phases within parent α-Ti/β-Ti phases. The ageing treatment (A) induces reversion of α-Ti/α"-Ti martensite phases in parent α-Ti/β-Ti phases. Mechanical behaviour showed that both strength and ductility properties are influenced, also, by applied TM processing route, optimum properties being obtained for a ST temperature of 900 • C followed by ageing (ST2 + A state), when both strength and ductility properties are at their maximum (σ UTS = 1279 ± 15 MPa, σ 0.2 = 1161 ± 14 MPa, ε f = 10.1 ± 1.3%).
Martensitic transformation of Ti50Ni30Cu20 alloy prepared by powder metallurgy
Journal of Alloys and Compounds, 2011
Phase transformation behavior of Ti50Ni30Cu20 shape memory alloys prepared by powder metallurgy is analyzed with respect to the duration of mechanical alloying. The processed blends were studied by differential scanning calorimetry and room temperature X-ray diffraction. The martensitic transformations evidenced by thermal scans are discussed in correlation with the relative phase content obtained from the refinement of the X-ray diffraction patterns.
Strain-induced phase transformation during thermo-mechanical processing of titanium alloys
Materials Science and Engineering: A, 2012
Strain-induced phase transformation studies have been conducted in a Ti-6Al-2Sn-4Zr-6Mo alloy. This alloy was subjected to b sub-transus deformation upon slow cooling from the b-phase field and the effect of strain on the extent and morphology of the phase transformation during hot-deformation was determined. In addition, the transformation kinetics and the morphology of the newly formed a-phase were studied following deformation under different cooling conditions. By applying strain, the rate of the b-to-a phase transformation increased significantly during deformation as well as during slow cooling following deformation. This increase in the kinetics of the b-to-a transformation can be ascribed to straininduced phase transformation. Also, the extent of deformation of the b-phase had a marked effect on the resulting morphology and size of the newly formed a-phase. Transformation of un-deformed b-phase rendered a-phase of acicular morphology only. However, following deformation of the b-phase, acicular as well as globular a-phase morphologies have been observed upon cooling.
IJERT-Microstructure and Mechanical Properties of Heat Treated Ti8Al1Mo1V Alloy
International Journal of Engineering Research and Technology (IJERT), 2021
https://www.ijert.org/microstructure-and-mechanical-properties-of-heat-treated-ti8al1mo1v-alloy https://www.ijert.org/research/microstructure-and-mechanical-properties-of-heat-treated-ti8al1mo1v-alloy-IJERTV10IS040248.pdf Titanium and its alloys exhibit several unique properties and have been widely used in the field of chemical industry, aviation, aerospace, marine and medical devices since 1950.Titanium and titanium alloys are widely used in aerospace field due to property of high strength to weight ratio as it saves lot of cost spent on fuel due to weight and non reactivity to adverse environmental conditions. The applications of Ti8Al1Mo1V include compressor blades, turbine discs, housing inner skin and frame for nozzle assembly of Jet engines. Literature review indicates that published information not available regarding systematic reporting of structure and properties of this alloy. Hence in this study systematically studies have been carried out on structure and properties of Ti-8Al-1Mo-1V alloy when subjected to solutionising and ageing followed by air cooling and thermal oxidation heat treatments. In this study Titanium alloy Ti8Al1Mo1V (TA8DV) is subjected to solutionising and ageing followed by air cooling and further subjected to thermal oxidation at 600°C, 750°C and 900°C for 6 hours, 15 hours and 24 Hours time duration in each combination in a resistance furnace in presence of Air. The thermal oxidized samples are subjected to Tensile test, Micro hardness test and the cross sectioned samples are tested for microstructure in an optical microscope. Micro hardness (knoop hardness number) is more at the surface and reduces gradually to core. The maximum number achieved is 548.8 for sample To-24-900; it is revealed that the hardness increases with temperature and time duration. From Microstructure studies the effect of thermal oxidation varies from15 microns at 6 hrs duration 600°C and 150 microns at 24 hours duration 900°C temperature and it is known that the effect of oxidation varies proportional to temperature and time duration. From tensile test the yield strength and ultimate tensile strength decreases from 8% to 15 % as compared to the value of the sample in ASR condition. 1. INTRODUCTION: Titanium is the 4 th abundant structural metal available on earth crust after aluminum, iron and magnesium. Titanium element was discovered in 1791. There are two allotropic forms of titanium: α-Ti at 882.5°C or lower, with a closely packed hexagonal (hcp) lattice structure and β-Ti at 882.5°C or higher with a body centered cubic (bcc) lattice structure. Depending on the phase structure and the content of β stable element, titanium alloy is classified in to three categories: α, α+β and β. There are varieties of Titanium alloys available depending on the composition some of the alloys are Ti6Al4V, Ti8Al1Mo1V, Ti6Al2Sn4Zr2Mo, Ti10V3Fe3Al etc. Depending on the phases formed the alloys are classified as α, α+β, β titanium alloy. Titanium and its alloys exhibit several unique properties and have been widely used in the field of chemical industry, aviation, aerospace, marine and medical devices since 1950. [1]. Main physical properties of titanium and titanium alloys include: Low density and high specific strength: the density of Ti is 4.51 g/cm3 with tensile strength up to 1300MPa. The specific strength is much higher than that of aluminum and alloying steel. Good heat resistance: some new types of titanium alloys can be used for a long time at 600°C or higher, and are suitable for the aviation and aerospace heat-resistance components; Good low temperature resistance: at temperature of-196 to-253°C, titanium maintains relatively good ductility and toughness. These make Ti to be an ideal material for cryogenic vessels and tank equipments; Good corrosion resistance: Ti is very stable among many media. For example, Ti is corrosion resistant in the medium of oxidation, neutral and weak reduction. However titanium also has some drawbacks along with aforementioned advantages which are Low wear resistance: the low surface hardness of titanium makes the adhesive wear easy to occur. Low oxidation resistance at high temperature: titanium shows a strong tendency of oxidation at a temperature of 350°C or higher. High cost: the price of titanium is 5-10 times higher than that of steel. [1]. Ti8Al1Mo1V is considered which comes under near α alloy, which was initially developed as super alloy for engine use principally as forgings. Ti8Al1Mo1V alloy contains a relatively large amount of alpha stabilizer, aluminum and Fairley small amounts of beta stabilizers, molybdenum and vanadium (plus iron as impurity). Although this alloy is metallurgically an alpha-beta alloy, the small amount of beta stabilizer in this grade(1Mo+1V) permits only small amounts of the beta phase to be stabilized, thus the alloy is also known as near alpha alloy. Although this is a near alpha alloy, an increase in tensile strength by almost 25% over that of mill annealed material can be obtained by appropriate choice of heat treatment sequence consisting of quenching followed by an ageing treatment.[9]. The yield strength, the ultimate tensile strength and the elongation depend strongly on the solutionising temperature [10]. Many non metallic elements are used to enhance the titanium alloy surface to improve its Tribological properties, which can form a hardened, interstitially enriched alpha-case layer with or without an outer surface layer of hard compound. [7]. The thermal oxidation process is one of the most important advances in the field of surface engineering of Ti-based materials due to its capability of enhancing the Tribological properties of Ti alloys [1]. Ti-6Al-4V alloy treated using thermal oxidation exhibited low coefficient of friction and low wear rate, which is attributed to both the formation of a useful oxide and hardened diffusion layer. Many non metallic elements are used to enhance the titanium alloy surface to improve its
High temperature compression deformation studies of Ti-6Al-2Zr-1Mo-1V titanium alloy in full  phase region with different strains/strain rates and then with subsequent varied cooling rates were performed to understand the microstructure evolution. Crystal orientation information and microstructure morphology of all tested samples were investigated by electron backscatter diffraction (EBSD) measurements. The crystal orientations of prior high temperature  grains were estimated by reconstructing the retained  phase at room temperature. The theoretical crystal orientations of all possible ␣ variants within an investigated prior  grain were calculated according to the Burgers orientation relationship (OR) between parent and product phase. The calculated and experimental results were then compared and analyzed. The influences of deformation strain, strain rate and cooling rate on the Burgers OR between prior  matrix and precipitated ␣ phase were investigated. Full discussions have been conducted by combination of crystal plasticity finite element method (CP-FEM) grain-scale simulation results. The results indicate that external factors (such as deformation strain, strain rate and cooling rate) have a slight influence on the obeying of Burgers OR rule during  → ␣ phase transformation. However, strain rate and cooling rate have a significant effect on the morphology of precipitated ␣ phase.
Materialia, 2019
New theory is presented to describe the occurrence of plasticity-induced transitions in titanium alloys. The approach is able to predict the composition dependence of transformation induced plasticity (TRIP), superelasticity, as well as martensite formation upon quenching. Martensite formation in the absence of stress is considered as the result of a competition between elastic strain energy and chemical driving force. Assuming that the formation of martensite is the result of a thermally activated nucleation process followed by athermal growth, a nucleation parameter is postulated to describe the conditions under which martensite is formed upon quenching; the parameter accounts for the ratio between the available thermal energy and an energy barrier for nucleation, suggesting that phase is not the main factor controlling martensite inhibition. This nucleation parameter is able to describe, for the first time, martensite occurrence in 130 alloys from the literature, quantifying the martensite start temperature (M s) reported for 49 alloys with great precision. An empirical parameter ([Fe] eq) is proposed and, when combined with the M s prediction, it allows to define regions within which TRIP and superelasticity occur. By defining threshold values for the M s , the [Fe] eq and the nucleation parameter, candidate alloys likely to display TRIP, superelasticity or martensitic transformation upon quenching can be identified. As a result, this method can be adopted to design alloys with tailored plasticity behaviour.