Effect of Concurrent Microstructure Evolution and Hydrogen Level on Flow Behavior of Near Alpha Ti-Alloy
03 Feb 2016-pp 665-672
TL;DR: In this paper, the effect of H on the microstructure and flow properties of compression samples of VT20 Ti-alloy Ti-5.9Al-2.1Zr-1.4Mo was examined.
Abstract: Separate compression samples of VT20 Ti-alloy Ti-5.9Al-2.1Zr-1.6V-1.4Mo (wt%), charged with 0, 0.15 and 0.36 wt%H, were deformed to true strain of 0.70 at a strain rates of 1×10−3 and 1×10−1 s−1 at test temperatures of 600 and 850 °C. H charging led to the varying microstructures ranging from equiaxed to lamellar ones depending on H level. In the course of deformation, their occurred refinement of microstructures with reduced interlamellar spacing depending on the test conditions. The contributions of these sources to microstructure evolution and flow properties were examined in an attempt to explore some correlation between them. An attempt is made to understand the effect of H present on the microstructure and flow properties to account for the variations in the parameters of the constitutive relationship.
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15 Mar 1998-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the thermomechanical processing of beta titanium alloys in general and high temperature deformation mechanisms, microstructure control during TMP, and final mechanical properties in particular are reviewed.
Abstract: Thermomechanical processing (TMP) is associated with two major requirements: (i) to produce usable shapes through primary working (ingot breakdown) and secondary mill operations (hot rolling or forging) and (ii) to optimize mechanical properties through microstructure control during the different stages of the thermomechanical process. This paper reviews the thermomechanical processing of beta titanium alloys in general and high temperature deformation mechanisms, microstructure control during TMP, and final mechanical properties in particular.
620 citations
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TL;DR: In this article, the status of the methods and applications of thermohydrogen processing to titanium alloys are reviewed. And the principles of thermodynamic processing, based on the hydrogen induced alterations of the phase compositions and the kinetics of phase reactions in hydrogenated Titanium alloys, are overviewed.
Abstract: Thermohydrogen processing is a technique in which hydrogen is used as a temporary alloying element in titanium alloys to control the microstructure and improve the final mechanical properties. Thermohydrogen processing can also be used to enhance the processability/fabricability of titanium products including sintering, compaction, machining, and hot working (forging, rolling, superplastic forming, etc.). In the case of near net shapes, such as castings and powder metallurgy products, thermohydrogen processing is the only method available for significant microstructural modifications and consequent enhancement in mechanical properties. This paper reviews the status of the methods and applications of thermohydrogen processing to titanium alloys. Principles of thermohydrogen processing, based on the hydrogen induced alterations of the phase compositions and the kinetics of phase reactions in hydrogenated titanium alloys, are overviewed. Stable and metastable phase diagrams of several titanium alloys...
196 citations
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TL;DR: In this article, a hot compression test on samples of the TC11 (Ti-6.5Al, 3.5Mo, 1.5Zr, 0.3Si) alloy has been done within the temperatures of 750-950°C and strain rate ranges of 0.1-10−s−1 to 40-60% height reduction.
Abstract: Hot compression tests on samples of the TC11 (Ti–6.5Al–3.5Mo–1.5Zr–0.3Si) titanium alloy have been done within the temperatures of 750–950 °C and strain rate ranges of 0.1–10 s−1 to 40–60% height reduction. The experimental results show that the flow stress behavior can be described by an exponential law for the deformation conditions. The hot deformation activation energy (Q) derived from the experimental data is 538 kJ mol−1 with a strain rate sensitivity exponent (m) of 0.107. Optical microstructure evidence shows that dynamic recrystallization (DRX) takes place during the deformation process. Moreover, only α DRX grains are founded in the titanium alloys. The influences of hot working parameters on the flow stress behavior and microstructural features of TC11 alloy, especially on the type of phase present, the morphologies of the α phase, grain size and DRX are analyzed. The optimum parameters for hot working of TC11 alloy are developed.
104 citations
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TL;DR: In this paper, the interaction of hydrogen with titanium was studied in order to characterize some important microscopic and macroscopic properties of this system, such as the variation of the electronic density and the induced density of states due to the presence of the hydrogen in the matrix of Ti.
Abstract: We study the interaction of hydrogen with titanium in order to characterize some important microscopic and macroscopic properties of this system. It is technologically important because, among other applications, the Ti–H system is used as structural material in many applications due to the combination of two important mechanical properties, which are resistance to the corrosion and hardness. Using a calculus program based on the jellium model for the material, we obtain values of properties that are important in the determination of the macroscopic behaviour of the Ti–H system, such as the variation of the electronic density and of the induced density of states due to the presence of the hydrogen in the matrix of Ti. From an experimental point of view, we hydride a titanium matrix in order to determine the effects of the process on the properties of the material structure. The general features of these theoretical and experimental methods are discussed and the corresponding results are compared with experimental data.
35 citations
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TL;DR: In this article, the influence of hydrogen on microstructure evolution and superplastic behavior of a new near α high-temperature titanium alloy-Ti600 alloy was studied.
Abstract: The influence of hydrogen on microstructure evolution and superplastic behavior of a new near α high-temperature titanium alloy-Ti600 alloy were studied. The results show that hydrogen increases the amount of β phase and δ hydride with fcc structure exists in the specimens when the hydrogen content is over 0.3 wt.%. After hydrogenation, the deformation temperature of Ti600 alloy can be decreased about 80 °C and the strain rate can be increased by at least one order. Addition of proper hydrogen can reduce the flow stress of Ti600 alloy significantly. The flow stress of Ti600–0.5H alloy decreases about 78% of that unhydrogenated Ti600 alloy at 840 °C and 5 × 10 −4 s −1 . Moreover, introducing hydrogen into Ti600 alloy decreases the dislocation density, promotes the dislocation motion and facilitates the β phase flow.
31 citations