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Investigation Of The Effect Of Microstructure And Texture On The Fatigue Properties And Deformation Modes Of An Alpha Beta Titanium Alloy Ti 6al 2nb 1ta 08mo
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Book Synopsis Investigation of the Effect of Microstructure and Texture on the Fatigue Properties and Deformation Modes of an Alpha + Beta Titanium Alloy, Ti-6Al-2Nb-1Ta-0.8Mo by : Donald Shengduen Shih
Download or read book Investigation of the Effect of Microstructure and Texture on the Fatigue Properties and Deformation Modes of an Alpha + Beta Titanium Alloy, Ti-6Al-2Nb-1Ta-0.8Mo written by Donald Shengduen Shih and published by . This book was released on 1983 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Investigation of the Effects of Microstructure on the Deformation Modes and Mechanical Properties of Ti-6Al-2Cb-1 Ta-0.3 Mo by : E. A. Starke
Download or read book Investigation of the Effects of Microstructure on the Deformation Modes and Mechanical Properties of Ti-6Al-2Cb-1 Ta-0.3 Mo written by E. A. Starke and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Deformation and Texture Evolution of Ti-10V-2Fe-3Al by : Juan Zhao
Download or read book The Deformation and Texture Evolution of Ti-10V-2Fe-3Al written by Juan Zhao and published by . This book was released on 2015 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: Beta titanium alloys form one of the most versatile classes of materials with respect to processing, microstructure, and mechanical properties. Owing to their body centered cubic structure, [beta] titanium alloys offer an attractive alternative to the [alpha]+[beta] and [alpha] alloys as they usually possess higher specific strengths, better heat treat ability, deep hardening properties, and lower processing temperatures. However, beta titanium alloys are very sensitive to deformation parameters and may produce quite different microstructures and further various mechanical properties. It is necessary to explore the effect of deformation parameters on the microstructure evolution, including testing temperature, strain rate and strain.Texture introduced by deformation may produce a strong anisotropy of mechanical and other properties, and can also lead to the localization of these properties. Therefore, in order to make use of the advantages of [beta] titanium alloys, we must also understand the evolution of texture.The aim of this project is to reveal the deformation mechanisms and the evolution of texture during hot deformation in [beta] titanium based on compression tests, optical microscopy (OM), scanning electron microscopy (SEM) and texture evolution by Electron backscattered diffraction (EBSD) and x-ray texture observation.The microstructure, texture and mechanical response of forged Ti-10V-2Fe-3Al plates were investigated. Forged plates of as-received Ti-10V-2Fe-3Al alloy features fine [alpha] phase in large [beta] grains. Yield locus tests were performed which confirmed that [beta] phase {001} 110 texture resulted in lower mechanical anisotropy in the forged plate. The relationship between [alpha] phase and [beta] matrix texture was characterized by EBSD. The Burgers relationship is observed between these two phases in the as-received state, and this is preserved from the forging process and following 760 °C heat treatment. After further heat treatment at 820 °C, both [beta] phase and [alpha] phase form recrystallization textures and the Burgers relationship is no longer obvious. Furthermore, through thickness texture inhomogeneity was studied in the as-received plate. A rotated cube texture is widely spread at the surface, and more intense at quarter thickness and center. At the surface there is a tendency to form the {111} 112 recrystallization texture while in the quarter thickness and center, the restoration mode is mainly recovery.Following solution treatment in single [beta] phase field, deformation in [alpha]+[beta] phase field was performed, which presented a considerable effect on [alpha] phase morphologies. The microstructure of [alpha] phase is basically an evolution of lamellar [alpha] breaking up into shorter lamellar and coarsening into globular morphologies. Dynamic recovery is the main restoration mechanism for [beta] phase. The dominant orientations of beta phase include a strong rotated cube texture and weak 111 orientations parallel to compression direction. The orientation relationship between [alpha] phase and [beta] matrix follows the Burgers relationship and deformation in [alpha]+[beta] phase field does not destroy this orientation relationship.Deformation at above [beta] transus temperature leads to strong 001 and weak 111 textures. With increasing temperature and decreasing strain rate, the 001 texture gets strengthened gradually and 111 orientations show weakening tendency. The volume fractions of dynamic recrystallization are lower than 10% under all the deformation conditions in the single [beta] phase field, showing the main dynamic restoration mechanism is also dynamic recovery at above [beta] transus temperature tested in this thesis. Moreover, deformation parameters show significant effects on microstructure evolution. At low strain rate, dislocation annihilation and dynamic recovery are very effective, resulting in significantly larger subgrain size and less pancaked original grains. Besides dynamic recovery, continuous dynamic recrystallization by progressive lattice rotation is also observed, which occurs at high strain rate and low temperature. Geometric dynamic recrystallization hardly occurs, as HAGB spacing is much larger than the subgrain size at the highest strain of 0.9. Discontinuous dynamic recrystallization is rarely observed in the sing [beta] phase field in Ti-10V-2Fe-3Al.
Book Synopsis Fatigue of Beta Processed and Beta Heat-treated Titanium Alloys by : Russell Wanhill
Download or read book Fatigue of Beta Processed and Beta Heat-treated Titanium Alloys written by Russell Wanhill and published by Springer Science & Business Media. This book was released on 2011-10-28 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: This publication reviews most of the available literature on the fatigue properties of β annealed Ti-6Al-4V and titanium alloys with similar microstructures. The focus is on β processed and β heat-treated alloys because β annealed Ti-6Al-4V has been selected for highly loaded and fatigue-critical structures, including the main wing-carry-through bulkheads and vertical tail stubs, of advanced high-performance military aircraft. An important aspect of the review is a concise survey of fatigue life assessment methods and the required types of fatigue data. This survey provides the background to recommendations for further research, especially on the fatigue behaviour of β annealed Ti-6Al-4V under realistic fatigue load histories, including the essential topic of short/small fatigue crack growth. Such research is required for independent fatigue life assessments that conform to the aircraft manufacturer’s design requirements, and also for life reassessments that most probably will have to be made during the service life of the aircraft.
Book Synopsis Influence of Metallurgical Factors on the Fatigue Crack Growth Rate in Alpha-Beta Titanium Alloys by : J. C. Chesnutt
Download or read book Influence of Metallurgical Factors on the Fatigue Crack Growth Rate in Alpha-Beta Titanium Alloys written by J. C. Chesnutt and published by . This book was released on 1978 with total page 423 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research was conducted on two alpha-beta titanium alloys, Ti-6Al-4V and Ti-6Al-2Sn 4Zr-6Mo, as a function of alloy composition microstructure and strength level, environment, and fatigue loading conditions. A wide range of microstructural conditions, seven for Ti-6Al-4V and three for Ti-6Al-2Sn-4Zr-6Mo, was chosen to provide a full range of constituent types and morphologies and a range of mechanical properties. All the material for the program was obtained in the form of pancake forgings which were uniformly and weakly textured. The initial portion of the program consisted of material characterization and base line fatigue crack propagation (FCP) testing. Characterization included a full description of microstructures, as well as mechanical property testing, fracture toughness tests, S-N curve determination and measurement of other properties such as modulus and texture. Base line FCP testing in dry air at two stress ratios (R) of 0.1 and 0.3; and in a 3.5% NaCl solution at 1 and 20 Hz was conducted in this portion of the program. Results of this study included the determination that transformed beta microstructures generally exhibit the greatest fatigue crack propagation resistance and that increasing the load ration, R, can lead to significant increases in crack growth rate; the behavior in both cases was rationalized in terms of crack tip interaction with microstructural constituents.
Book Synopsis A Study of Microstructure, Tensile Deformation, Cyclic Fatigue and Final Fracture Behavior of Commercially Pure Titanium and a Titanium Alloy by : Udaykar Bathini
Download or read book A Study of Microstructure, Tensile Deformation, Cyclic Fatigue and Final Fracture Behavior of Commercially Pure Titanium and a Titanium Alloy written by Udaykar Bathini and published by . This book was released on 2010 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rapid industrial growth and advances in the domains of engineering and related technologies during the last fifty years have led to the extensive use of traditional metals and their alloy counterparts. Titanium is one such metal which has gained wide popularity in the aerospace and defense related applications owing to a wide range of impressive mechanical properties like excellent specific strength ([sigma]UTS/[rho]), stiffness, corrosion and erosion resistance, fracture toughness and capability to withstand significant temperature variations. Two materials, namely commercial purity titanium (Grade 2), referred to henceforth as Ti-CP (Grade 2) and the "work-horse" alloy Ti-6Al-4V have been chosen for this research study. The intrinsic influence of material composition and test specimen orientation on the tensile and fatigue behavior for both Ti-CP (Grade 2) and Ti-6Al-4V have been discussed. Samples of both Ti-CP (Grade 2) and Ti-6Al-4V were prepared from the as-provided plate stock along both the longitudinal and transverse orientations. The specimens were then deformed to failure in uniaxial tension for the tensile tests and cyclically deformed at different values of maximum stress at constant load ratio of 0.1 for the high cycle fatigue tests. The microstructure, tensile properties, resultant fracture behavior of the two materials is presented in the light of results obtained from the uniaxial tensile tests. The conjoint influence of intrinsic microstructural features, nature of loading and specimen properties on the tensile properties is discussed. Also, the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of applied stress-microstructural feature interactions in governing failure for the cyclic fatigue properties for both the materials under study Ti-CP (Grade 2) and the "work-horse" alloy Ti-6Al-4V have been discussed in detail. Careful study of the microstructure for Ti-CP (Grade 2) material at a low magnification revealed the primary alpha grains to be intermingled with small pockets of beta grains. Observation at the higher allowable magnifications of the optical microscope revealed very fine alpha phase lamellae located within the beta grain. The microhardness and macrohardness measurements were consistent through the sheet specimen for Ti-CP (Grade 2) and slightly lower compared to Ti-6Al-4V. However, the macrohardness was marginally higher than the microhardness resulting from the presence of a large volume fraction of the soft alpha phase. The hardness values when plotted reveal marginal spatial variability. Tensile fracture of Ti-CP (Grade 2) was at an inclination to the far field tensile stress axis for both longitudinal and transverse orientations. The overload region revealed a combination of fine microscopic cracks, microscopic voids of varying size and randomly distributed through the surface, and a large population of shallow dimples, features reminiscent of locally brittle and ductile failure mechanisms. The maximum stress ([sigma]maximum) versus fatigue life (Nf) characteristics shown by this material is quite different from those non-ferrous metals that exhibit a well-defined endurance limit. When compared at equal values of maximum stress at a load ratio of 0.1, the fatigue life of the transverse specimen is noticeably greater than the longitudinal counterpart. At equivalent values of maximum elastic strain, the transverse specimens revealed noticeably improved fatigue life as compared one-on-one to the longitudinal counterparts. Careful observations of the Ti-6Al-4V alloy microstructure over a range of magnifications spanning very low to high magnification revealed a duplex microstructure consisting of the near equiaxed alpha and transformed beta phases. The primary near equiaxed shaped alpha grains (light in color) was well distributed in a lamellar matrix with transformed beta (dark in color). The microhardness and macrohardness values recorded for the Ti-6Al-4V alloy reveal it to be harder than the commercially pure (Grade 2) material. However, for the Ti-6Al-4V alloy the microhardness is noticeably higher than the corresponding macrohardness value that can be ascribed to the presence of a population of processing-related artifacts and the hard beta-phase. Tensile fracture of the Ti-6Al-4V alloy was macroscopically rough and essentially normal to the far field stress axis for the longitudinal orientation and cup-and-cone morphology for the transverse orientation. However, microscopically, the surface was rough and covered with a population of macroscopic and fine microscopic cracks, voids of varying size, a population of shallow dimples of varying size and shape, features reminiscent of locally brittle and ductile failure mechanisms. When compared at equal values of maximum stress at a load ratio of 0.1, there is a marginal to no influence of microstructure on high cycle fatigue life of both orientations of the alloy.
Book Synopsis Effects of Microstructure on Fatigue Behavior of Ü/Ý Titanium Alloys by : Vikas Sinha
Download or read book Effects of Microstructure on Fatigue Behavior of Ü/Ý Titanium Alloys written by Vikas Sinha and published by . This book was released on 2000 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Development of Textures and Microstructures in Alpha/beta Titanium Alloys by : Dhriti Bhattacharyya
Download or read book The Development of Textures and Microstructures in Alpha/beta Titanium Alloys written by Dhriti Bhattacharyya and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The relationship between the texture and the microstructure of both beta processed and alpha/beta processed Ti alloys has been examined in this study. In the beta-processed microstructures, it has been shown that two sets of alpha colonies sharing a common 0001 plane and rotated by 10.5° from each other may have growth directions which have very large angles of about 80.7° between them. Moreover, it was observed that alpha laths growing from certain prior beta grain boundaries sometimes shared common basal planes. In some special cases, the alpha laths growing into two different prior beta grains from the grain boundary between them had almost exactly the same orientation, although they had vastly different growth directions. Additionally, there were some cases in which alpha laths growing into different prior beta grains not only had the same crystallographic orientation, but also had the same growth direction. Scanning Electron Microscopy (SEM), Orientation Imaging Microscopy (OIM) and Transmission Electron Microscopy (TEM) have been used to investigate these phenomena and the existing theories of growth directions have been used in conjunction with the results obtained to explain them. In alpha/beta-processed alloys, the phenomenon of globularization of alpha laths breaks down the beta-processed microstructure and modifies the texture of these alloys. Samples of Ti-6Al-4V having colony and basketweave microstructures were hot deformed in the high alpha/beta temperature range and their microstructure and microtexture were examined by the use of SEM and OIM. It is shown that the samples which had a colony microstructure had greater "clustering" of grains with similar orientations than those having a basketweave microstructure. The mode of transformation on heating from the alpha to the beta phase was investigated by measuring the texture of both phases at different temperatures, in situ, using the HIPPO instrument at the Los Alamos Neutron Science Center. A comparison of the pole figures for both phases has allowed an insight into the mode of transformation of the alpha to the beta phase, and it appears that the beta phase forms by the growth of the preexisting beta, and not by fresh nucleation of beta in the alpha phase.
Book Synopsis Alloy, Texture, and Microstructural Effects on the Yield Stress and Mixed Mode Fracture Toughness of Titanium by : WM. Parris
Download or read book Alloy, Texture, and Microstructural Effects on the Yield Stress and Mixed Mode Fracture Toughness of Titanium written by WM. Parris and published by . This book was released on 1974 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mixed mode fracture toughness, KQ, behavior of alpha-beta titanium alloys was examined in terms of: (1) alloy effects of aluminum, oxygen, and beta stabilizer, (2) processing effects of hot-roll and anneal temperatures, and (3) test direction. In the Ti-4V alloy system, alloying and processing effects interact in their influence on KQ in a complex manner. In the Ti-2Mo alloy system, oxygen depresses KQ after alpha-beta rolling, whereas aluminum has a similar effect after beta rolling; in each case the alloy effect dominates that of yield strength. In the overall analysis, texture as implied by a test direction effect, significantly influences KQ. The oxygen, texture, and microstructural effects on KO were shown by statistical methods to qualitatively parallel findings in the literature on titanium alloys regarding the effects of these variables on KIc.
Book Synopsis Effect of Microstructure on the Fatigue Properties of Ti-6Al-4V Bar by : LJ. Bartlo
Download or read book Effect of Microstructure on the Fatigue Properties of Ti-6Al-4V Bar written by LJ. Bartlo and published by . This book was released on 1969 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microstructure can have a significant effect on the mechanical properties of titanium alloys. The extent of this effect on the fatigue properties of the Ti-6Al-4V alloy in small diameter bar (0.625 in., 15.875 mm) was studied. Microstructural variations were produced by heat treating from 1550 to 1950 F at 100 F intervals. Three different cooling rates (furnace cooling, air cooling, and water quenching) were employed for each temperature. The room-temperature tensile, smooth, and notch-fatigue properties were evaluated for each thermal condition.
Book Synopsis Microstructure and Temperature Effects on the Fatigue Variability Behavior of AN Alpha+beta Titanium Alloy and Implications for Life Prediction (Postprint). by :
Download or read book Microstructure and Temperature Effects on the Fatigue Variability Behavior of AN Alpha+beta Titanium Alloy and Implications for Life Prediction (Postprint). written by and published by . This book was released on 2006 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have studied the effects of microstructure and temperature on the fatigue variability behavior of the alpha+beta titanium alloy, Ti-6Al2Zr-4Sn-6Mo (Ti-6-2-4-6). These variables had separate influence on the minimum, and the mean behavior. This was related to perhaps a fundamental aspect of fatigue variability which dictates that at any stress level, the mean is dominated by a mechanism different from the one controlling the lower-tail behavior. As a result in this material, while the mean response was increasingly dominated by the crack initiation regime with decreasing stress level (which is the conventionally expected behavior), at the same time the life-limiting behavior was controlled by the crack growth regime. This produced a very systematic effect of microstructure and temperature on total uncertainty in lifetime depending on the sensitivity of crack initiation and growth regimes to these variables. We suggest a new paradigm to treat the fatigue variability behavior and show that, this can have significant implications for life management especially, with respect to reducing the uncertainty with life prediction and improving the reliability of design life.
Book Synopsis The Relationship of Microstructure and Mechanical Properties of Extruded Titanium Alloy Bars to the Prior Deformation Processing History by : Fred J. Gurney
Download or read book The Relationship of Microstructure and Mechanical Properties of Extruded Titanium Alloy Bars to the Prior Deformation Processing History written by Fred J. Gurney and published by . This book was released on 1971 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: The inter-relation of extrusion process variables with mechanical properties and microstructure is analyzed for three titanium alloys (Ti-5Al-2.5Sn, Ti-6Al-4V and Ti-13V-11Cr-3Al). Information is obtained from duplicate billets which were extruded at same conditions with one extruded bar allowed to air cool and the other bar water quenched immediately after extrusion. Results indicate that significant reduction in deformation loads can be achieved in alpha and alpha-beta titanium alloys by processing them in the beta temperature range. Resultant metallurgical structures and mechanical properties (room temperature tensile and Charpy V notch impact) are found to not be significantly affected by process variables other than preheat temperature and product cooling rate. In alpha and alpha-beta alloys, the room temperature strength properties of beta processed and water quenched product is significantly improved over those of beta processed and air cooled product and somewhat improved over those for alpha-beta processed followed by either air cooling or water quenching. Mechanical properties from the beta alloy are not significantly affected by process temperature or by product cooling rate except for some anomalous behavior in the 2050F processing temperature range. (Author).
Book Synopsis Elucidating the Role of Microstructure, Texture, and Microtexture on the Dwell Fatigue Response of Ti-6Al-4V by : Alec Mitchell Blankenship
Download or read book Elucidating the Role of Microstructure, Texture, and Microtexture on the Dwell Fatigue Response of Ti-6Al-4V written by Alec Mitchell Blankenship and published by . This book was released on 2016 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ambient temperature dwell sensitivity is known to be deleterious to the fatigue response of near-alpha titanium alloys. Dwell fatigue refers to the presence of a sustained hold at peak stress as opposed to the continuous variation of normal cyclic fatigue loading. This reduction in failure life-times from dwell loading is attributed to early crack nucleation and faster crack propagation. The degradation is the result of plastic anisotropy on the microstructural scale along with tendency of titanium alloys to creep at low temperatures at stresses well below the 0.2% offset yield strength. Despite being the most widely used titanium alloy, Ti-6Al-4V has not been the subject of most dwell fatigue research. Generally, dwell sensitivity is microstructurally dependent and believed to only affect Ti-6Al-4V when severe crystallographic texture is present and under high peak stress loading. Recent studies, however, have suggested that small clusters of preferred crystal orientations, known as micro-textured regions (MTR), can have a significant effect on the dwell sensitivities in Ti-6Al-4V even without severe overall texture in the material.In this study, smooth-bar fatigue specimens were subjected to uniaxial fatigue at 20 Hz cyclic and 2-min dwell loading conditions under load-control at stresses representative of service conditions, until failure occurred. A reduction in specimen life-times by approximately a factor of three was observed under dwell conditions, which was less than for the highly susceptible near-a titanium alloys such as Ti-6Al-2Sn-4Zr-2Mo, where the dwell debit is often in excess of a factor of ten. Measurement of fatigue and dwell fatigue crack growth rates revealed a significant acceleration of the dwell crack growth rates in certain cases. Backscattered electron imaging and electron backscattered diffraction were utilized to quantify the interaction between the cracks and local microstructure. Though no correlation was found between crack growth rate and the local microstructure and crack trajectory, strong correlation was found between crack growth and the presence of grains with [0001] axes at small angles (
Book Synopsis Effect of Microstructure on Fatigue Properties of Ti-6Al-4V by : Mohammed Ashraf Imam
Download or read book Effect of Microstructure on Fatigue Properties of Ti-6Al-4V written by Mohammed Ashraf Imam and published by . This book was released on 1978 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Statistically Based Investigation of Microstructural Effects on the Fatigue Properties of Titanium and Titanium Alloys by : Dale Alan Wilson
Download or read book A Statistically Based Investigation of Microstructural Effects on the Fatigue Properties of Titanium and Titanium Alloys written by Dale Alan Wilson and published by . This book was released on 1978 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Microstructure Evolution and Microstructure/mechanical Properties Relationships in [alpha]+[beta] Titanium Alloys by : Eunha Lee
Download or read book Microstructure Evolution and Microstructure/mechanical Properties Relationships in [alpha]+[beta] Titanium Alloys written by Eunha Lee and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: In this study, the microstructural evolution of Timetal 550 was investigated. Timetal 550 showed two types of phase transformations (martensitic and nucleation and growth) depending on the cooling rate from the [beta] region. The [alpha] phase initially precipitated at the prior [beta] grain boundaries, and it had a Burgers OR with one of the adjacent grains. It was found that colonies could grow, even in the fast-cooled Timetal 550 sample, from the grain boundary [alpha] into the prior [beta] grain with which it exhibited the Burgers OR. Three orientation relationships were also found between [alpha] laths in the basketweave microstructure. Microhardness testing demonstrated that fast-cooled Timetal 550 samples with basketweave microstructure were harder than slowly-cooled samples with colony microstructure. Orientation-dependent deformation was found in the colony microstructure. Specically, when the surface normal is perpendicular to the [0001] of [alpha], the material deforms easily in the direction perpendicular to the [0001] of [alpha]. Fuzzy logic and Bayesian neural network models were developed to predict the room temperature tensile properties of Timetal 550. This involved the development of a database relating microstructural features to mechanical properties. A Gleeble 3800 thermal-mechanical simulator was used to develop various microstructures. Microstructural features of tensile-tested samples were quantified using stereological procedures. The quantified microstructural features and the tensile properties were used as inputs and outputs, respectively, for modeling the relationships between them. The individual influence of five microstructural features on tensile properties was determined using the established models. The microstructural features having the greatest impact on UTS and YS were the thickness of [alpha] laths and the width of grain boundary [alpha] layer, and the microstructural features having the greatest impact on elongation were the thickness of [alpha] laths and the prior [beta] grain size. Nanoindentation testing found that the hardness of the individual grains was related to their orientations. The hardness values were highest near the [0001] stress axis, and they decreased as the stress axis deviated from [0001] orientation. Dislocation analyses indicated that the deformation in individual grains conformed to the Schmid factor analysis where slip primarily occurs on those slip systems where RSS (SF) values are highest.
Book Synopsis Deformation of Dual Phase Titanium Alloys by : Jikang Zhong
Download or read book Deformation of Dual Phase Titanium Alloys written by Jikang Zhong and published by . This book was released on 2012 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: The deformation behaviour of dual phase titanium alloys has been investigated using experimental and modelling methods. The motivation for conducting this investigation was to improve understanding of the deformation behaviour of dual phase titanium alloys in order to contribute to the long term goal of reducing manufacturing cost and improving production efficiency. Dual phase titanium alloys have been studied under two deformation conditions: high speed machining and uniaxial compression, which represent respectively high rate and low rate deformation. The microstructure and texture of the serrated chips obtained during high speed cutting of the dual phase Ti-6Al-4V alloy have been studied. The cutting speed, depth of cut and the orientation of the sample were found to have a significant influence on the deformation of serrated chips. Adiabatic shear bands were found in the serrated chips due to non-uniform deformation of Ti-6Al-4V alloy and deformation heating. In addition, there is reasonable agreement between the predicted texture using the visco-plastic self-consistent (VPSC) model and the measured texture using the electron backscatter diffraction (EBSD) technique indicating that the deformation in an adiabatic shear band is due to shear.The deformation behaviour of dual phase Ti-Mn alloys has been characterised with uniaxial compression at different temperatures and strain rates. The flow stress plateau phenomenon was observed in all the Ti-Mn alloys in the low to medium temperature range (27~500°C), which is attributed to the occurrence of dynamic strain aging (DSA). The flow softening behaviour was observed in dual phase Ti-Mn alloys in the high to sub-transus temperature range (600~800°C), which is attributed to the change in volume fraction of [beta] phase during deformation due to the rise in temperature caused by deformation heating. The yield point phenomenon was observed when the Ti-Mn alloys are above their [beta] transus temperatures. This phenomenon has been attributed to the multiplication of dislocations at the beginning of plastic deformation and dynamic recovery in the following plastic deformation. The strain rate sensitivity of Ti-Mn alloys was low in the low to medium temperature range and thus the effect of strain rate on deformation is not obvious. However, it was high in the high to sub-transus temperature range and thus the effect of strain rate on the deformation is significant. The 0.2% proof stress was found to increase with the volume fraction of [beta] phase. The strain rate sensitivity was found to decrease with the volume fraction of [beta] phase in the low to medium temperature range because the strain rate sensitivity of the [alpha] phase is higher than the [beta] phase. However, the strain rate sensitivity was found to increase with the volume fraction of [beta] phase at high temperatures because the strain rate sensitivity of the [beta] phase becomes larger than the [alpha] phase. A considerable temperature rise was observed during compression of the Ti-Mn alloys and this indicates that the effect of deformation heating on deformation is not negligible. A composite model has been constructed to predict the plastic stress-strain curves of the dual phase Ti-Mn alloys using the in-situ behaviour of the component phases. The partition of stress and strain between the component phases has been accounted for by using three partitioning assumptions: iso-strain, iso-stress and iso-work. There was good agreement between the predicted curves and the experimental curves. It was found that the in-situ behaviour of the [alpha] phase is different in different dual phase Ti-Mn alloys and it exhibits a linear relationship with the volume fraction of [beta] phase when the dominant matrix is the same. The modelling results in the low to medium temperature range indicate that most of the plastic deformation occurs in the localised shear band, which is consistent with the experimental observation that the dual phase Ti-Mn alloys were more susceptible to the formation of localised shear bands. In addition, it was found that a change in the dominant matrix in dual phase Ti-Mn alloys significantly influences the in-situ behaviour of the [alpha] phase. The modelling results in the high to sub-transus temperature range indicate that the flow softening behaviour observed in dual phase Ti-Mn alloys is related to the change in volume fraction of the [beta] phase and the diffusion of Mn during the deformation.
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