34 results on '"Hodgson, Peter D."'
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2. Yield point phenomenon in low-alloyed TRIP-aided steel: role of retained austenite
- Author
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Ranjan, Ravi, Beladi, Hossein, Hodgson, Peter D., and Singh, Shiv Brat
- Abstract
Multiphase TRIP-aided steels are generally characterised by a continuous yielding behaviour. The processing route involving a deformation step in the intercritical (ferrite + austenite) region showed an undesirable discontinuous yielding. This is attributed to the formation of fresh dislocations in the soft ferrite matrix that trap the diffusing carbon and form Cottrell atmospheres. The discontinuous yielding disappears when fresh mobile dislocations are introduced through transformation of the retained austenite to martensite.
- Published
- 2023
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3. Effect of Surface Roughness on Hydrodynamic Characteristics of an Impinging Droplet
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Singh, Rajeev Kumar, Hodgson, Peter D., Sen, Niladri, and Das, Subrat
- Abstract
The influence of surface roughness and impact energy on the hydrodynamic behavior of water droplets impinging upon dry and rigid surfaces of known roughness has been investigated experimentally. The influence of these two parameters on the droplet maximum spreading diameter, slip length during droplet recoil, dynamic contact angle, contact angle hysteresis, and apparent contact angle of droplets at rest has been determined. Based on the quantitative assessment, a correlation for the maximum spreading diameter in terms of the nondimensional parameter (We/Oh) and surface roughness ratio (Ra/do) was derived. We propose to use surface roughness “Ra” rather than using the contact angle for correlation as contact angles cannot be known a priori, whereas surface roughness can be determined beforehand. The wetting state of a droplet depends on the combined influence of droplet impact energy and surface roughness. While increasing impact energy increases the spreading, higher surface roughness resists the droplet from spreading. Low impact energy and a smoother surface tend toward the Cassie–Baxter wetting state, whereas high impact energy and rough surfaces propel the droplet toward the Wenzel state of wetting.
- Published
- 2021
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4. Heteroepitaxial integration of InAs/InAsSb type-II superlattice barrier photodetectors onto silicon
- Author
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Sood, Ashok K., Wijewarnasuriya, Priyalal, D'Souza, Arvind I., Carrington, Peter J., Delli, Evangelia, Letka, Veronica, Bentley, Matt, Hodgson, Peter D., Repiso, Eva, Hayton, Jonathan P., Craig, Adam P., Lu, Qi, Beanland, Richard, Krier, Anthony, and Marshall, Andrew R. J.
- Published
- 2020
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5. Mid-Infrared InAs/InAsSb Superlattice nBn Photodetector Monolithically Integrated onto Silicon.
- Author
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Delli, Evangelia, Letka, Veronica, Hodgson, Peter D., Repiso, Eva, Hayton, Jonathan P., Craig, Adam P., Qi Lu, Beanland, Richard, Krier, Anthony, Marshall, Andrew R. J., and Carrington, Peter J.
- Published
- 2019
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6. Enhanced tensile properties of a reversion annealed 6.5Mn-TRIP alloy via tailoring initial microstructure and cold rolling reduction.
- Author
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Cai, Minghui, Huang, Hongshou, Su, Junhua, Ding, Hua, and Hodgson, Peter D.
- Subjects
TENSILE strength ,ANNEALING of metals ,MICROSTRUCTURE ,COLD rolling ,RECRYSTALLIZATION (Metallurgy) - Abstract
The feasibility of improving the overall performance of medium Mn steels was demonstrated via tailoring the initial microstructure and cold rolling reduction. The combined effects of cooling patterns after hot rolling (HR) and cold rolling (CR) reductions show: (1) as the cooling pattern varied from furnace cooling (FC) to oil quenching (OQ), the intercritically annealed microstructure was dramatically refined and the fraction of recrystallized ferrite dropped, regardless of CR reductions. This resulted in both high yield/ultimate tensile strengths (YS/UTS) but low total elongation to fracture (El); (2) as the CR reduction increased from 50% to 75%, the OQ-samples after annealing exhibited a more refined microstructure with relatively higher fractions of retained austenite and sub-structure, leading to higher YS and UTS but lower El; whereas the FC samples appeared to exhibit little difference in overall tensile properties in both cases. The differences in microstructural evolution with cooling patterns and CR reductions were explained by the calculated accumulated effective strain ( ε AES ), which was considered to be related to degrees of recovery and recrystallization of the deformed martensite (α’). The optimal tensile properties of ∼1 GPa YS and ∼40 GPa·% UTS×El were achieved in the OQ-50%CR annealed samples at 650 °C for 1 h. This was quite beneficial to large-scale production of ultra-high strength steels, owing to its serious springback during heavy cold working. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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7. Insights into Free Volume Variations across Ion-Exchange Membranes upon Mixed Solvents Uptake by Small and Ultrasmall Angle Neutron Scattering
- Author
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Allioux, Francois-Marie, Garvey, Christopher J., Rehm, Christine, Tardy, Blaise L., Dagastine, Raymond Riley, Hodgson, Peter D., Kong, Lingxue, and Dumée, Ludovic Francis
- Abstract
Ion-exchange membranes are composite separation materials increasingly used in a variety of electro-membranes and electrochemical processes. Although promising for solvent reclamation, to date, their main applications are limited to aqueous environments due to physicochemical and microstructural changes of the materials upon exposure to nonaqueous and mixed solvents solutions, affecting long-term stability and separation performance. In the present work, the structural changes of commercial and novel hybrid ion-exchange membranes in mixed methanol/water and ethanol/water solutions are assessed for the first time using ultra- and small-angle neutron scattering techniques. The interface between the ion-exchange functional layer and the mechanical support of the membranes is evaluated in the ultralow-qregion, while a broad solvent-dependent peak at the mid-qregion was correlated to the microstructural properties which are related to the free volume across the ion-exchange domains and to the materials electrical and nanoscale mechanical properties. The results of this study may offer new opportunities toward the development of an efficient separation process using ion-exchange membranes for the purification of fermentation broths toward biofuel generation.
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- 2017
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8. The influence of fine ferrite formation on the γ/α interface, fine bainite and retained austenite in a thermomechanically-processed transformation induced plasticity steel
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Timokhina, Ilana B., Miller, Michael K., Beladi, Hossein, and Hodgson, Peter D.
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Abstract
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- 2016
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9. Softening Behavior of Ti6Al4V Alloy during Hot Deformation
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Souza, Paul Micheal, Beladi, Hossein, Rolfe, Bernard, Singh, Rajkumar, and Hodgson, Peter D.
- Abstract
The effect of strain rate and strain on the hot compression behaviour of Ti6Al4V has been analysed to understand the microstructural evolution and restoration behaviour. Cylindrical samples with partially equiaxed grains were deformed in the α+β region at different thermo-mechanical conditions. EBSD has been used to study the microstructural behaviour and the restoration mechanisms. The microstructural evolution showed a complex restoration behaviour, where both fragmentation and nucleation of new grains have been observed. The volume fraction of the equiaxed grains increased with an increase in the strain, but oppositely decreased with the strain rate. At the same time the average grain size of the equiaxed grains decreased with an increase in both the strain and strain rate. The measured activation energy for deformation revealed a good agreement with reported values in the literature.
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- 2015
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10. Long-Wavelength Photoluminescencefrom Stacked Layersof High-Quality Type-II GaSb/GaAs Quantum Rings.
- Author
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Carrington, Peter J., Young, Robert J., Hodgson, Peter D., Sanchez, Ana M., Hayne, Manus, and Krier, Anthony
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- 2013
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11. Nanohydroxyapatite coating on a titanium–niobium alloy by a hydrothermal process.
- Author
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Xiong, Jianyu, Li, Yuncang, Hodgson, Peter D., and Wen, Cui’e
- Subjects
NANOSTRUCTURED materials ,HYDROXYAPATITE coating ,SOLUTION (Chemistry) ,TITANIUM alloys ,CHEMICAL processes ,TEMPERATURE effect ,CALCIUM phosphate - Abstract
Abstract: A novel one-step hydrothermal coating process was used to produce nanohydroxyapatite (nano-HA) coating on a titanium–niobium (TiNb) alloy substrate in a newly designed solution containing calcium and phosphate ions. The morphology of the coating was studied using scanning electron microscopy. The phase identification of the coating was carried out using X-ray diffraction, attenuated total reflectance Fourier transform infrared spectroscopy and transmission electron microscopy. The reaction between the surface of TiNb alloy and the solution during the hydrothermal process was studied by X-ray photoelectron spectroscopy. Results show that the coating formed on the surface of TiNb alloy was composed of nano-HA particles. During the hydrothermal process, TiO
2 and Nb2 O5 formed on the TiNb alloy surface and hydrated to Ti(OH)4 and Nb(OH)5 , respectively. Calcium phosphate nucleated and grew into a layer of nano-HA particles on the surface of TiNb alloy under the hydrothermal conditions. The crystallinity of the nano-HA coating was improved with the increase in hydrothermal treatment temperature and time duration. Nano-HA coating with good crystallinity was produced on the TiNb alloy via the hydrothermal process at a temperature of 200°C for 12h. [Copyright &y& Elsevier]- Published
- 2010
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12. Porous TiNbZr alloy scaffolds for biomedical applications.
- Author
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Wang, Xiaojian, Li, Yuncang, Xiong, Jianyu, Hodgson, Peter D., and Wen, Cui’e
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POROUS materials ,TITANIUM alloys ,STRUCTURAL frames ,BIOMEDICAL materials ,SINTERING ,ADDITION reactions ,CELL culture ,DETERIORATION of materials - Abstract
Abstract: In the present study, porous Ti–10Nb–10Zr alloy scaffolds with different porosities were successfully fabricated by a “space-holder” sintering method. By the addition of biocompatible alloying elements the porous TiNbZr scaffolds achieved significantly higher strength than unalloyed Ti scaffolds of the same porosity. In particular, the porous TiNbZr alloy with 59% porosity exhibited an elastic modulus and plateau stress of 5.6GPa and 137MPa, respectively. The porous alloys exhibited excellent ductility during compression tests and the deformation mechanism is mainly governed by bending and buckling of the struts. Cell cultures revealed that SaOS2 osteoblast-like cells grew on the surface and inside the pores and showed good spreading. Cell viability for the porous scaffold was three times higher than the solid counterpart. The present study has demonstrated that the porous TiNbZr alloy scaffolds are promising scaffold biomaterials for bone tissue engineering by virtue of their appropriate mechanical properties, highly porous structure and excellent biocompatibility. [Copyright &y& Elsevier]
- Published
- 2009
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13. The importance of particle size in porous titanium and nonporous counterparts for surface energy and its impact on apatite formation.
- Author
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Chen, Xiao-Bo, Li, Yun-Cang, Hodgson, Peter D., and Wen, Cuie
- Subjects
TITANIUM ,SURFACE energy ,BODY fluids ,PARTICLE size determination - Abstract
Abstract: The importance of particle size in titanium (Ti) fabricated by powder metallurgy for the surface energy and its impact on the apatite formation was investigated. Four sorts of Ti powders of different mean particle size were realized through 20min, 2h, 5h and 8h of ball milling, respectively. Each sort of Ti powder was used to fabricate porous Ti and its nonporous counterparts sharing similar surface morphology, grain size and chemical composition, and then alkali-heat treatment was conducted on them. Surface energy was measured on the surfaces of the nonporous Ti counterparts due to the difficulty in measuring the porous surfaces directly. The surface energy increase on the alkali-heat-treated porous and nonporous Ti was observed due to the decrease in the particle size of the Ti powders and the presence of Ti–OH groups brought by the alkali-heat treatment. The apatite-inducing ability of the alkali-heat-treated porous and nonporous Ti with different surface energy values was evaluated in modified simulated body fluid and results indicated that there was a strong correlation between the apatite-inducing ability and the surface energy. The alkali-heat-treated porous and nonporous Ti discs prepared from the powders with an average particle size of 5.89±0.76μm possessed the highest surface energy and the best apatite-inducing ability when compared to the samples produced from the powders with the average particle size varying from 19.79±0.31 to 10.25±0.39μm. [Copyright &y& Elsevier]
- Published
- 2009
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14. Influence of calcium ion deposition on apatite-inducing ability of porous titanium for biomedical applications.
- Author
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Chen, Xiao-Bo, Li, Yun-Cang, Plessis, Johan Du, Hodgson, Peter D., and Wen, Cui’e
- Subjects
CALCIUM ions ,APATITE ,TITANIUM ,POROSITY - Abstract
Abstract: In the present study, the influence of calcium ion deposition on the apatite-inducing ability of porous titanium(Ti) was investigated in a modified simulated body fluid (m-SBF). Calcium hydroxide (Ca(OH)
2 ) solutions with five degrees of saturation were used to hydrothermally deposit Ca ions on porous Ti with a porosity of 80%. Apatite-inducing ability of the Ca-ion-deposited porous Ti was evaluated by soaking them in m-SBF for up to 14days. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) confirmed that a thin layer of calcium titanate (CaTiO3 )/calcium oxide (CaO) mixture with a nanostructured porous network was produced on porous Ti substrates after hydrothermal treatment at 200°C for 8h. X-ray photoelectron spectroscopy results demonstrated that the content of the Ca ions deposited on Ti and the thickness of the CaTiO3 /CaO layer increased with increasing saturation degree of the Ca(OH)2 solution. The thickest (over 10nm) CaTiO3 /CaO layer with the highest Ca content was achieved on the Ti treated in an oversaturated Ca(OH)2 solution (0.2M). SEM, XRD, transmission electron microscopy and Fourier transformed infrared spectroscopy analysis indicated that the porous Ti samples deposited with the highest content of Ca ions exhibited the best apatite-inducing ability, producing a dense and complete carbonated apatite coating after a 14 day soaking in m-SBF. The present study illustrated the validity of using Ca ion deposition as a pre-treatment to endow desirable apatite-inducing ability of porous Ti for bone tissue engineering applications. [Copyright &y& Elsevier]- Published
- 2009
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15. Deformation Behaviour of a Commercial Pure Titanium Alloy during Hot Compression Testing
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Chao, Qi, Beladi, Hossein, Sabirov, Ilchat, and Hodgson, Peter D.
- Abstract
The flow curve behavior and microstructure evolution of commercially pure titanium (CP-Ti) through uniaxial hot compression was investigated at 850 °C and a strain rate of 0.1/s. Electron back scattered diffraction (EBSD) was employed to characterize the microstructure and crystallographic texture development for different thermomechanical conditions. The stress-strain curves of CP-Ti alloy under hot compression displayed a typical flow behavior of metals undergoing dynamic recrystallization (DRX), which resulted in grain refinement. The critical strain for the onset of DRX was 0.13 using the double differentiation analysis technique. It was also revealed that the texture was markably altered during hot deformation.
- Published
- 2013
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16. Effect of Temperature on Mechanical Behaviour of High Manganese TWIP Steel
- Author
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Shterner, Vadim, Timokhina, Ilana, Beladi, Hossein, and Hodgson, Peter D.
- Abstract
The aim of the present study was to investigate the role of deformation temperature on the active deformation mechanisms in a 0.6C-18Mn-1.5Al (wt%) TWIP steel. The tensile testing was performed at different temperatures, ranging from ambient to 400
o C at a constant strain rate of 10-3 s-1 . The microstructure characterization was carried out using a scanning electron microscopy. The deformation temperature revealed a significant effect on the active deformation mechanisms (i.e. slip versus twinning), resulting in different microstructure evolution and mechanical properties. At the room temperature, the mechanical twinning was the dominant deformation mechanism, enhancing both the strength and ductility. Dynamic strain aging (DSA) effect was observed at different deformation temperatures, though it was more pronounced at higher temperatures. The volume fraction of deformation twins significantly reduced with an increase in the deformation temperature, deteriorating the mechanical behavior. There was a transition temperature (~300o C), above which the mechanical twinning was hardly observed in the microstructure even at fracture, resulting in low ductility and strength. The current observation can be explained through the change in the stacking fault energy with the deformation temperature.- Published
- 2013
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17. An Experimental Investigation of Edge Strain and Bow in Roll Forming a V-Section
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Abeyrathna, Buddhika, Rolfe, Bernard, Hodgson, Peter D., and Weiss, Matthias
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V-sections were roll formed from two grades of steel, and the strain on the top and bottom of the strip near the edge was measured using electrical resistance strain gauges. The channels were bent to a radius of 2 and 15 mm along the centerline. The steel strips were of mild and dual phase steel of yield strength 367 MPa and 597 MPa respectively. The longitudinal bow was measured using a 3-dimensional scanning system. The strain measurements were analysed to determine bending and mid-surface strains at the edge during forming. The peak longitudinal edge strain increased with material yield strength for both profile radii. For the 15 mm radius, the bow was larger in the dual phase steel than in the mild steel. For the 2 mm profile radius, the bow was smaller compared with the 15 mm profile radius and it was similar for both steels. It was observed that the difference between the peak longitudinal edge strain and yield strength to Youngs modulus ratio of the material is an important factor in determining longitudinal bow.
- Published
- 2013
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18. Cryo-Rolling and Formability of 2024 Aluminium
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Taylor, Adam S., Weiss, Matthias, Hilditch, Tim, Hodgson, Peter D., and Stanford, Nicole
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Sheets of precipitate hardenable 2024 aluminium have been processed by rolling at liquid nitrogen temperature in order to refine the microstructure. A number of different aging/heat treating procedures have been utilised that have resulted in significantly different mechanical properties. The cryo-rolled material was heat treated at 150 °C for varying times and the resulting mechanical properties evaluated as a function of this holding time. The resulting properties were found to be strongly influenced by precipitates that formed either during the aging step, rolling process or the subsequent heat treatment. The formability of the cryo-rolled and heat treated material has been investigated using a limiting dome height test (Erichsen cupping test).
- Published
- 2013
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19. Atomic Scale Investigation of Solutes and Precipitates in High Strength Steels
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Hodgson, Peter D., Mukherjee, Subrata, Beladi, Hossein, Xiong, Xiang Yuan, and Timokhina, Ilana B.
- Abstract
Two steels, ferritic, high strength with interphase precipitation and nanobainitic, were used to show the advances in and application of atom probe. The coexistence of the nanoscale, interphase Nb-Mo-C clusters and stoichiometric MC nanoparticles was found in the high strength steel after thermomechanical processing. Moreover, the segregation of carbon at different heterogeneous sites such as grain boundary that reduces the solute element available for fine precipitation was observed. The APT study of the solutes redistribution between the retained austenite and bainitic ferrite in the nanobainitic steel revealed: (i) the presence of two types of the retained austenite with higher and lower carbon content and (ii) segregation of carbon at the local defects such as dislocations in the bainitic ferrite during the isothermal hold.
- Published
- 2013
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20. Development of an Inverse Routine to Predict Residual Stresses in the Material Based on a Bending Test
- Author
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Abvabi, Akbar, Rolfe, Bernard, Hodgson, Peter D., and Weiss, Matthias
- Abstract
Bending with unloading and reverse bending are the dominant material deformations in roll forming and hence property data derived from bend tests could be more relevant than tensile test data for numerical simulation of the roll forming process. Recent investigations have shown that residual stresses affect the material behaviour close to the yield in a bending test. So, Residual stress introduced during prior steel processing may affect the roll forming process and therefore needs to be included in roll forming simulations to achieve improved model accuracy. Measuring the residual stress profile experimentally is expensive, difficult, time consuming and has limited accuracy. Analytical models are available that allow the determination of residual stress. However, for this detailed information about the pre-processing conditions is required; this information is generally not available for roll forming materials. The main goal of this study is to develop an inverse routine that generates a residual stress profile through the thickness of the material based on pure bend test data.
- Published
- 2013
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21. Microstructure and Texture Development in Ti-5Al-5Mo-5V-3Cr Alloy during Cold Rolling and Annealing
- Author
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Ghaderi, Alireza, Hodgson, Peter D., and Barnett, Matthew R.
- Abstract
This study focuses on the microstructure and texture evolution of a Ti-5Al-5Mo-5V-3Cr alloy during cold rolling and annealing treatments. Three samples with different initial microstructures were cold rolled to a 40% reduction in thickness. The starting microstructure of one sample was single β phase while two other specimens were α+β phases with different α particle sizes, distributed in β grains. For all three samples, the average size of primary β grains was 150 µm. The cold rolled specimens were then annealed at 860 °C (10 °C above the β transus temperature) for 5 minutes followed by water quenching. Microstructure development during cold rolling and recrystallization was studied by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) technique. Microstructure investigations showed that massive amount of shear bands occurred during the cold rolling of the single β phase sample while only a few shear bands were observed in the α+β cold rolled microstructures. The cold rolled texture of the sample comprised of a single β phase contains a gamma fibre (//ND) and a partial alpha fibre (//RD). Annealing treatment decreased the intensity of the cold rolled texture in the single β phase sample. Also, it was found that the presence of α precipitates changes the common annealing texture observed in the single β phase specimen.
- Published
- 2013
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22. Recrystallization of 304SS during and after High Strain Rate Deformation
- Author
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Taylor, Adam S. and Hodgson, Peter D.
- Abstract
During the hot working of austenitic stainless steels the shape of the flow curve is strongly influenced by the strain rate. Low strain rate deformation results in flow curves typical of dynamic recrystallization (DRX) but as the strain rate increases the shape changes to a ‘flat-top’ curve. This has traditionally been thought to indicate no DRX is taking place and that dynamic recovery (DRV) is the only operating softening mechanism. Examining the work-hardening behaviour and corresponding deformation microstructures showed this is not the case for austenitic stainless steel, as clear evidence of dynamic recrystallization process can be seen. The post-deformation recrystallization kinetics can be modelled using a standard Avrami equation with an Avrami exponent, n, of 1.15. With an increasing value of the Zener-Hollomon parameter it was found that the kinetics of recrystallization become less strain rate sensitive until at the highest values (highest strain rates/lowest temperatures) the recrystallization kinetics become strain rate insensitive.
- Published
- 2013
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23. Effect of Substructure Characteristics on the Dislocation Annihilation Process during Post-Deformation Annealing
- Author
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Beladi, Hossein, Cizek, Pavel, Taylor, Adam S., and Hodgson, Peter D.
- Abstract
Two distinct substructures were produced in a Ni-30Fe austenitic model alloy by different thermomechanical processing routes. The first substructure largely displayed organized, banded subgrain arrangements with alternating misorientations, resulting from the deformation at a strain just before the initiation of dynamic recrystallization (DRX). By contrast, the second substructure was more random in character and exhibited complex subgrain/cell arrangements characterized by local accumulation of misorientations, formed through DRX. During the post-deformation annealing, the latter substructure revealed a rapid disintegration of dislocation boundaries leading to the formation of dislocation-free grains within a short holding time, though the former largely preserved its characteristics till becoming replaced by growing statically recrystallized grains.
- Published
- 2013
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24. Orientation Dependence of the Substructure Characteristics in a Ni-30%Fe Austenitic Alloy Deformed in Hot Torsion
- Author
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Cizek, Pavel, Beladi, Hossein, Taylor, Adam S., and Hodgson, Peter D.
- Abstract
The present work examines the microstructure and texture evolution in a Ni-30wt.%Fe austenitic model alloy deformed in torsion at 1000 °C, with a particular emphasis on the orientation dependence of the substructure characteristics within the deformed original grains. Texture of these grains was principally consistent with that expected for simple shear and comprised the main A, B and C components. The deformation substructure within the main texture component grains was characterised by “organised” arrays of parallel microbands with systematically alternating misorientations, locally accompanied by micro-shear bands within the C grains. With increasing strain, the mean subgrain size gradually decreased and the mean misorientation angle concurrently increased towards the saturation. The stored deformation energy within the main texture component grains was principally consistent with the respective Taylor factor values. The microband boundaries corresponded to the expected single slip {111} plane for the A oriented grains while these boundaries for the C oriented grains represented a variety of planes even for a single grain.
- Published
- 2013
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25. New Insights into the Dynamic and Metadynamic Recrystallization of Austenite
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Hodgson, Peter D., Cizek, Pavel, and Beladi, Hossein
- Abstract
The present work provides a summary of the recent findings obtained from the experimental investigation of the grain structure, crystallographic texture and dislocation substructure evolution in an austenitic Ni-30%Fe model alloy during dynamic recrystallization (DRX) and post-dynamic annealing. It has been found that the DRX texture characteristics become increasingly dominated by the low Taylor factor grains during DRX development, which presumably results from the preferred nucleation and lower consumption rates of these grains. The substructure of DRX grains is random in character and displays complex, hierarchical subgrain/cell arrangements characterized by accumulation of misorientations across significant distances. The stored energy within DRX grains appears to be principally consistent with the corresponding Taylor factor values. The changes observed within the fully dynamically recrystallized microstructure during post-dynamic annealing have provided a basis to suggest a novel mechanism of metadynamic softening for the current experimental conditions. It is proposed that the initial softening stage involves rapid growth of the dynamically formed nuclei and migration of the mobile boundaries. The sub-boundaries within DRX grains progressively disintegrate through dislocation climb and dislocation annihilation, which ultimately leads to the formation of dislocation-free grains, and the grain boundary migration gradually becomes slower. As a result, the DRX texture largely remains preserved throughout the annealing process.
- Published
- 2012
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26. Substructure and Texture Characteristics of the Deformed Matrix and Dynamically Recrystallized Grains in a Ni-30%Fe Austenitic Alloy
- Author
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Cizek, Pavel, Beladi, Hossein, and Hodgson, Peter D.
- Abstract
The substructure and crystallographic texture characteristics of both the deformed matrix and dynamically recrystallized (DRX) grains were investigated in a Ni-30%Fe austenitic model alloy subjected to hot torsion. Deformation was performed at a temperature of 1000°C using strain rates of 1, 0.1 and 0.01 s
-1 , which produced a range of DRX grain sizes. Electron back-scattered diffraction and transmission electron microscopy were employed in the investigation. Both the deformed matrix and DRX grains revealed the texture components expected for simple shear deformation by crystallographic slip. The texture of DRX grains was dominated by low Taylor factor components as a result of their lower consumption rate during growth of these grains. There was a marked difference in the substructure characteristics between the deformed matrix and DRX grains regardless of the grain size and orientation. The deformed matrix substructure was largely characterized by organized, banded subgrain arrangements with alternating misorientations. By contrast, the substructure of DRX grains was generally more random in character and displayed complex, more equiaxed subgrain/cell arrangements characterized by local accumulation of misorientations. Based on the experimental observations, a mechanism of the distinct substructure development within DRX grains has been proposed.- Published
- 2012
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27. Effects of mechanical properties on the contact profile in Berkovich nanoindentation of elastoplastic materials
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Wang, Jiangting, Hodgson, Peter D., and Yang, Chunhui
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Abstract
- Published
- 2012
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28. Interfacial Chemistry and Adhesion between Titanium Dioxide Nanotube Layers and Titanium Substrates
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Xiong, Jianyu, Wang, Xiaojian, Li, Yuncang, and Hodgson, Peter D.
- Abstract
Interfacial chemistry and adhesion between titanium dioxide (TiO2) nanotube layers and titanium (Ti) substrates were studied in this Article. TiO2nanotube layers were produced on pure Ti by anodization and annealed in air for different time durations. The adhesion of the TiO2nanotube layers was then investigated by Rockwell C indentation test. Results show that adhesion of TiO2nanotube layers improved with the extension of annealing time. This improvement in adhesion of TiO2nanotube layers was analyzed from the viewpoint of interfacial chemistry using energy dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). It suggests that more Ti−O bonds formed in the interface after annealing, and this led to the improved adhesion of the TiO2nanoube layers.
- Published
- 2011
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29. Biomimetic Modification of Porous TiNbZr Alloy Scaffold for Bone Tissue Engineering
- Author
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Wang, Xiaojian, Li, Yuncang, Hodgson, Peter D., and Wen, Cui'e
- Abstract
Porous titanium (Ti) and Ti alloys are important scaffold materials for bone tissue engineering. In the present study, a new type of porous Ti alloy scaffold with biocompatible alloying elements, that is, niobium (Nb) and zirconium (Zr), was prepared by a space-holder sintering method. This porous TiNbZr scaffold with a porosity of 69% exhibits a mechanical strength of 67 MPa and an elastic modulus of 3.9 GPa, resembling the mechanical properties of cortical bone. To improve the osteoconductivity, a calcium phosphate (Ca/P) coating was applied to the surface of the scaffold using a biomimetic method. The biocompatibility of the porous TiNbZr alloy scaffold before and after the biomimetic modification was assessed using the SaOS2 osteoblast–like cells. Cell culture results indicated that the porous TiNbZr scaffold is more favorable for cell adhesion and proliferation than its solid counterpart. By applying a Ca/P coating, the cell proliferation rate on the Ca/P-coated scaffold was significantly improved. The results suggest that high-strength porous TiNbZr scaffolds with an appropriate osteoconductive coating could be potentially used for bone tissue engineering application.
- Published
- 2010
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30. Deformation mechanisms in an ultra-fine grained Al alloy
- Author
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Sabirov, Ilchat, Barnett, Matthew R., Estrin, Yuri, Timokhina, Ilana, and Hodgson, Peter D.
- Abstract
This work focuses on the deformation behavior of an ultra-fine grained Al-Mg-Si alloy processed by equal channel angular pressing over a wide range of temperatures and strain rates. The effect of temperature and strain rate on the homogeneity of plastic deformation, the evolution of microstructure, the strain rate sensitivity and the underlying deformation mechanisms are investigated. It is demonstrated that the localization of plastic deformation at the micro scale is triggered by grain boundary sliding due to grain boundary diffusion. The contributions of different deformation mechanisms during the plastic deformation of the material are discussed.
- Published
- 2009
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31. Ti6Ta4Sn Alloy and Subsequent Scaffolding for Bone Tissue Engineering
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Li, Yuncang, Xiong, Jianyu, Wong, Cynthia S., Hodgson, Peter D., and Wen, Cui'e
- Abstract
Porous titanium (Ti) and titanium alloys are promising scaffold biomaterials for bone tissue engineering, because they have the potential to provide new bone tissue ingrowth abilities and low elastic modulus to match that of natural bone. In the present study, a new highly porous Ti6Ta4Sn alloy scaffold with the addition of biocompatible alloying elements (tantalum (Ta) and tin (Sn)) was prepared using a space-holder sintering method. The strength of the Ti6Ta4Sn scaffold with a porosity of 75% was found to be significantly higher than that of a pure Ti scaffold with the same porosity. The elastic modulus of the porous alloy can be customized to match that of human bone by adjusting its porosity. In addition, the porous Ti6Ta4Sn alloy exhibited an interconnected porous structure, which enabled the ingrowth of new bone tissues. Cell culture results revealed that human SaOS2osteoblast-like cells grew and spread well on the surfaces of the solid alloy, and throughout the porous scaffold. The surface roughness of the alloy showed a significant effect on the cell behavior, and the optimum surface roughness range for the adhesion of the SaOS2cell on the alloy was 0.15 to 0.35 μm. The present study illustrated the feasibility of using the porous Ti6Ta4Sn alloy scaffold as an orthopedic implant material with a special emphasis on its excellent biomechanical properties and in vitrobiocompatibility with a high preference by osteoblast-like cells.
- Published
- 2009
- Full Text
- View/download PDF
32. Preparation of Bioactive Porous Titanium-Molybdenum Alloy through Powder Metallurgy
- Author
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Yamada, Yasuo, Li, Yun Cang, Xiong, Jian Yu, Banno, Takumi, Hodgson, Peter D., and Wen, Cui E.
- Abstract
Porous Ti-Mo alloy samples with different porosities from 52% to 72% were successfully fabricated by the space-holder sintering method. The pore size of the porous Ti-Mo alloy samples were ranged from 200 to 500 μm. The plateau stress and elastic modulus of the porous Ti-Mo alloy samples increases with the decreasing of the porosity. Moreover, an apatite coating on the Ti-Mo alloy after an alkali and heat treatment was obtained through soaking into a simulated body fluid (SBF). The porous Ti-Mo alloy provides promising potential for new implant materials with new bone tissue ingrowth ability, bioactivity and mechanical properties mimicking those of natural bone.
- Published
- 2009
- Full Text
- View/download PDF
33. INFLUENCE OF POROSITY ON SHAPE MEMORY BEHAVIOR OF POROUS TiNiSHAPE MEMORY ALLOY
- Author
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XIONG, JIANYU, LI, YUNCANG, HODGSON, PETER D., and WEN, CUI'E
- Abstract
Porous Ti-50.5at.%Nishape memory alloy (SMA) samples with a range of porosities were prepared by spacer sintering. The porous structure of the alloy was examined using scanning electron microscopy (SEM). The phase constituents of the porous TiNialloy were determined by X-ray diffraction (XRD). The shape memory behavior of the porous TiNialloy was investigated using loading–unloading compression tests. Results indicate that the porous TiNialloy exhibits superelasticity and the recoverable strain by the superelasticity decreases with the increase of porosity. After a prestrain of 7%, the superelastically recovered strains for the porous TiNialloy samples with porosities of 46%, 59%, 69% and 77% are 2.0%, 1.8%, 1.5% and 1.3%, respectively. The pores in the TiNialloy samples cause stress/strain concentration, as well as crack initiation, which adversely affect the shape memory behavior of the porous TiNialloy.
- Published
- 2008
34. Nanoparticle-mediated ultra grain refinement and reinforcement in additively manufactured titanium alloys
- Author
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Chao, Qi, Mateti, Srikanth, Annasamy, Murugesan, Imran, Mohammad, Joseph, Jithin, Cai, Qiran, Li, Lu Hua, Cizek, Pavel, Hodgson, Peter D., Chen, Ying, Fabijanic, Daniel, and Xu, Wei
- Abstract
Additive manufacturing, also known as 3D printing, overcomes many design and manufacturing constraints to allow almost direct production of metals into complicated geometries. However, coarse columnar grain structures, up to the millimeter-scale, are commonly produced in titanium and its alloys through the layer-by-layer process and this causes significant anisotropy in mechanical properties. Here we report an innovative approach for microstructure refinement of an additively manufactured Ti-6Al-4V alloy via directed energy deposition of boron nitride nanotube (BNNT) decorated powders. With only 0.4 wt% BNNT, this process results in unprecedented grain refinement down to a few micrometers and over 50% strength enhancement. A unique texture-weakened structure comprising fine equiaxed grains is achieved via a novel nanoparticle-mediated nucleation mechanism enabled by local hypereutectic precipitation in the rapid solidification process. This mechanism is highly suited to the metallurgical environment of metal additive manufacturing and creates a pathway for screening effective grain refiners in titanium and other alloy systems.
- Published
- 2021
- Full Text
- View/download PDF
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