Papers by Venkata Anumalasetty
Materials Science and Engineering: C, 2017
Materials Science and Engineering: C, 2017
Combined effect of grain refinement and surface modification of pure titanium on the attachment o... more Combined effect of grain refinement and surface modification of pure titanium on the attachment of mesenchymal stem cells and osteoblast-like SaOS-2 cells,
Corrosion Science, 2009
The corrosion of commercial die-cast Mg-Al alloys was elucidated by a study, of the corrosion in ... more The corrosion of commercial die-cast Mg-Al alloys was elucidated by a study, of the corrosion in 3% NaCl, of (i) high-pressure die-cast (HPDC) model Mg-Al alloys, (ii) low-purity Mg, (iii) high-purity (HP) Mg and (iv) HP Mg heat treated at 550°C. HPDC is the most important route for the production of Mg components. The corrosion of the model alloys was dominated by the Fe impurity element. The present research identified the appearance of the Fe-rich particles in the microstructure. In high magnification ($1000Â to 5000Â) secondary electron images, they appear as small white features, typically less than 1 lm in diameter. In order to understand the impurity tolerance limits, (i) the appropriate corrosion literature was summarised and reviewed and (ii) Mg phase diagrams were calculated using the Pandat software package. Calculated phase diagrams can explain (i) the tolerance levels for Fe and Cu and (ii) the production of high-purity castings by means of control of melt conditions; this has high significance for the production of quality castings from recycled Mg. A full analysis requires that the Mg database be extended to include Ni, Co and some RE. The Fe tolerance limit is $5-10 ppm for cast HP Mg heat treated at 550°C. Analysis of the Mg corrosion literature indicates that several studies have been dominated by the Fe impurity content and have not dealt with the stated aims; it means that the full chemical composition should be reported in all studies of the corrosion of Mg alloys.
IOP Conference Series: Materials Science and Engineering, 2014
ABSTRACT Ultrafine-grained (UFG) Ti alloys have potential applications in osteosynthesis and orth... more ABSTRACT Ultrafine-grained (UFG) Ti alloys have potential applications in osteosynthesis and orthopedics due to high bio-compatibility and increased weight-to- strength ratio. In current study, Ti6Al7Nb ELI alloy is processed through equal channel angular pressing-conform (ECAP-Conform) and subsequent thermomechanical processing to generate a UFG microstructure. The fatigue properties of UFG alloys are compared to coarse grained (CG) alloys. Our study demonstrates that the UFG alloys with an average grain size of ~180 nm showed 35% enhancement of fatigue endurance limit as compared to coarse-grained alloys. On the fracture surfaces of the UFG and CG samples fatigue striations and dimpled relief were observed. However, the fracture surface of the UFG sample looks smoother; fewer amounts of secondary micro-cracks and more ductile rupture were also observed, which testifies to the good crack resistance in the UFG alloy after high-cyclic fatigue tests.
Journal of the Mechanical Behavior of Biomedical Materials, 2016
Surface modification techniques are widely used to enhance the biological response to the implant... more Surface modification techniques are widely used to enhance the biological response to the implant materials. These techniques generally create a roughened surface, effectively increasing the surface area thus promoting cell adhesion. However, a negative side effect is a higher susceptibility of a roughened surface to failure due to the presence of multiple stress concentrators. The purpose of the study reported here was to examine the effects of surface modification by sand blasting and acid-etching (SLA) on the microstructure and fatigue performance of coarse-grained and ultrafine-grained (UFG) commercially pure titanium. Finer grain sizes, produced by equal channel angular pressing, resulted in lower values of surface roughness in SLA-processed material. This effect was associated with greater resistance of the UFG structure to plastic deformation. The fatigue properties of UFG Ti were found to be superior to those of coarse-grained Ti and conventional Ti-6Al-4V, both before and after SLA-treatment.
Severe plastic deformation (SPD) processed ultrafine grain (UFG) Ti has been receiving much atten... more Severe plastic deformation (SPD) processed ultrafine grain (UFG) Ti has been receiving much attention by biomedical industry due to its excellent mechanical and physical properties. In addition, the biomedical industry is paying special attention to the commercially pure titanium (CP-Ti) with low iron. However, there is a scarcity of readily accessible public literature to explain the reasons for choosing CP-Ti with low iron for biomedical applications. Hence, in current study detailed microstructure and mechanical property characterization of coarse grain (CG) Ti and UFG MITHRALMAX® CP-Ti (ASTM Grade 4) with various iron contents, plus other compositional variations, has been carried out. Ti with low iron content showed wider spread in grain size in both CG and UFG conditions. However, the Ti with medium and high iron contents showed more uniform grain structure in both CG and UFG conditions. Ti with medium iron content showed enhanced tensile properties compared to Ti with low and...
Equal channel angular pressing (ECAP) is the most promising severe plastic deformation (SPD) tech... more Equal channel angular pressing (ECAP) is the most promising severe plastic deformation (SPD) technique for fabrication of bulk ultrafine grain materials, compaction of powders nearer to theoretical density, and property enhancement of tubular materials.
ABSTRACT Various techniques of severe plastic deformation (SPD) are used with the purpose of fabr... more ABSTRACT Various techniques of severe plastic deformation (SPD) are used with the purpose of fabricating bulk ultrafine grain materials and for the compaction of advanced powders. Equal channel angular extrusion/pressing (ECAE/ECAP), which is one of the SPD techniques, has unique ability to generate huge strains, high strain rates, absence of shape change, and minimal load requirements. ECAE has thus been used for enhancing the microstructure and mechanical properties of tubular materials as well as for compaction of powders through the powder in tube (PIT) technique. Compared to the conventional metal forming techniques like extrusion, rolling and drawing, this process has many advantages: unidirectional deformations can be produced under relatively low pressures and loads in massive products, and it also promotes the formation of equi-axed grains with high-angle grain boundaries. DOCTOR OF PHILOSOPHY (SME)
Advanced Engineering Materials, 2016
High fatigue strength is one of the major requirements for dental implant materials. It was previ... more High fatigue strength is one of the major requirements for dental implant materials. It was previously shown that the fatigue strength under conventional stress-control tension–compression testing can be doubled for commercially pure (CP) titanium processed by equal channel angular pressing. However, the fatigue endurance of an implant exposed to cyclic loading in corrosive media (bodily fluids) may potentially be compromised. In this work, non-conventional bending fatigue testing in air and in simulated body fluid (SBF) has been carried out for coarse-grained and ultrafine-grained CP titanium.
Journal of Materials Processing Technology, 2016
Abstract Application of damage model in combination with finite element analysis to design and op... more Abstract Application of damage model in combination with finite element analysis to design and optimization of equal channel angular pressing—conform of commercially pure titanium against ductile failure is demonstrated. The properties required for precise simulation of the process and prediction of damage accumulation (equivalent stress as function of equivalent strain and temperature and low bound ductility function) are obtained in the temperature interval 20–400 °C and described in details.
Materials Science Forum, 2007
Binary Mg-Al alloys with varying content of aluminium from 0.5 to 12mass% have been studied. The ... more Binary Mg-Al alloys with varying content of aluminium from 0.5 to 12mass% have been studied. The proof stress increase in two steps whereas the ductility exhibits two correlated stepwise drops, as the aluminium content increases. The first increase in strength, and attendant drop in ductility, is observed between 4 and 5 mass% Al. The second stepwise change is observed between 10 and 12 mass% Al. These effects are connected with well defined changes in the microstructure: at 4 mass% a dispersion of β-phase intermetallic particles appears in the core region and a closed cell structure develops near the surface; at 12 mass% Al, the increased volume fraction of the β- phase intermetallics extends the interconnected network of intermetallics to include the core region as well. The micromechanics of the strengthening and decreased ductility are discussed.
Microhardness cross sectional maps of cast-to-shape tensile specimens of thickness 1 and 5 mm hav... more Microhardness cross sectional maps of cast-to-shape tensile specimens of thickness 1 and 5 mm have been determined for a Mg-12%AI binary alloy. For the 5 mm thick specimen the hardness was generally higher near the surface and at the corners of the cross-section in comparison with that at the centre. This difference was accounted for by the coarser solidification microstructure and the concentration of porosity at the casting's core. In contrast, no large differences in hardness were found across the section for the 1 mm thick specimen. The mapping showed a more or less well defined harder surface layer, albeit discontinuous and asymmetrical, for the 5 mm specimen but little differentiation of the skin for the 1 mm specimen. For both specimens the hardness appeared patchy and non uniform over the entire cross section. These features of the microhardness maps are largely explained by the non uniformity of the grain microstructure.
Scanning Electron Microscope (SEM) and DUalBeam FIB (Focussed Ion Beam) were used to characterize... more Scanning Electron Microscope (SEM) and DUalBeam FIB (Focussed Ion Beam) were used to characterize the intermetallic microstructure in 2D and 3D, respectively. The intermetallic appears as a closely interconnected network with very fine scale near the surface, while it takes a more open structure in the core regions of the casting. The possible effects of this difference in the scale of the intermetallic structure on the mechanical behaviour of the material are discussed.
Equal channel angular pressing (ECAP) is the most promising severe plastic deformation (SPD) tech... more Equal channel angular pressing (ECAP) is the most promising severe plastic deformation (SPD) technique for fabrication of bulk ultrafine grain materials, compaction of powders nearer to theoretical density, and property enhancement of tubular materials.
Magnesium-aluminium. alloys, with varying content of aluminium from 0.5 to 12mass%, have been stu... more Magnesium-aluminium. alloys, with varying content of aluminium from 0.5 to 12mass%, have been studied. With increase in aluminium content, the proof stress increased in two steps whereas the ductility exhibits correlated stepwise drops. The first increase in strength, and corresponding drop in ductility, are observed between 4 and 5 mass% Al. The second stepwise changes are observed between 10 and 12 mass% Al. These effects are connected with well defined changes in the microstructure: at 4.37 mass% small and large volume fraction of P-phase intermetallic particles appears in the core and surface regions, respectively along with eutectic network. At 11.6 mass% Al, the beta-phase interconnected network of intermetallics is developed at both die core and surface regions. The micromechanics of the strengthening and decrease in ductility are discussed.
Materials Letters, 2015
ABSTRACT This study contrasts the extent to which laboratory and industrial scale variants of equ... more ABSTRACT This study contrasts the extent to which laboratory and industrial scale variants of equal channel angular pressing (ECAP) impart desirable microstructures and mechanical properties in Grades 2 and 4 titanium. Industrial-scale ECAP-Conform (ECAP-C) with post-ECAP thermo-mechanical processing (TMP) enhanced performance levels beyond those achieved with the same material processed in the laboratory by ECAP only. ECAP-C processed titanium demonstrated exceptional tensile properties and fatigue strength, superior even to conventional Ti-6Al-4V.
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Papers by Venkata Anumalasetty