Showing papers in "Transactions of The Indian Institute of Metals in 2008"
TL;DR: In this paper, the evolution of texture depends on several factors such as deformation temperature, mode of deformation (rolling, forging and extrusion), initial texture and microstructure, degree and rate of deformations and alloying elements.
Abstract: The purpose of this article is to provide a comprehensive and coordinated review of the evolution of texture during thermomechanical processing of titanium and its alloys. In general, the evolution of texture depends on several factors such as deformation temperature, mode of deformation (rolling, forging and extrusion), initial texture and microstructure, degree and rate of deformation and alloying elements. Phase transformation textures and associated variant selection mechanisms as function of initial texture and heat treatment have also been discussed. The chronological developments of texture modelling and deformation mechanisms in these alloys are presented.
33 citations
21 citations
21 citations
TL;DR: In this paper, the linear coefficients for time, acid concentration and amount of paper were found to be significant for extraction of Cu, Ni, Co and Mn in the presence of a cellulosic reductant, waste newspaper.
Abstract: Sulphuric acid leaching of manganese nodule for extraction of Cu, Ni, Co and Mn in presence of a novel cellulosic reductant, waste newspaper, has been reported. The various parameters chosen for the study were: time, temperature, H2SO4 concentration and amount of paper. To quantify the linear and interaction coefficients a 23 full factorial design of experiments was followed. The regression equations were determined and the adequacy of these equations was tested by Fischer’s test. The linear coefficients for time, acid concentration and amount of paper were found to be significant for extraction of Cu, Ni, Co and Mn. While acid concentration and amount of paper showed positive interactions for Cu, Ni and Co extractions it had negative significance for Mn dissolution. Under the conditions for >97% extraction of metal values iron extraction was ∼40%. In order to reduce the iron contamination by discarding iron as jarosite effect of addition of ammonium sulphate during leaching was also studied. Iron extraction could be brought down to 14% from ∼40% with the addition of 30g/L (NH4)2SO4 without affecting the recoveries of other metals.
18 citations
TL;DR: In this article, a review of the progress made in the development of carbon-containing iron aluminides is presented along with possible directions for future work, along with a detailed assessment of the current state-of-the-art.
Abstract: In the last decade iron aluminide composites containing carbon have been developed through ingot metallurgy routes. Work on Fe-Al alloys containing 15 to 50 atom% Al and up to 16 atom% carbon is reviewed here. Presence of carbon in the alloy may lead to savings in the processing and material costs. It also improves the machinability in ordered iron aluminides. Carbide formation in the iron aluminide matrix results in significant improvements in strength and creep resistance. The work so far has concentrated on alloys with low (<35 atom%) Al-contents based on disordered α-phase and on Fe3Al because at Al-contents of ∼37 atom% or above graphite formation may occur in Fe-Al-C alloys. Alloys containing carbide as the major phase were found to be very brittle. The presence of carbon may limit the role of substitution alloying elements such as Cr, Mo or Ti. It may also affect hydrogen mobility in these alloys which are susceptible to hydrogen induced cracking. These factors are analysed. An assessment of the progress made in development of carbon containing iron aluminides is presented along with possible directions for future work.
16 citations
TL;DR: In this article, the microstructures of Al 6061 and Al 6063 alloys were investigated and the deformation mechanisms of UFG Al alloys contributing to their enhanced strength were discussed.
Abstract: The present work has been focused to investigate the mechanical behavior and microstructural characteristics of cryorolled Al 6063 and Al 6061 alloys. Hardness and tensile tests of the cryorolled Al alloys were carried out to understand its deformation behavior. SEM/EBSD was used to characterise the microstructures of cryorolled Al alloys and observed the formation of ultrafine-grained microstructures in the materials due to severe plastic strain induced during cryorolling. XRD was used to analyse the formation of different phases during cryorolling of the Al alloys. It is evident from the present study that UFG Al alloys exhibit higher hardness and strength when compared to the bulk Al alloys due to the grain size, higher dislocation density and precipitation hardening effect. The cryorolled Al 6061 alloys exhibit higher tensile strength (346 MPa) and hardness (120 Hv) as compared to Al 6063 alloys (Tensile strength: 240MPa and Hardness: 96.5 Hv) in the present investigation. The deformation mechanisms of UFG Al alloys contributing to their enhanced strength are discussed.
16 citations
TL;DR: In this paper, the microstructure properties of Ti5Si3 and its composites have been reviewed with an emphasis on the micro-structure-property relationships, and it is found that the grain size is a critical parameter, and smaller grain sizes are desirable for reducing the magnitude of internal residual stress caused by the crystallographic anisotropy in coefficients of thermal expansion.
Abstract: The demand for materials to be used in the components operating above 1100°C in advanced aero-engines drives the development of the silicide-based intermetallic alloys and composites, including the titanium silicides. The mechanical behaviour of Ti5Si3 and its composites has been reviewed with emphasis on the microstructure-property relationships. It is found that the grain size is a critical parameter, and smaller grain sizes are desirable for reducing the magnitude of internal residual stress caused by the crystallographic anisotropy in coefficients of thermal expansion. The reduction in grain size leads to significant improvement in hardness, room temperature flexural strength and fracture toughness. On the other hand, the high temperature strength observed at slow strain rates and creep resistance are higher in the samples with the coarser grain sizes. Further improvements in the strength, fracture toughness and high temperature creep resistance are possible, either through the development of multiphase alloys, or by the use of ceramic reinforcements in composites.
15 citations
TL;DR: In this paper, an overview of the mechanical properties, corrosion resistance, wear resistance, fatigue resistance and the influence of external and internal parameters on the properties of ECAPed CP-Ti.
Abstract: Equal Channel Angular Extrusion (ECAE) also called as Equal Channel Angular Pressing (ECAP) is an emerging mechanical or thermo mechanical method for synthesis of bulk ultra fine grained or nano materials. The uniqueness of ECAP is that the fine grains are obtained without changing any of the dimensions of the sample. The grain refinement increases the strength of CP-Ti to the strength levels of Ti-6Al-4V, a commonly used material for bio implants. Though Ti-6Al-4V alloys satisfy the biomedical requirements, the Al and V are toxic to human tissue. ECAP is an attracting technique for strengthening commercially pure titanium (CP-Ti) to a level of Ti-6Al-4V since CP-Ti has better compatibility for bio medical applications. Hence, the research is focused on ECAP of CPTi. This overview mainly focuses on the mechanical properties, corrosion resistance, wear resistance, fatigue resistance and the influence of external and internal parameters on the properties of ECAPed CP-Ti. It also highlights the methods employed for increasing the deformability of CP-Ti. Finally, the suitability of ECAP for industrial production is also discussed. The state of the art in this field is encouraging and showing positive signs of commercializing ECAP of CP-Ti in the near future.
13 citations
TL;DR: In this article, four new rail steel compositions, with different combinations of microalloying elements Cu, Cr, Ni and Si, were designed and processed as per the thermomechanical schedule for normal rail steel processing in industry.
Abstract: Eutectoid steels, which are traditionally used as rails in railway systems, are prone to corrosion, especially in coastal environments. In order to minimize this problem, four new rail steel compositions, with different combinations of microalloying elements Cu, Cr, Ni and Si, were designed and processed as per the thermomechanical schedule for normal rail steel processing in industry. Corrosion behavior of the rail steels were studied by weight loss measurement after immersion test and Tafel polarization in freely aerated 3.5 % NaCl. The rust obtained after immersion test were characterized by Fourier transform infrared spectroscopy (FTIR). Corrosion rate obtained weight loss measurement was similar for all the rail steels. γ-FeOOH (lepidocrocite) and δ-FeOOH were identified as the major rust phases from the FTIR spectra of the rail steels. The relative absorption intensities of these rust phases were similar for all the rail steels. Corrosion rates calculated from Tafel polarization tests were similar for all the rail steels. The corresponding free corrosion potentials were also similar for all the rail steels. The zero corrosion potential obtained from Tafel polarization of Cu-Mo, Cr-Mn, Cu-Ni, Cr-Cu-Ni and Cr-Cu-Ni-Si rail steels was more noble compared to C-Mn and Cu-Si rail steels indicating better corrosion resistance of these alloys. The importance of conducting alternate wetting and drying test has been emphasized.
12 citations
TL;DR: In this paper, the feasibility of using the Repetitive Bending and Straightening (RBS) process to improve the mechanical properties of commercial purity aluminium has been investigated, which was carried out by bending with a U-bending die of 10 mm radius followed by straightening between flat dies.
Abstract: The feasibility of using the Repetitive Bending and Straightening (RBS) process to improve the mechanical properties of commercial purity aluminium has been investigated. RBS was carried out by bending with a U-bending die of 10 mm radius followed by straightening between flat dies. The ultimate tensile strength (UTS) and yield strength (YS) slightly increased with increasing number of passes. The maximum UTS of 84 MPa and YS of 68 MPa were obtained after four passes and % elongation to failure decreased from 46% to 35% after four passes. The RBS processed Al showed poor improvement in mechanical properties as compared to other SPD processes. Repetitive bending and straightening process is therefore not an effective process to introduce fine grained structures in metals or alloys.
12 citations
TL;DR: In this article, the effect of aging (T-6 treatment) on the corrosion behaviour as well as corrosion inhibition of 6061Al-SiC composite was dealt with. But, the results indicate that both the organic compounds act as anodic inhibitors and are moderately effective in inhibiting the corrosion of 60 61AlSiC(p) composite.
Abstract: Addition of reinforcements like SiC to aluminium matrix has been reported to decrease the corrosion resistance of the matrix due to several reasons, one of them being the galvanic action between the reinforcement and the matrix. Aging of aluminium alloys can also have similar effects as aging results in precipitation of intermetallics. The work deals with effect of aging (T-6 treatment) on the corrosion behaviour as well as corrosion inhibition of 6061Al-SiC composite. Corrosion behaviour of 6061 Al-SiC(p) composite were determined in HCl by Tafel extrapolation technique in the temperature range of 30°C–50°C. Further, the inhibition studies were made using two inhibitors viz. (i) Allyl Thiourea and (ii) Glycyl Glycine. The results indicate that both the organic compounds act as anodic inhibitors and are moderately effective in inhibiting the corrosion of 6061Al-SiC(p) composite. The inhibition efficiency increases with increase in inhibitor concentration. Similar inhibition studies were made on the aged samples. However, in the case of T-6 treated samples, the inhibition efficiency was found to be poor compared to the non-heat treated samples.
TL;DR: In this article, the effects of ball burnishing parameters on the surface hardness of HSLA dualphase steel specimens were investigated based on 34 factorial design and statistical analysis of the results showed that the speed, feed, lubricant and ball diameter have significant effect on surface hardness.
Abstract: Burnishing is used increasingly as a finishing operation which gives additional advantages such as increased hardness, fatigue strength and wear resistance. Experimental work based on 34 factorial design was carried out to establish the effects of ball burnishing parameters on the surface hardness of HSLA dualphase steel specimens. Statistical analysis of the results shows that the speed, feed, lubricant and ball diameter have significant effect on surface hardness.
TL;DR: In this paper, the authors studied the oxidation and corrosion resistance of TiAl3 coatings on various types of substrates, including high speed steel, stainless steel 304 and stainless steel 316, copper and aluminum substrates.
Abstract: Titanium aluminides based on TiAl, TiAl3 and Ti3Al are potential materials for high temperature aerospace applications. Their low density, high temperature creep resistance, high temperature strength and high oxidation resistance make them excellent coating materials. However these coatings are likely to be subjected to high temperature and corrosive environments during service. Hence it is aimed to study the oxidation and corrosion resistance of TiAl3 coatings on various types of substrates. In the present work, TiAl3 is coated on high speed steel, stainless steel 304, stainless steel 316, copper and aluminum substrates by physical vapor deposition technique. X-ray diffraction analysis confirms the presence of TiAl3 phase. The hardness studies reveal that better hardness can be achieved with thick coatings. The oxidation behavior of the coatings is studied by carrying out step stress experiments at elevated temperatures. Coated samples are heated up from 400°C in the steps of 100°C for 1h in each step to 1000°C. The mass gain caused by oxidation was determined. The oxidation curve drawn as a function of mass gain versus temperature reveals that TiAl3 film started to oxidize above 800°C, where as oxidation of the uncoated substrates began at a much lower temperature of 550°C. The excellent oxidation resistance of the coatings can be attributed to the formation of an amorphous Al2O3 film. Scanning electron microscope (SEM) and EDAX analysis confirm the presence of an amorphous Al2O3 film. The corrosion behavior of TiAl3 coatings are investigated by the polarization resistance experiments in NaCl aqueous solution at ambient temperature. According to the Tafel plot analysis, the coatings show lower corrosion rate than the untreated substrates. The major corrosion in the coatings arose from electrolyte penetration into the pores of the coatings. In fact, a dense coating showed a high corrosion resistance in an aqueous medium.
TL;DR: An overview of the developments in NiTi shape memory alloys can be found in this article, where the shape memory effect (SME) and superelasticity (SE) of NiTi SMA are discussed.
Abstract: Shape memory alloys (SMAs) are a special class of metallic materials which respond with a considerable change in their properties to small changes in temperature or stress. The SMAs offer two interesting characteristics, viz., shape memory effect (SME) and superelasticity (SE), also called pseudoelasticity which make them attractive for applications in engineering and biomedical fields. Among the various SMAs, NiTi base alloys have been the most commercially exploited ones because of their superior SME and SE, mechanical properties, corrosion resistance and biocompatibility. Since the pioneering discovery of NiTi SMA in early 1960s, significant progress has been made in the processing and understanding of the behaviour of these alloys. In spite of these efforts, the NiTi SMAs continue to offer challenges to the scientists and engineers, and new findings are being made continuously. This paper provides an overview of the developments in NiTi SMAs.
TL;DR: In this paper, the efficacy of shelled Moringa oleifera seeds (SMOS) in decontaminating Cd(II) and Pb (II) ions from aqueous environment both present as single metal and as binary metal solution was highlighted.
Abstract: Ever-growing list of chemical contaminants released into the environment through excessive industrialization on a large scale includes numerous chemical pollutants more prominently heavy metals. The discharge of heavy metals in aqueous system and their removal have been a challenging task for environmentalists for last one decade. Keeping these views in mind, the present study highlights the efficacy of shelled Moringa oleifera seeds (SMOS) in decontaminating Cd (II) and Pb (II) ions from aqueous environment both present as single metal and as binary metal solution. The extent of adsorption capacity for Cd (II) and Pb (II) on Moringa oleifera seeds for binary metal ions [76.59% and 81.10%] was found to be low as compared to single metal ions [85.10% and 96.10%]. Morphological changes observed in Scanning Electron Micrographs of native and treated SMOS indicates the existence of biosorption phenomenon. Fourier Transform Infrared Spectrometry of the exhausted seed biomass highlights amino acids-metal interaction responsible for sorption phenomenon. The sorption capacity of regenerated biomass remained almost constant after three cycle of sorption suggesting that the lifetime cycle was sufficient for continuous application.
TL;DR: In this article, a single-phased copper alloy containing 10 wt% Ni, 29 Wt% Zn, up to 5 Wt % Mn and 1 wt % Fe was developed for seawater applications.
Abstract: Cu-10Ni alloy is a standard material for seawater application. Under Indian scenario, where half of copper and whole of Ni (and Cu-Ni) requirement is met by imports, search for a cheaper substitute is obvious. An attempt has been made to develop a single-phased copper alloy containing 10 wt% Ni, 29 wt% Zn, up to 5 wt% Mn and 1 wt% Fe as a substitute to Cu-10wt% Ni-1wt% Fe alloy. Studies on Corrosion resistance of test alloys were carried out in synthetic seawater (ASTM D 114-75) by electro-chemical methods (cathodic and anodic polarization). Corrosion product film formed on alloy containing 5wt% Mn was characterized by SEM and XRD. A film of Cu2O was found to form on the surface of the alloy, which accords corrosion protection. The test alloys containing 29 wt% Zn and 3 or 5 wt% Mn have exhibited better corrosion resistance in synthetic seawater than Cu-10Ni alloy. The role of Mn and Zn addition has been discussed.
TL;DR: In this paper, the structure and mechanical properties of a metastable β titanium alloy were investigated in different heat treatment conditions, and the alloy was melted by consumable vacuum arc melting followed by conventional forging and rolling.
Abstract: Microstructure and mechanical properties of a metastable β titanium alloy were investigated in different heat treatment conditions. The alloy was melted by consumable vacuum arc melting followed by conventional forging and rolling. Microstructure and mechanical property evaluation were carried out in solution treatment and three different aging conditions. While low temperature aging resulted in increase in strength and decrease in ductility as compared to solution treatment condition, a double aging cycle provided considerably higher elongation values with a marginal increase in strength. Maximum fracture toughness was obtained in the double aging condition.
TL;DR: In this article, a laser nitriding was performed using Nd: YAG laser to enhance the corrosion resistance of Titanium and Ti-13Nb-13Zr alloys.
Abstract: C.P. Titanium and Ti-13Nb-13Zr alloys are widely used in biomedical applications as dental and orthopedic implants. However these materials are vulnerable to Surface corrosion. The aim of this investigation is to enhance the corrosion resistance of the above alloys through laser nitriding technique. Laser nitriding was performed using Nd: YAG laser. The Electrochemical properties of nitrided layer will be investigated in simulated body solution using potentiodynamic polarization technique. The results will be compared with those obtained on untreated alloys tested in same conditions. The laser nitrided and the corroded samples will also be characterized using XRD and SEM. The enhancement of wear resistance of the above samples will also be presented in this paper.
TL;DR: In this paper, the work done for the indigenous development of Ti-64 ring forgings of various sizes for Kaveri engine has been presented, as per the release specification.
Abstract: Titanium base alloy-Ti-6Al-4V [Ti-64] is extensively used in aero gas turbine [Kaveri engine] for various applications. Majority of the wrought Ti-64 components in the engine are processed through ring rolling/ forging route. Indigenous development and productionisation of the ring forgings have been carried out using the ring rolling mill and allied forging facilities of M/s HAL (F&F), Bangalore / M/s Echjay Industries, Rajkot. Type certified indigenous Ti-64 forging stock [of size up to 250mm diameter] from M/s Mishra Dhatu Nigam Ltd. [MIDHANI], Hyderabad has been used for the development and subsequent productionisation. Satisfactory metallurgical and mechanical properties have been achieved in Ti-64 alloy ring forgings, as per the release specification. Total 79 batches of 29 varieties of the Ti-64 ring forgings for Kaveri engine have been indigenously produced and supplied. This paper presents details of the work done for the indigenous development of Ti64 ring forgings of various sizes for Kaveri engine.
TL;DR: In this paper, tensile tests were performed with select interruptions on pre-polished specimens to study the effects of stress triaxiality on damage micromechanisms operative in IMI-834 titanium alloy.
Abstract: In the present investigation, tensile tests were performed with select interruptions on pre-polished specimens to study the effects of stress triaxiality on damage micromechanisms operative in IMI-834 titanium alloy.
TL;DR: In this article, the oxide scales formed on the surface of the superalloys were characterised by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive Xray spectroscopy (EDAX) analyses.
Abstract: Oxidation behavior of Ni- and Fe- based superalloys has been studied in air at 900°C under cyclic conditions. The mass change measurement with time was used to establish the oxidation kinetics. The oxide scales formed on the surface of the superalloys were characterised by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX) analyses. The oxide scales formed on the superalloys contained NiO, Cr2O3 and Fe2O3. The scales were adherent and only microspalling was observed. Superfer 800 has provided best resistance to oxidation among the alloys studied.
TL;DR: In this paper, high-pressure die-casting (HPDC) is used to produce magnesium alloy castings, which are used in automotive, aerospace, and electronics industries.
Abstract: Magnesium alloy castings are increasingly used in automotive, aerospace and electronics industries. These castings are mainly produced via high-pressure die-casting (HPDC). During this casting process, molten alloy solidifies within a rigid mold, which resists the alloy’s volumetric contraction. As a result, thermal and mechanical stresses develop in the casting and potentially lead to the nucleation of hot tears.
TL;DR: In this article, the effect of deformation and heat treatment on the microstructure and mechanical properties of a duplex stainless steel was investigated. And the results showed that cold deformed and heat treated steel exhibits best combination of strength and ductility among all the investigated steel samples.
Abstract: Present study concerns the effect of deformation and heat treatment on the microstructure and mechanical properties of a duplex stainless steel. While hot rolling causes the coarse distribution of the constituent phases (ferrite and austenite), 50% cold rolling results into the elongated and splintered two — phase structure. Supersaturated ferrite structure established by water quenching from 1300°C results into the strengthening due to the formation of fine dispersed austenite precipitates within ferrite grain after isothermal heat treatment (1000°C, 0.5 hour). Duplex structure consisting of ferrite and austenite in a fine-grained form is obtained after isothermal heat treatment of cold rolled sample. Cold deformed and heat treated steel exhibits best combination of strength and ductility among all the investigated steel samples.
TL;DR: In this article, an interrelationship of modulus of elasticity with graphite nodule counts, nodule size and graphite volume has been investigated, and a significant relationship is observed between the modulus and the above mentioned morphological characteristics of graphite.
Abstract: The modulus of elasticity (Young’s Modulus) of cast irons is known to be a function of graphite volume fraction in the microstructure. Low carbon equivalent ductile iron is a low carbon cast iron in which, carbon is present as graphite in nodular form. It is observed that the modulus of elasticity of these irons is higher than that of conventional ductile iron. In the present investigation, an interrelationship of modulus of elasticity with graphite nodule counts, nodule size and graphite volume has been investigated. A significant relationship is observed between the modulus of elasticity and the above mentioned morphological characteristics of graphite.
TL;DR: In this paper, the corrosion behavior of weld metal, partially melted zones and heat affected zones of gas tungsten arc welds in A356 Al-Si alloy with different prior thermal tempers has been studied.
Abstract: The corrosion behaviour of weld metal, partially melted zones and heat affected zones of gas tungsten arc welds in A356 Al-Si alloy with different prior thermal tempers has been studied. Continuous and pulsed current gas tungsten arc welding techniques were used. Potentiodynamic polarization testing was carried out to determine the corrosion resistance. Optical and scanning electron microscopy studies were carried out to determine the corrosion mechanism. The partially melted zone of the welds was found to be attacked severely. A pulsing technique was found to decrease the severity of corrosion damage in the partially melted zone. The prior thermal condition of the alloys was found to influence the corrosion of heat affected zones of welds.
TL;DR: Differential scanning calorimetric (DSC) studies have been carried out at different heating rates to examine the solid state reactions in a 7017 Al-Zn-Mg alloy of water-quenched (WQ) state and artificial aged tempers as discussed by the authors.
Abstract: Differential scanning calorimetric (DSC) studies have been carried out at different heating rates to examine the solid state reactions in a 7017 Al-Zn-Mg alloy of water-quenched (WQ) state and artificial aged tempers. All the exothermic and endothermic peaks of the thermograms indicating the solid state reaction sequence have been identified and discussed. The shifting of peak temperatures of all the reactions to higher temperatures with increasing heating rates suggests that the reactions are thermally activated and kinetically controlled. The variations of hardness with aging time at an artificial aging temperature have also been studied to obtain the under-, peak- and over aged tempers. The fraction of transformation (Y), the rate of transformation (dY/dt), the transformation function f(Y) and the kinetic parameters such as activation energy (Q) and frequency factor (k0) of the solid state reactions in the alloy have been determined by analyzing the DSC data i.e. heat flow involved with the corresponding DSC peaks. It has been found that the kinetic parameters of the solid state reactions are in good agreement with the published data.
TL;DR: In this paper, a new high strength Ti-15-3 (metastable beta) alloy is developed, offering advantage of amenability to cold forming and attainment of very high strength through aging.
Abstract: Indian Space programs require high specific strength materials with compatibility to various working fluids/environments. Titanium alloys possess these characteristics and hence are materials of choice for various space applications like high pressure gas bottles and upper stage propellant tanks of launch vehicles and satellites. For these applications, main contribution is from the workhorse two phase (α+β) Ti-6Al-4V alloy, which is used in annealed as well as STA (solution treated and aged) conditions. Further, application at extremely low temperature of 20K requires a special grade single phase (α) Ti-alloy, namely Ti-5Al2.5Sn-ELI (extra Low Interstitial). For these two alloys, processing techniques required for fabrication of various components is established through closed-die forging / plate-forming / ring rolling, machining and EB welding. Close control on the processing parameters are mandatory to achieve desired microstructure, mechanical properties and cost effective components. Indigenous development of a new high strength Ti-15-3 (metastable beta) alloy is accomplished, offering advantage of amenability to cold forming and attainment of very high strength through aging. This can lead to processing of lighter, cost effective and near net shape components and thin-sheet-structures.
TL;DR: In this article, a 3D simulation of ECAP process was carried out for different inner corner radii for strain hardening aluminium alloy (AA 6101) with cylindrical cross section.
Abstract: Equal Channel Angular Pressing (ECAP) is currently being widely investigated because of its potential to produce ultrafine grained microstructures in metals and alloys. A sound knowledge of the plastic deformation and the strain distribution is necessary for understanding the relationships between strain inhomogeneity and geometry of die. Considerable research has been reported on finite element analysis of this process, assuming 2D plane strain condition. The 2D models are not suitable due to the component geometry, especially for work-piece with cylindrical cross section. In the present work 3D simulation of ECAP process was carried out for different inner corner radii for strain hardening aluminium alloy (AA 6101). Strain inhomogeneity is presented and discussed for all cases. Pattern of strain variation along certain radial lines in the body of work-piece is presented.
TL;DR: In this article, an alloy of Titanium with 5% Tantalum and 1.8% Niobium has been developed which possesses high corrosion resistance in highly oxidising environments and the microstructural basis that enabled design of optimum thermo-mechanical treatments has been established for this alloy.
Abstract: An alloy of Titanium with 5% Tantalum and 1.8% Niobium has been developed which possesses high corrosion resistance in highly oxidising environments. The microstructural basis that enabled design of optimum thermo-mechanical treatments has been established for this alloy. The classification of the alloy, transformation temperatures and different types of phase transformations were evaluated for the first time by experimental methods like metallography and calorimetry and empirical methods. Systematic microstructural modifications were introduced by thermo-mechanical treatments to improve corrosion resistance and mechanical properties. The Ti-5Ta-1.8Nb alloy exhibited interesting texturing behaviour. Deformation and transformation textures exhibited during unidirectional cold rolling and subsequent β→α+β transformation were studied using XRD and Electron Back Scatter Diffraction techniques. The cross section of a wire drawn specimen exhibited (1 0–1 0)α texture while a cold rolled specimen showed (0 0 0 2)α deformation texture along the length — width direction. The transformation texture by itself was found to be dependent on the type of deformation texture, (1 1 −2 0)α in cold rolled and (1 1 −2 2)α texture in the case of wire drawn alloy. A new method has been proposed to determine theoretical misorientation angle and axis between variants of hcp a product transforming from a parent bcc crystal, obeying Burgers Orientation Relationship. The role of variant selection mechanisms in the final texture of the alloy has been demonstrated by comparison of texture maps obtained by X-ray Diffraction with those computed.
TL;DR: In this article, a disc shape spray form castings were made of Al-6.91Si and Al-10.1Si alloys, and then their shape, wear and mechanical properties were studied.
Abstract: Manufacturing process through spray forming leads to give near-net-shape and fine grain microstructure. In this process Si particles, which are not distributed uniformly in conventional casting process, are distributed uniformly throughout the casting. In the present study disc shape spray form castings were made of Al-6.91Si and Al-10.1Si alloys, and then their shape, wear and mechanical properties were studied. The shape of the deposit was observed to be the most uniform at 30o inclination angle of the substrate. The hardness and tensile strength value of spray formed alloys shows the increment in the mechanical property in contrast to as cast alloys. The wearing properties of Al-10.1Si alloy were found to be better than that of the Al-6.91Si alloy.