- Professor Raman Singh’s primary research interests are in the relationship of Nano-/microstructure and Environment-a... moreProfessor Raman Singh’s primary research interests are in the relationship of Nano-/microstructure and Environment-assisted degradation and fracture, and Nanotechnology for Advanced Mitigation of such Degradations, advanced materials (e.g., graphene) for corrosion mitigation, stress corrosion cracking, and corrosion and corrosion-mitigation of magnesium alloys. Prof Singh’s professional distinctions and recognitions include: over 200 peer-reviewed international journal publications, 15 book chapters/books and over 100 reviewed conference publications, and 4 Discovery, 7 Linkage and an ITRH grant of Australian Research Council. He has supervised 38 PhD students, who came from different disciplines (Mechanical, Chemical, Materials and Mining Engineering, and Science) as well as from different cultural backgrounds (Australian, Middle-eastern, Chinese, Malaysian, Indian, African, North American and Israeli).edit
Research Interests:
ABSTRACT This article presents a novel finding of the role of twinning-induced plasticity (TWIP) in environment-assisted cracking (EAC). TWIP alloys are becoming increasingly attractive for remarkable combination of strength and... more
ABSTRACT This article presents a novel finding of the role of twinning-induced plasticity (TWIP) in environment-assisted cracking (EAC). TWIP alloys are becoming increasingly attractive for remarkable combination of strength and ductility. EAC of a high-manganese TWIP steel was investigated in a passivating environment, to understand the combined role of the frequent localized deformation due to dynamic twinning and quick establishment of surface oxide layer. Here, we show a new mechanism where localized formation of twin bands facilitates EAC.
Research Interests:
Research Interests:
A torsion test has been devised that provides for plane strain constraint in small specimens during fracture toughness testing. This method has been extended for stress-corrosion cracking and a simple torsion load frame has been built to... more
A torsion test has been devised that provides for plane strain constraint in small specimens during fracture toughness testing. This method has been extended for stress-corrosion cracking and a simple torsion load frame has been built to provide for step loading of the specimens. This paper describes using the torsion technique to measure KISCC for aluminum alloy 7075 having two thermo-mechanical treatments.
Research Interests:
The cold spray process is governed by the impact of high velocity feedstock particles onto a substrate without melting. Hence, the bulk material properties are retained. However, it is challenging to achieve good adhesion strength. The... more
The cold spray process is governed by the impact of high velocity feedstock particles onto a substrate without melting. Hence, the bulk material properties are retained. However, it is challenging to achieve good adhesion strength. The adhesion strength depends on factors such as the cold spray process parameters, substrate conditions, coating/substrate interactions at the interface and feedstock material properties. This review examines fundamental studies concerning the adhesion mechanisms of cold spray technology and considers the effect of cold spray input parameters such as temperature, stand-off-distance, pressure, process gas, spray angle, and traverse speed of the cold spray torch on the bonding mechanism and adhesion strength. Furthermore, the effects of substrate conditions such as temperature, hardness, roughness and material on the adhesion mechanism are highlighted. The effect of feedstock properties, such as feed rate, shape and size are summarized. Understanding the e...
Research Interests:
Research Interests:
Research Interests:
Research Interests: Materials Science, Metallurgy, Corrosion, Magnesium, Coating, and 3 moreAlloy, Silane, and Magnesium Alloy
Research Interests: Materials Science, Metallurgy, Corrosion, Magnesium, Coating, and 3 moreAlloy, Silane, and Magnesium Alloy
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Structural changes during the deformation-induced synthesis of nanocrystalline Fe-10Cr-3Al alloy powder via high-energy ball milling followed by annealing and rapid consolidation by spark plasma sintering were investigated. Reduction in... more
Structural changes during the deformation-induced synthesis of nanocrystalline Fe-10Cr-3Al alloy powder via high-energy ball milling followed by annealing and rapid consolidation by spark plasma sintering were investigated. Reduction in crystallite size was observed during the synthesis, which was associated with the lattice expansion and rise in dislocation density, reflecting the generation of the excess grain boundary interfacial energy and the excess free volume. Subsequent annealing led to the exponential growth of the crystallites with a concomitant drop in the dislocation density. The rapid consolidation of the as-synthesized nanocrystalline alloy powder by the spark plasma sintering, on the other hand, showed only a limited grain growth due to the reduction of processing time for the consolidation by about 95% when compared to annealing at the same temperature.
Research Interests:
In the present study, combinations of a Phosphonato silane DEPETES with MTEOS silane, in various ratios were applied on Mg6ZnCa alloy. The coating morphology was characterized using scanning electron microscopy (SEM) and hydrogen... more
In the present study, combinations of a Phosphonato silane DEPETES with MTEOS silane, in various ratios were applied on Mg6ZnCa alloy. The coating morphology was characterized using scanning electron microscopy (SEM) and hydrogen evolution and pH variation of the samples were studied. The results showed that the sol-gel coatings reduced the hydrogen evolution rate of the magnesium alloy inm-simulated body fluid (m-SBF) solution. Moreover, biological response like cell attachment on the coated sample was found to be enhanced considerably compared to the bare alloy
Research Interests:
Research Interests:
Publisher Summary Spiral notch torsion testing (SNTT) utilizes an extremely innovative concept of testing round-rod specimens having a V-grooved spiral notch line with a 45° angle. This chapter discusses the validity of SNTT in... more
Publisher Summary Spiral notch torsion testing (SNTT) utilizes an extremely innovative concept of testing round-rod specimens having a V-grooved spiral notch line with a 45° angle. This chapter discusses the validity of SNTT in determining the fracture toughness (KIC) as established at the Oak Ridge National Laboratory. In SNTT testing, the plane-strain condition and uniformity of stress are maintained at every point along the spiral notch line of the specimen. These unique features of SNTT also points toward another possible, though yet unexplored vista of the SNTT: the potential for evaluating KIC of the zone of lowest KIC in a specimen with microstructurally varied regions. Validation of the SNTT technique to determine KIC and KISCC (the threshold K for stress corrosion cracking, SCC) of microstructurally varied region of the same specimens will be particularly attractive for testing the specimens of weldments and determining the weakest link, such as the heat affected zone (HAZ), in industrial welds. The preliminary results of a collaborative research program of Monash University, US Naval Research Laboratory, Oak Ridge National Laboratory, and Defense Science and Technology Organization, for development and use of the novel SNTT technique for determination of threshold stress intensity for stress corrosion cracking, are also described in the chapter.
Research Interests:
Research Interests:
Some types of anodes that could replace the usual carbon anodes in aluminium production by the Hall-Heroult process are based on SnO2. The present investigation deals with SnO2-Sb2O3-CuO ceramics having an SnO2 content of ≥96%), Sb2O3 and... more
Some types of anodes that could replace the usual carbon anodes in aluminium production by the Hall-Heroult process are based on SnO2. The present investigation deals with SnO2-Sb2O3-CuO ceramics having an SnO2 content of ≥96%), Sb2O3 and CuO being dopants. The ceramic pellets, thermally treated at 1400 °C for 4 hours, were analysed by X-ray diffraction and IR spectroscopy. The structural analysis of the samples evidenced an SnO2 (ss) type solid solution. All samples were electronically conductive (small negative values of the Seebeck coefficients), having an activation energy ranging within 0.02 - 0.3 eV. The anodic polarisation curves obtained with those anodes in an electrolyte of 88% Na3AlF6, 7% Al2O3 and 5% CaF2 were studied. The results were correlated with the microstructure of the investigated samples.
Research Interests:
In the present study, combinations of a phosphonato silane with a precursor, Methyltriethoxy silane (MTEOS) in various ratios were applied onto the alloy Mg-6Zn-Ca. The corrosion resistance of the coated and uncoated specimens in a... more
In the present study, combinations of a phosphonato silane with a precursor, Methyltriethoxy silane (MTEOS) in various ratios were applied onto the alloy Mg-6Zn-Ca. The corrosion resistance of the coated and uncoated specimens in a modified simulated body fluid (m-SBF) was characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results suggest that the silane coating significantly decreases the degradation rate of the magnesium alloy, indicating its potential to be used as a corrosion barrier for magnesium alloy temporary implants.
Research Interests:
Research Interests:
Research Interests:
Résumé/Abstract The hydrogen-induced-cracking (HIC) behaviour of the magnesium alloy AZ80 was evaluated using the slow strain rate test method. The study shows no evidence of HIC in AZ80 alloy after pre-exposure or pre-charging in... more
Résumé/Abstract The hydrogen-induced-cracking (HIC) behaviour of the magnesium alloy AZ80 was evaluated using the slow strain rate test method. The study shows no evidence of HIC in AZ80 alloy after pre-exposure or pre-charging in distilled water. However, under ...
Research Interests:
Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Metallurgy, Stress corrosion cracking, and 12 moreStrain Rate, Magnesium, Zinc, Fractography, Rare Earth Element Mineralization, High performance, Grain Boundary, Rare Earth, Distilled Water, Microstructures, Stress Corrosion Cracking, and Magnesium Alloy
IntroductionCurrently, nanocrystalline materials are being widelyinvestigated due to their unique properties. This interest hasspawned the development of various techniques to synthe-size materials exhibiting grain sizes (\\20 nm)... more
IntroductionCurrently, nanocrystalline materials are being widelyinvestigated due to their unique properties. This interest hasspawned the development of various techniques to synthe-size materials exhibiting grain sizes (\\20 nm) wherephysical properties are the most exotic. Such processesinclude: high-energy ball milling [1, 2], pulsed electrode-position [3], chemical vapour condensation [4], inert gascondensation [5] etc. However, nanocrystalline samplesproduced from these techniques are either in the formof powders or thin films. Successful consolidation to arte-fact free, fully dense material is required if structuralapplications are ever to be adopted. Many methods toconsolidate these materials (i.e., hot compaction [6],explosive consolidation [7], hot isostatic pressing [8], pre-annealing–compaction–sintering [9] etc.) have been repor-ted in the literature with partial success. In general, thesuccess of these techniques for consolidation hinges on theapplication of high temperatures and pressures, which leadto explosive grain growth in nanocrystalline materials.In situ consolidation technique as developed by Youssefet al. [10] seems promising for the synthesis of consolidatednanocrystalline materials as the step of sintering to bulkdensity is no longer a need and can be eliminated. However,this technique has not been reported widely in the literatureand has been limited to nanocrystalline Zn, Al, Al alloys,copper and copper-based alloys [10, 11]. This study showsthat in situ consolidation of a FeCrNi alloy is possible usingcombination of room temperature (RT) milling and liquidnitrogen temperature milling.Nanocrystalline materials produced by high-energy ballmilling have not been well characterized and the micro-structure of these materials is not well understood. Theprimary challenge in characterization is TEM samplepreparation from ball-milled powders. Nanocrystallinepowders as produced by ball milling are too coarse to beexamined under TEM and the sample preparation for TEManalysis on such powders is not a trivial task. In general,two methods are used for the preparation of conventionalmetallic samples for TEM analysis: electro jet polishingand dimpling followed by ion milling. Nanocrystallinematerials produced by consolidation of ball-milled pow-ders can be problematic for these preparation techniques asthe consolidated samples must first be mechanically thin-ned to \\100 lm before being chemically thinned to thefinal thickness. If the material exhibits poor inter-particlebonding, the sample may not withstand the final thinning
Research Interests:
Research Interests:
Research Interests:
Corrosion-assisted propagation of an existing crack is profoundly influenced by the stress intensity at the crack tip. This article presents the first results of thermomechanical conditioning (TMC) for local manipulation of material at... more
Corrosion-assisted propagation of an existing crack is profoundly influenced by the stress intensity at the crack tip. This article presents the first results of thermomechanical conditioning (TMC) for local manipulation of material at and ahead of the crack tip, in an attempt to retard/stop crack propagation. Prenotched round tensile specimens of mild steel were subjected to rotating bending to generate a fatigue precrack, and then to apply localized thermomechanical conditioning. The threshold stress intensity factor (K ISCC ) for stress corrosion cracking (SCC) of precracked specimens with and without TMC was determined in a caustic environment. Results suggest that TMC can increase K ISCC . Finite element analysis of the specimens suggests development of compressive stresses at and around the crack tip, which is expected to improve the resistance to stress corrosion crack propagation (since stress corrosion cracks can propagate only under tensile loading).
Research Interests:
ABSTRACT The role of microbiological environments containing pure and mixed cultures of sulfate-reducing bacteria in stress corrosion cracking of carbon steel in biotic and abiotic environments was investigated. Carbon steel specimens... more
ABSTRACT The role of microbiological environments containing pure and mixed cultures of sulfate-reducing bacteria in stress corrosion cracking of carbon steel in biotic and abiotic environments was investigated. Carbon steel specimens were subjected to slow strain rate testing in a synthetic seawater environment (3.5% sodium chloride solution), with and without the microbiological cultures. Specimens tested in biotic (microbiological) conditions showed a considerable loss of ductility, as compared to those tested in abiotic conditions. Fractography of the specimens tested in abiotic solutions suggested features of only ductile failure (dimples), whereas those tested in biotic conditions had additional features of brittle cracking. Results also suggested the role of sulfate-reducing bacteria in promoting hydrogen-assisted cracking.
Research Interests:
The consequence of exposure to the dual environment of seawater sea sand concrete (SWSSC) on the inner surface and seawater (SW) on the outer surface on the durability of fibre reinforced plastic (FRP) confining tubes has received very... more
The consequence of exposure to the dual environment of seawater sea sand concrete (SWSSC) on the inner surface and seawater (SW) on the outer surface on the durability of fibre reinforced plastic (FRP) confining tubes has received very limited research attention. The durability of FRPs fabricated with different fibre types was investigated for the application of SWSSC filled tubes and SWSSC-filled double-skin tubes exposed to the external environment of SW. The colour and shininess of carbon-fibre-reinforced polymer (CFRP) surfaces generally stayed unchanged even after 6 months of exposure to the dual environment, whereas basalt-fibre-reinforced polymer (BFRP) and glass-fibre-reinforced polymer (GFRP) tubes suffered degradation. The degradation led to a ~20–30% increase in pH; however, the pH increase in the external SW was more pronounced when the internal solution was SWSSC. The extent of degradation was greater in BFRP that in GFRP. The investigation also included a specialised i...
Research Interests:
A silane-based biodegradable coating was developed and investigated to improve corrosion resistance of an Mg-6Zn-Ca magnesium alloy to delay the biodegradation of the alloy in the physiological environment. Conditions were optimized to... more
A silane-based biodegradable coating was developed and investigated to improve corrosion resistance of an Mg-6Zn-Ca magnesium alloy to delay the biodegradation of the alloy in the physiological environment. Conditions were optimized to develop a stable and uniform hydroxide layer on the alloys surface-known to facilitate silane-substrate adhesion. A composite coating of two silanes, namely, diethylphosphatoethyltriethoxysilane (DEPETES) and bis-[3-(triethoxysilyl) propyl] tetrasulfide (BTESPT), was developed, by the sol-gel route. Corrosion resistance of the coated alloy was characterized in a modified-simulated body fluid (m-SBF), using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The silane coating provided significant and durable corrosion resistance. During the course of this, hydrogen evolution and pH variation, if any, were monitored for both bare and coated alloys. The coating morphology was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) and the cross-linking in the coating was studied using Fourier transform infrared spectroscopy (FTIR). As indicated by X-ray diffraction (XRD) results, an important finding was the presence of hydrated magnesium phosphate on the sample that was subjected to immersion in m-SBF for 216h. Magnesium phosphate is reported to support osteoblast formation and tissue healing.
Research Interests:
Research Interests:
The influence of putrid seawater on the performance of mild steel has been investigated in laboratory tests with decomposing Ulva lactuca. During a 30-day period, the corrosion of steel was considerably enhanced by increased rates of... more
The influence of putrid seawater on the performance of mild steel has been investigated in laboratory tests with decomposing Ulva lactuca. During a 30-day period, the corrosion of steel was considerably enhanced by increased rates of putrefaction. However, accelerated rates of corrosion in ...
Research Interests:
Seawater and sea sand concrete (SWSSC) is a highly attractive alternative to normal concrete (NC) that requires huge amounts of fresh water and river sand. However, reinforcements of stainless steel (instead of mild steel that is used in... more
Seawater and sea sand concrete (SWSSC) is a highly attractive alternative to normal concrete (NC) that requires huge amounts of fresh water and river sand. However, reinforcements of stainless steel (instead of mild steel that is used in NC) may be required for SWSSC. This article reports investigation of stress corrosion cracking (SCC) of AISI 316 stainless steel (SS) in simulated SWSSC and NC environments, with and without addition of silica to SWSSC and NC, employing slow strain rate testing (SSRT) at 25 and 60 °C. For the purpose of comparison, SCC of SS was also investigated in simulated seawater (SW) solution. SS showed no SCC at 25 °C in any of the test solutions. Indications of SCC were seen in SW at 60 °C, but no features of SCC in SWSSC and NC at 60 °C, as suggested by scanning electron microscopy (SEM) fractographs. While the absence of SCC in SWSSC and NC is attributed to the highly passivating alkaline condition, its absence in SWSSC also indicates the role of alkalinit...
Research Interests:
Magnesium (Mg) alloys are attracting increasing interest as the most suitable metallic materials for construction of biodegradable and bio-absorbable temporary implants. However, Mg-alloys can suffer premature and catastrophic fracture... more
Magnesium (Mg) alloys are attracting increasing interest as the most suitable metallic materials for construction of biodegradable and bio-absorbable temporary implants. However, Mg-alloys can suffer premature and catastrophic fracture under the synergy of cyclic loading and corrosion (i.e., corrosion fatigue (CF)). Though Mg alloys are reported to be susceptible to CF also in the corrosive human body fluid, there are very limited studies on this topic. Furthermore, the in vitro test parameters employed in these investigations have not properly simulated the actual conditions in the human body. This article presents an overview of the findings of available studies on the CF of Mg alloys in pseudo-physiological solutions and the employed testing procedures, as well as identifying the knowledge gap.
Research Interests:
Research Interests:
Research Interests:
Chromium pre-treatments of metal have been replaced by silane pre-treatments as more environmental friendly option. Nanoparticles can be added in the silane sol-gel network have been reported to improve corrosion resistance. In this work,... more
Chromium pre-treatments of metal have been replaced by silane pre-treatments as more environmental friendly option. Nanoparticles can be added in the silane sol-gel network have been reported to improve corrosion resistance. In this work, the electrochemical corrosion resistance of low carbon steel coated with hybrid organic-inorganic sol-gel film filled with nanoparticles was evaluated. The sol-gel films have been synthesized from 3-glycidoxy-propyl-trimethoxy-silane (3-GPTMS) and tetra-ethyl-ortho-silicate (TEOS) precursors. These films have been impregnated with 300 ppm of silica or alumina nanoparticles. The electrochemical behavior of the coated steel was evaluated by means of electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Equivalent circuit modeling, used for quantifying the EIS measurements showed that sol-gel films containing silica nanoparticles improved the barrier properties of the silane coating. The silica nanoparticle-containing films showed highest initial pore resistance over the five days of immersion in 0.05M NaCl.
Research Interests:
Research Interests: Biomaterials, Electrochemistry, Calcium, Corrosion, Multidisciplinary, and 15 moreStrain Rate, Aluminum, Magnesium, Electrochemical Impedance Spectroscopy, Fracture Mechanic, In Vitro Studies, Materials Testing, Electron Probe Microanalysis, Alloys, Biocompatible Materials, Simulated Body Fluid, Body Fluids, Pitting Corrosion, Electric Impedance, and Magnesium Alloy
Research Interests:
In the present study, surface melting of a magnesium alloy, ZE41, was performed with an Nd:YAG laser, using different laser parameters (scan rate and beam type). The microstructure of the laser treated and untreated specimens were... more
In the present study, surface melting of a magnesium alloy, ZE41, was performed with an Nd:YAG laser, using different laser parameters (scan rate and beam type). The microstructure of the laser treated and untreated specimens were characterised by optical and scanning electron microscopy. The degree of microstructural refinement and melt depth was found to be a function of the laser scan rate. Electrochemical characterisation of the different laser treated specimens along with the untreated alloy was performed using electrochemical impedance spectroscopy. The laser treated specimens and untreated alloy showed similar corrosion resistance.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT For magnesium (Mg) alloys to be used as temporary biodegradable implants it is essential to establish their resistance to body fluid-assisted cracking. In this paper the fatigue behaviour of a common magnesium alloy, AZ91D, is... more
ABSTRACT For magnesium (Mg) alloys to be used as temporary biodegradable implants it is essential to establish their resistance to body fluid-assisted cracking. In this paper the fatigue behaviour of a common magnesium alloy, AZ91D, is studied in air and in modified simulated body fluid (m-SBF), and the effect of different electrochemical conditions on corrosion fatigue life is investigated. The alloy was found to be susceptible to corrosion fatigue. Results suggest inclusions and corrosion pits to be the crack initiation sites, and hydrogen embrittlement to play a dominant role in cracking of AZ91D Mg alloy in m-SBF.