Showing papers in "International Journal of Microstructure and Materials Properties in 2013"

Recent development trends in sheet metal forming

Abstract: Sheet metal forming is one of the most important key technologies in manufacturing industry. It may be reasoned by several facts, among them the economy of the sheet-forming processes concerning the material and energy consumption, as well as the overall cost efficiency. To keep this key role of sheet metal forming in manufacturing industry, a continuous development is necessary concerning the materials, the development of new innovative forming processes, the tooling and manufacturing equipment. The ever-increasing requirements stated by the automotive industry may be regarded as one of the main driving forces behind sheet-metal-forming innovations. In this paper, some recent developments in sheet metal forming will be overviewed concerning the materials and process developments, as well as the application of various methods of Computer Aided Engineering (CAE).

Multi-objective optimisation of induction heating processes: methods of the problem solution and examples based on benchmark model

Abstract: The main goal of the researches is the development of new approaches, algorithms and numerical techniques for multi–objective optimisation of design of industrial induction heating installations. A multi–objective optimisation problem is mathematically formulated in terms of the typical optimisation criteria, e.g., maximum heating accuracy and minimum energy consumption. Various mathematical methods and algorithms for multi–objective optimisation, such as Non–dominated Sorting Genetic Algorithm (NSGA–II) and optimal control alternance method, have been implemented and integrated in a user–friendly automated optimal design package. Several optimisation procedures have been tested and investigated for a problem–oriented mathematical model in a number of comparative case studies. A general comparison of the design solutions based on NSGA–II and alternance method leads to their good agreement in all investigated cases. The methodology developed is planned to be applied to more complex real–life problems of the optimal design and control of different induction heating systems.

Investigation of microstructure and element migration for rough cut surface of pure titanium after WEDM

Abstract: Wire electrical discharge machining (WEDM) process is most suitable for machining of pure titanium. Titanium is having excellent combination of properties such as high strength–to–weight ratio, low thermal conductivity and high corrosion resistance. The wire cut EDM is widely accepted for machining and shaping of pure titanium. This research work is mainly focused on experimental investigation on surface integrity of pure titanium by WEDM. The surface characteristic in terms of electrical parameters for pure titanium in WEDM process was explored. The selected machined samples were analysed using energy Dispersive X–ray analysis, scanning electron microscope (SEM) and X–ray Diffraction (XRD) techniques. It was observed that pulse on time and peak current significantly deteriorate the surface integrity of machined samples, which produce the deeper, wider overlapping craters, pockmarks, globules of debris and micro–cracks. The surface integrity of rough cut surface was based on the theory of electrical discharge phase and metallurgical physics.

Powder Injection Moulding: processing of small parts of complex shape

Abstract: Powder Injection Moulding (PIM), Metal Injection Moulding (MIM) when is limited to metals, is a fabrication route of parts with the final shape desired. This process combines the high capability of polymer injection moulding to produce complex shapes with the advantages of a powder route to process metallic, ceramic or composites materials. The process has some limitations that comes from different technological steps involved in the production of the part (feedstock production, injection, debinding and sintering). All of these different steps can be industrially controlled, being the PIM process a real alternative to produce complex parts in a high rate production method that can compete with many other processing methods to produce materials. In this work, we will go through the different steps of this manufacturing process, making special emphasis on the solutions provided by the powder technology group of the University Carlos III of Madrid (UC3M).

Creep behaviour of HDPE/wood particle composites

Abstract: The effect of particle type, size, content and manufacturing process on the creep behaviour of wood particles/High Density Polyethylene (HDPE) composites has been investigated. Short-term creep tests at different temperatures were carried out and modelled using the Burger's model and the Findley power law. The creep of the composites was found to increase with temperature due to the mobility of the amorphous bulk and tie HDPE molecules. Increased wood particle content generally decreased the creep level. Jack pine composites exhibited the highest creep reduction due to the chemical composition of the fibres surface and the efficiency of adhesion mechanism between fibres and the HDPE. Injection and compression processes led to better creep behaviour than the extrusion process due to differences in the composites microstructures. Particle size did not show important impacts on the creep properties. Findley power law led to better prediction of long time creep behaviour of the composites.

Laser Shock Processing: an emerging technique for the enhancement of surface properties and fatigue life of high-strength metal alloys

Abstract: Profiting by the increasing availability of laser sources delivering intensities above 109 W/cm2 with pulse energies in the range of several Joules and pulse widths in the range of nanoseconds, Laser Shock Processing (LSP) is being consolidated as an effective technology for the improvement of surface mechanical and corrosion resistance properties of metals and is being developed as a practical process amenable to production engineering. The main acknowledged advantage of the LSP technique includes its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly, the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. In this paper, experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (specifically steels and Aluminium (Al) and Titanium (Ti) alloys) under different LSP irradiation conditions are presented.

New frontiers for thixoforming

Abstract: The continuous increase in demand for light alloys in different applications involves manufacturing high integrity and superior performance components using cost-effective and safety processes. In this direction, the research communities together with manufacturing industries are focusing their attention to develop new products using innovative procedures, i.e., Semi-Solid Metal (SSM) processing routes. The central issue is the technological transfer to industry for affordable mass production. The purpose of this paper is to present an overview of alternative methods of production of enhanced performance light alloys components for critical areas. The origin, development and current evolution of the SSM processing are illustrated with characteristics of real-life components for automotive industry. Different techniques are presented to provide a general idea prevalently on the commercially available SSM processing techniques. A comparison with traditional methods, in particular High- and Low-Pressure Die Casting technologies, in terms of process parameters and properties is illustrated and discussed.

Effect of the squeeze pressure on the mechanical properties of the squeeze cast Al/SiCp Metal Matrix Composite

Abstract: This paper presents the results of a study carried out to understand the effect of the squeeze pressure on the mechanical properties of Al/SiCp composites, fabricated by the squeeze casting technique. Aluminium (A356) alloy reinforced with SiC particles were prepared using the stir casting route. The SiC particles are distributed in the liquid Al alloy matrix by mechanical stirring, and the melt is then subjected to different squeeze pressure during solidification. Microstructure examination of the squeeze cast composites showed the SiC particle distribution and the grain refinement in the Al alloy matrix due to the applied pressure. The hardness and density distribution also carried out to correlate with the particle distribution. The tensile and impact strength value linearly increase with the applied squeeze pressure due to the uniform distribution of particle and effect of grain refinement. At 100 MPa, the sound cast Al/SiCp composites are produced with superior hardness and tensile properties.

Microstructure and mechanical properties of Mg–Al alloys with in situ Al4C3 phase synthesised by CO2 incorporation during liquid state processing

Abstract: In this work, Mg–Al alloys containing 7 wt.% and 9 wt.% Al were synthesised by the incorporation of carbon dioxide during casting, using the disintegrated melt deposition technique and were characterised after extrusion. Microstructural studies revealed fine–grained structure and phase analyses of Mg–7Al–CO2 and Mg–9Al–CO2 showed the presence of Al4C3 phase formed in situ during processing. Evaluation of mechanical properties of these alloys phase showed improvements in hardness, yield strength and ultimate tensile strength when compared to those without the incorporation of CO2. The observed enhancement in mechanical properties was attributed to the dispersion strengthening effect brought forth by the in situ Al4C3 phase. Based on the processing–structure–property correlation, the significant influence of CO2 incorporation and the processing methods on the microstructural and mechanical properties of the alloys are discussed.

Characterisation of oxidation and wear oxidised surfaces of H13 steel/brass in dry sliding conditions

Abstract: Although oxide scale has significant influence on surface quality of hot–worked products, deformation of the scale during hot working has not been understood sufficiently. The authors propose an experimental study to analyse the oxidation and the tribological behaviour of a ferrous alloy (X40CrMoV5–1, H13 steel) and non ferrous alloy (CuZn39Pb3, brass alloys) in dry sliding conditions. The tribological behaviour of the pair of materials is carried out on a pin–on disk wear tester after oxidation at 600°C for 70 h. It was found that: i) a loose oxide film wholly covered the surface of the steel; ii) Fe2O3 as the main oxide was identified except for a small amount of Fe3O4; iii) during friction, a compacted oxide film was established on the worn surface of the steel. The analysis of the worn surface showed two regions: a delamination region due to the delamination of tribo–oxide during wear and an undelamination region characterised by the dominance of Fe3O4 tribo–oxides on the worn surface.

Mathematical modelling and computer simulation of mechanical properties of quenched and tempered steel

Abstract: A mathematical model and method of computer simulation for the prediction of mechanical properties of quenched and tempered steel were developed Numerical modelling of hardness distribution in as-quenched steel components was performed based on experimental results of Jominy test Modified Jominy test was designed for hardenability prediction of high-hardenability steels Hardness of quenched and tempered steel was expressed as a function of maximal hardness of actual steel and representatives of chemical diffusivity of steel according to the time and temperature of tempering Yield strength and fracture toughness distributions were estimated using the Hahn−Rosenfield approach Fatigue resistance was estimated based on predicted microstructure and hardness Distribution of other relevant mechanical properties was found out based on predicted as-quenched and tempered hardness of steel Experimental investigation was performed on high-hardenability steel for tools and dies The established procedure was applied in computer simulation of mechanical properties of a quenched and tempered steel workpiece

Effect of laser surface alloying on structure of a commercial tool steel

Abstract: This research project presents the investigation results of laser remelting and alloying especially the laser parameters and its influence on the structure and properties of the surface of the 32CrMoV12-28 hot work steel, using the High Power Diode Laser (HPDL) As a result of the performed research structure changes were determined concerning the grain size and reinforcement ceramic particle distribution in the steel surface layer The reason of this work was to determine the optimal laser treatment parameters, particularly the laser power applied to achieve good layer mechanical properties for protection of this hot work tool steel from losing their work stability and to make the tool surface more resistant to action in hard working conditions The remelted layers which were formed in the surface of investigated hot work steel were examined metallographically and analysed using light and scanning electron microscope as well as X-Ray diffraction

Dry sliding wear behaviour of Friction Stir Welded aluminum (6061)-B4C composite

Abstract: Different weight percentage of B4C particulates reinforced Aluminum Matrix Composites (AMCs) are fabricated by modified stir casting route. The produced AMCs are Friction Stir Welded (FSW) using a four factor five level central composite design matrix. The dry sliding wear properties of nugget zone of the FSW composites were analysed using a pin-on-disc wear testing machine. The presence of B4C particulates and fine grain in the weld nugget improved the wear properties. The relationships between the wear rate of AMCs and friction stir welding process parameters were established using a regression model. The developed regression model was optimised to minimise the wear rate using the Generalised Reduced Gradient (GRG) method. The worn out surface characteristics of welded composites were studied using scanning electron microscopy. The numerous pits, grooves and wear tracks were observed in the microstructure.

Investigation of microstructure and material properties for 18 different graphitic cast iron model materials with focus on Compacted Graphite Iron (CGI)

Abstract: The higher mechanical strength of Compacted Graphite Iron (CGI) than Flake Graphite Iron (FGI) makes it very useful material for several commercial components. The knowledge of microstructure and hence the mechanical properties and machinability is very important for the CGI to used efficiently in manufacturing. The complex geometry of cast components makes it difficult to produce adequate microstructure in the whole component.Adequate material properties can be achieved by having good knowledge about the correlations between the casted geometry, graphite morphology and pearlite content. In the presented paper, 18 different model materials have been analysed extensively, concerning the effect of chemical composition, solidification and cooling rate on the nodularity, pearlite content, interlamellar spacing in pearlite, hardness and mechanical properties. Later, the cutting force measurement tests were performed on some of the materials and it was found that the forces have a strong positive correlation with pearlite content and the tensile strength of the materials.

Multilayer laser-assisted deposition on single crystal superalloy substrates

Abstract: Laser powder deposition is a promising method for repairing single crystal Ni-based superalloy components used in the hot section of gas turbine engines. In this paper, recent results on multilayer deposits of NiCrAlY and Rene N4 on (100) single crystal substrates of SRR99- and CMSX-4 Ni-based superalloys are summarised. The deposited material presents a columnar dendritic microstructure consisting of arrays of similarly oriented dendrites forming a mosaic single crystal. Since solidification is epitaxial, the deposits inherit the orientation of the substrate. After aging, the �� '-Ni3Al precipitates do not present the cuboid shape required for high-temperature strength owing to chemical segregation within the dendrite arms resulting from solidification solute partition. Heat treatments capable of creating the proper particle microstructures were devised.

Influence of laser deposition technique on surface integrity of 12 Ni maraging tool steel

Abstract: The aim of this investigation is to study the material properties of two coating deposition techniques on 12 Ni maraging tool steel specimens. The first technique is the Nd:YAG laser cladding with coaxial powder injection and the second is the hybrid process of flame spraying with subsequent Nd:YAG laser remelting of sprayed coating. The subsequent precipitation annealing is necessary to obtain the material with similar properties as base material. The surface integrity was studied based on macro- and microstructural examination, chemical analysis and the microhardness and the residual stress distribution. All specimens were precipitation-hardened on required hardness. The through-depth residual stresses were measured and compared. The research shows that the material quality of laser-cladded layers is better than that of layers that were sprayed and laser remelted.

Tribological failure analysis of ball valve seals

Abstract: The ball valve seals are exposed during their use to thermal gradients (alternating the flow of cold and hot water), static loading (clamping force) and cyclic loading (alternating opening and closing) which can be sources of valve failures. The ball valves usually fail as a result of different failure modes such as wear, plastic deformation and corrosion. In order to describe these modes a failed ball valve which was belonged to a sanitary installation is investigated. The investigation of the failure was carried out by using several experimental tests including optical microscopy and Scanning Electron Microscopy (SEM). Tests were performed on a specific reciprocating tribometer for ball valve seals application. Experimental results revealed that the friction behaviour of polymeric seal depends strongly on the clamping load of seal and the manipulation frequency of counterface ball. Optical microscope observation of the worn surface showed that strong adhesion of the polymeric transfer layer to the counterface ball.

The effects of special extrusion on the grain refinements of magnesium alloy

Abstract: To research the effects of extrusion process and its process parameters on evolutions of microstructures for magnesium alloy, and the process includes initial extrusion and subsequent shearing process and is shorten for 'ES'. The simulation models have been built by using the DEFORM software. Temperature and strain evolution for deformation varying with initial billet temperatures has been explored. An experimental extrusion with installed container and ES die has been constructed. The maximum temperature rises in the billets are not increasing with billet temperature rise. The temperatures of rod surface increase continuously with development of ES extrusion. ES processes can improve microstructure refinement of AZ31 magnesium alloy. The simulation results and microstructure observation show that ES process can introduce compressive and accumulated shear strains into the magnesium alloy and improve the dynamic recrystallisation during ES extrusion. The research results show that ES is an efficient and inexpensive grain refinement method for magnesium alloys.

An investigation on the effect of porosity on the transport properties of porous silicon

Abstract: Microelectronics technology today is dominated exclusively by Silicon (Si). The inefficiency of Si to emit light even at cryogenic temperatures has been overcome with the discovery of porous silicon (PS) and its visible luminescence at room temperature. The present investigation aims at analysing the effect of increasing porosity on the transport properties of porous silicon with reference to field and temperature–dependent dark and photo conductivity and further substantiating the results with modulation techniques. Pure silicon wafer of n–type was made porous by immersion in an appropriate etchant for a few minutes. The conductivity was found to increase as porosity increased and this effect could be attributed to the increase in the trap levels, with increasing porosity. Temperature–dependent studies reveal a decrease in activation energy with increase in porosity indicating an increase in conductivity. Reflectance and electroreflectance measurements were used to calculate the band gap of porous silicon. It was found to lie closer to the direct band gap of silicon. A reduction in the band gap of porous silicon has been observed.

Stress redistributions in unit cells of fibre-reinforced polymer composites with interface degradation

Abstract: Fil: Godoy, Luis Augusto. Universidad Nacional de Cordoba. Facultad de Ciencias Exactas Fisicas y Naturales. Departamento de Estructuras; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Effect of particles size on the magnetocaloric properties in Gd5Si2Ge2

Abstract: In this study, the effect of particle size on the magneto-thermal properties of Gd 5 Si 2 Ge 2 alloys was investigated. It is found that the alloy powders obtained via the milled processing conditions possess distinctly Magnetocaloric Effects (MCEs). The magnetic entropy change (∆SM) of the milled Gd5Si2Ge2 alloy powders for the 38.5-50 um arrives the maximum value of -∆SM = 9.06 J·kg −1 ·K −1 for magnetic field change under 2.0 Tesla. The estimated Relative Cooling Power (RCP) for the 50-74 um powders is around 155.94 J kg −1 , which increases 28% comparing with that of the as-cast alloy (121.67 J kg −1 ). These results indicate that the particle size in the micrometre range can remarkably affect the MCE in the alloys, and consequently, strong influence on the conversion performance. Therefore, care should be taken to choose the appropriate particle size for the magnetic refrigerant materials.

Residual stress, fatigue and electrical conductivity analysis after shot peening of aluminium alloy AlZn5.5MgCu

Abstract: The paper deals with the effect of different shot peening (SP) treatment conditions on the aluminium alloy AlZn5.5MgCu. The objective of the research was to establish the optimal parameters of the shot peening treatment of the aluminium alloy in different precipitation hardened states. The resulting residual stress profiles reveal that stresses throughout the thin surface layer of all shot peened specimens are of compressive nature. Comparison of different temperature of precipitation hardening of aluminium alloy shows that changes after different shot peening conditions have greater effect than coverage. Wohler curves were determined in the areas of maximum bending loads between 30–65% of material's tensile strength. The results of material fatigue testing differ from the level of shot peening on the surface layer. Also electrical conductivity measurements were performed by means of eddy currents with the objective of distinguishing the effects of precipitation hardening and microplastic deformation on individual specimens.

ZnO nanostructures on different silicon–based substrate via simple sol–gel immersion method

Abstract: In this work, ZnO nanostructures using zinc nitrate as starting material grown on different silicon–based substrate were studied. Porous silicon was prepared by electrochemical etching to modify the silicon surface. Field emission scanning electron microscopy (FESEM) displays different distribution and nanostructures of ZnO on different substrate. The seeded substrates show the better site for the growth of ZnO nanostructure due to presence of nucleation site. Crystalline of ZnO nanostructure were investigated by X–ray diffraction (XRD) grating. It is found that the hexagonal wurtzite of ZnO nanostructures were produced for all samples. The peaks (100), (002) and (101) are dominating for all samples prove that hexagonal structures of ZnO were formed. Photoluminescence spectra were employed in order to study the optical properties. The peak centred at 395-398 nm corresponds to free–exciton recombination ZnO nanostructures are found in silicon and porous silicon, respectively.

Dislocation configuration evolution of FCC alloys induced by Laser Shock Processing

Abstract: To investigate the relations between dislocation motion and microstructure evolution of FCC metals during Laser Shock Processing (LSP), and then improve the understanding of the mechanism of laser shock strengthening, aluminium alloy 2A02 and austenitic stainless steel 201 were selected as the representatives, and laser shocked by the Nd:YAG laser with 1064 nm output wavelength and 20 ns short pulse. The microstructure evolution of test materials induced by laser shock was analysed via Transmission Electronic Microscope (TEM) and Inverse Fast Fourier Transformation (IFFT), and the dislocation configurations and their function were discussed. The experimental results indicated that the increase in both the surface hardness and the residual compressive stress of the laser-shocked test materials can be attributed to the contribution of complex dislocation configurations and nano-crystallisation.

Effect of extrusion on the microstructure and properties of 2014–based particulate composites

Abstract: An attempt has been made in this paper to improve upon the properties attained in cast 2014–based metal matrix composites (MMCs) made with SiC dispersoids through extrusion under optimised conditions. The properties attained have been compared between the cast and extruded MMCs in terms of microstructure, physical, mechanical and sliding wear properties, and improvements attained. Attempts have been made to analyse the obtained results through microscopic investigations on the tested samples.

Influence of welding conditions on resistance flash welds

Abstract: The contribution gives an insight into resistance flash welding with emphasis on process dynamics. For the experiments ribbed mild steel concrete reinforcement bars were used with a range of welding parameters used in a normal welding praxis. The welded bars were tested for tensile strength and the results were used to develop a regression model. The model was designed to predict weld piece strength according to input welding parameters. The input welding parameters were: welding force, welding current and welding time.

Phase transformation in Al-Cu-Fe Alloys produced by induction fusion

Abstract: Structural characteristics and thermal behaviour of the conventionally solidified Al–Cu–Fe alloys prepared by magnetic induction melting with nominal compositions of Al80Cu14Fe6, Al65Cu23Fe12 and Al72Cu13Fe15 were investigated by scanning electron microscopy, X–ray diffraction, optical micrographs and differential thermal analysis. The icosahedral quasicrystalline (i–QC) phase is obtained in Al80Cu14Fe6 alloy only after heat treatment at 500°C contrarily to Al65Cu23Fe12 and Al72Cu13Fe15 and coexists with other crystalline intermetallic phases: cubic β–Al(Cu,Fe), monoclinic λ–Al13Fe4 and tetragonal θ–Al2Cu. Vickers Microhardness variation with alloy composition as–solidified and heat treated has been also used in this work to determine the intrinsic mechanical hardening of the Al–Cu–Fe alloys.

Comparative studies on GTA and PCGTA weldments of AISI 4140 and AISI 316 dissimilar metals

Abstract: In this study, an attempt has been made to investigate the weldability, mechanical properties of dissimilar weldments of AISI 4140 and AISI 316. These dissimilar metals were welded using gas tungsten arc welding (GTAW) and Pulsed Current GTAW (PCGTAW) employing ER309L filler wire. It was observed from the tensile test results that the fracture was occurred at the parent metal of AISI 316 in all the trials for both the weldments. On examining the SEM fractographs, the mode of fracture was found to be ductile in nature. In addition, the scanning electron microscopy and electron dispersive X–ray spectroscopy (SEM/EDS) analysis was performed at various zones of the as–welded samples of AISI 4140 and AISI 316 to reveal the structure–property relationships.