Metallurgical Microscope Research Articles

Influence of TiO2 dopant on spontaneous infiltration to fabricate high volume fraction SiCp/Al cermets

The influence of particulate TiO2 dopant on the rate of spontaneous infiltration into SiC preforms by molten Al alloys and the characteristics of the prepared SiC–Al cermet were investigated qualitatively. To examine the effectiveness of the TiO2 dopant as an infiltration aid, spontaneous infiltration experiments were carried out at different temperatures for preforms doped with TiO2 and for preforms without dopant. Results showed that TiO2 enhances the spontaneous infiltration rate at each temperature level. Via metallurgical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and differential scanning calorimetry (DSC), the characteristics of the cermets produced at different process parameters were examined. The relevant reaction processes between TiO2 and Al and the experimental results are discussed.

Comparative investigation of the fatigue limit of additive-manufactured and rolled 316 steel based on self-heating approach

In this paper, fatigue properties of additive-manufactured (AM) 316 steel are investigated by the rapid fatigue limit evaluation method based on self-heating experiments. To this end, a series of tensile cycling experiments are carried out on AM 316 steel specimens; temperature variation resulting from the self-heating phenomenon is recorded by an infrared thermography (IR) camera and fatigue limit is deduced. To compare with the properties of traditionally processed materials, the fatigue limit of rolled 316 steel is also investigated using the same procedure. The experimental results show that the AM 316 steel has a higher fatigue limit than rolled one. In order to interpret this result, microstructures of AM and rolled 316 steel are characterized by metallurgical microscope and X-ray diffractometer (XRD). Furthermore, a crystal-plasticity-fatigue-based model is developed and cyclic simulations are carried out. The difference of fatigue limit between AM and rolled 316 steel is discussed experimentally and numerically from microscopic viewpoint, including grain size and dislocation density. It is shown that: (1) the AM process induces coarsening of the grains and reduction of ductility, and (2) ductility plays a much important role than refining grain size on fatigue limit. For this reason, AM 316 steel presents a higher fatigue limit than 316 rolled steel.

Effect of preheating temperatures on distribution of FeTiO3 on A 360 aluminium alloy by stirring

An investigation on distribution of 5 wt% of natural mineral called ilmenite (FeTiO3) an extract from iron ore particles in A 360 aluminium metal matrix composite (MMC) by manual stirring. In preparing the MMC, the FeTiO3 was preheated at different temperatures, namely at 200 °C, 400 °C, 600 °C, and 800 °C and then added to the MMC in an equal interval of time and the 5 wt% of FeTiO3 was evenly distributed. Microstructure of the MMC was observed using a metallurgical microscope. The deposition of FeTiO3 on eutectic Si was revealed during the microscopic observation. Composition of the cast MMC was analyzed using EDS. The result of the EDS analysis confirmed the presence of FeTiO3 content on the MMC compared to the substrate. Further the compositions of intermetallic phases were obtained during the EDS analysis. The XRD spectrum confirms the presence of intermetallic phases. The hardness and tensile strength of the MMC reinforced with FeTiO3 preheated at various temperatures was found to be increased when compared to the MMC.

Effect on distribution of siderite on aluminium – 7% silicon alloy by stir casting

An investigation on distribution of Siderite (FeCO3) at the incremental at 1 Wt.% to Aluminium Matrix Composite (AMC) by stir casting. In preparing the Metal Matrix Composite (MMC), the FeCO3 was pre-heated at a temperatures of 200 °C and then added to the AMC. Microstructure of the MMC was observed using a metallurgical microscope. The distribution of FeCO3 on eutectic Si was revealed during the SEM imaging. Composition were analyzed using EDS. The result of the EDS analysis confirmed the presence of FeCO3 content on the MMC compared to the substrate. The elemental mapping shows the formation of intermetallic phase on the MMC. Further the compositions of intermetallic phases were obtained during the EDS analysis. The XRD spectrum confirms the presence of intermediate phases. The hardness and tensile strength of the MMC reinforced with FeCO3 at various wt% was found to be increased when compared to the MMC.

Effect of Ni doping on the microstructure and magnetic properties of Fe–Ga ribbons

A set of Ni doping Fe–Ga ribbons were fabricated using melt spinning method. The microstructure was studied using extended X-ray absorption fine structure spectroscopy (EXAFS), high resolution X-ray diffraction (HRXRD) and metallurgical microscope. The results of microstructure indicated that as Ni concentration increased, the lattice matrix transformed from body-centred cubic (bcc) to face-centred cubic (fcc), with the decrease of unit cell volume and the emergence of little amount B2 and E21 phase. The result of magnetic and magnetostrictive properties showed that the saturation magnetization decreased with Ni doping. (110) texture in studied ribbons resulted in low saturation magnetic field and high saturation magnetostrction. In addition, small amount of precipitated phase E21 improved the magnetostricion of FeNiGa ribbons.

Wear behaviour of cast aluminium silicon (Al-Si) alloy in Dot 4 brake fluid

The frictional sliding behaviour of cast Al-Si alloy was investigated with and without DOT 4 hydraulic brake fluid lubrication/environments. Cast Al-Si specimen was produced from wrought alloy and the specimen surface was metallurgically prepared. The as-cast product was characterized with aid of micro-hardness tester, the chemical composition was analysed by X-ray fluorescence (XRF), while X-ray diffraction (XRD) was used to identify phases present, microstructures and surface examinations were done on a high resolution metallurgical Optical Microscope. The properties of the polished and worn sample surfaces were examined by Scanning electron microscope (SEM) equipped with Energy dispersive X-ray (EDS) facilities. A 6mm diameter alumina ball under varying normal loads (3-10 N) was rubbed against the surface of the cast Al-Si coupon specimen. The dry and wet sliding wear behaviour was assessed based on the CoF-sliding time behaviour. From the results, the average CoF values of 0.9064 for dry and 0.2038 for wet contacts were obtained. Comparatively, 1.03E-06 and 4.21E-07 minimum wear intensities; and 467290 and 132170 wear resistances were obtained for dry and wet contacts respectively. Behaviour of cast Al-Si in DOT4 were compared with its performance in DOT3 regarding the hydraulic brake system application.

Characterisation and wear behaviour of rolled carbon steel in Dot 4 brake fluid

The wear behaviour of as-rolled carbon steel (ARCS) in DOT4 brake fluid is investigated and reported in this study. Sample was characterised using chemical analysis, hardness, impact and tensile strength tests. Arc-spectrometry and the Energy Dispersive X-Ray (EDS) facilities were used to ascertain the chemical compositions. The microstructures and wear track patterns of samples were evaluated using Scanning Electron Microscopy (SEM) and High-resolution metallurgical microscope. The wear of as-rolled carbon steel (ARCS) samples subjected to reciprocating motion of loads at room temperature and constant wear time were compared in air, DOT4 fluid and water. The frictional behaviour and wear track patterns of the specimens subjected to varied normal loads (3, 5 and 10N) under reciprocating sliding wear were employed to assess the wear damage of samples in the three different environments. The coefficient of friction (CoF) obtained tends to be in the order of μDOT4 brake fluid < μwater < μair comparatively for the three test environments.

Effect of heat treatment on wear behaviour of rolled carbon steel in DOT4 brake fluid

The wear of heat-treated rolled carbon steels (HTRCSs) were performed under dry and wet sliding in DOT4 brake fluid is successfully investigated and reported in the study. The HTRCSs samples were obtained by heating to and soaking the as-rolled carbon steel (ARCS) at 950 °C prior to quenching or cooling in different media at different selected temperatures between (20 and 250 °C) and atmospheric conditions. The microstructures and wear track patterns of specimens were evaluated using SEM and high-resolution metallurgical microscope. The sliding wear behaviour and wear track patterns of the specimens impressed under 10N normal loads and reciprocating mode was used to assess the wear damages. The obtained wear properties were compared in air and DOT4 fluid environments using Anton Paar TRB tribometer. The results obtained showed that enhanced wear behaviours were obtained from the oil and water quenched samples as compared with the air and furnace cooled samples. The HTRCSs samples are more tolerable than as-rolled sample (ARCS) under dry sliding. However, beside the influences of the heat treatments, the lubricating effect of DOT4 is more pronounced in the results. The CoF ranges from 0.105 to 0.137 for wet sliding while higher CoF values (0.378-0.934) were obtained in the dry sliding.

Determination on the Effect of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/B&lt;sub&gt;4&lt;/sub&gt;C on the Mechanical Behaviour of Al-6.6Si-0.5Mg Alloy Cast in Permanent Mould

The present research includes the analysis of mechanical properties of A356/ hybrid metal matrix composite. The mechanical behaviour - hardness, ductility, tensile and yield strength were studied. Reinforcement of these composite specimens were with a weight percentage of (wt - %) 10%, 20% and 30%. The microstructure of these specimens at different wt - % of reinforcements were viewed under an optical metallurgical microscope. It was observed that at 30 wt - % of reinforcement addition, there was a finer distribution of reinforcement particles and as the wt - % decreased, much leaner distribution was observed. The hardness test was carried out using a Vickers Hardness Tester. From the experiment it was noted that with an increase in the amount wt - % of reinforcement, there is a subsequent increment in the mechanical properties except in the case of percentage elongation, which was observed to decrease with an increase in the reinforcement content.

Effect of lanthanum, cerium and other elements on the electrochemical corrosion properties of Pb–Ca–Sn–Al alloy in lead–acid batteries

The effects of different additives including selenium, silver, ytterbium, lanthanum, and samarium with a dosage of 0.02 wt.% ± 0.005 wt.% on the electrochemical behavior of Pb–Ca–Sn–Al alloy have been studied in sulfuric acid solutions. The electrochemical properties were evaluated by linear potential sweep (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Metallurgical microscope and scanning electron microscope (SEM) were employed to investigate the morphology-property relationships of the corrosion layer and corrosion section of Pb–Ca–Sn–Al alloys. It was found that the additives including Ag, La and Sm can to some extent refine the grain and regular grain boundary of Pb–Ca–Sn–Al alloy, which was confirmed by metallurgical microscope. The formation of a uniform and dense corrosion layer on the surface of these three alloys can effectively reduce the corrosion rate of the alloy. Furthermore, the growth of Pb (II) and PbO2 in corrosion layer on Pb–Ca–Sn–Al alloy is remarkably inhibited by adding Ag, La, and Sm as determined by the results of CV, EIS, and SEM. These experimental facts indicate that adding Ag, La and Sm can improve the corrosion resistance of the alloy.

Study of bainitic transformation kinetics in SAE 52100 steel

The objective of this research was to investigate the bainitic formation in austempered SAE 52100 steel. The original microstructure of SAE 52100 steel consisted of spheroidized pearlite. In the formation of bainite, SAE 52100 steel samples were austenitized at a temperature of 849 °C for 20 min, and then quickly quenched to the isothermal temperatures between 232 °C and 427 °C for various holding times from 20 s to 120 min. The hardness and microstructure of austempered SAE 52100 samples were analyzed using a Rockwell C hardness tester and metallurgical optical microscope. In addition, the bainitic formation in SAE 52100 steel was characterized using the theory of kinetic phase transformation. The activation energies of lower bainite and upper bainite microstructure were found to be 4.72 × 104 J/mol and 6.07 × 104 J/mol with frequency factors of 23.03 (1/s) and 273.65 (1/s), respectively.

Effect of Silicon Inclusion Carbonaceous Composite Particulate on the Thermal-Ageing Characteristics and Mechanical Performance of Low Carbon Steel

This study focus on the effects of silicon inclusion carbonaceous particulate on the hardness and microstructural properties of carburized low carbon steel, at constant temperature of 900 °C with different holding time from 2 to 5 h. The cow bone and coal dust composite particles were varied with 20% CaCO3 used as the energizer. Hardness and microstructural testing of the various specimens were then carried out using Vickers hardness machine and metallurgical scanning electron microscope. From the result, it was noticed that there was an increase in microhardness performance on both cow bone and coal dust reinforced matrix compared to the as-received samples. For coal dust carburized carbon steel, the hardness value improved from 286 HVN control samples 434.55 HVN in 5 h. It was seen that the introduction of cow bone composite particulate also provides a reasonable mechanical hardness improvement to 418.2 HVN although a little short fall against the coal dust metal matrix. From the microstructure and macrostructure studies highly pearlitic matrix steel was observed with grain refinement of CB and CD found at the interface providing an effective nucleation site along the boundaries.

Fabrication of Porous Gold Film Using Graphene Oxide as a Sacrificial Layer.

An original and simple fabrication process to produce thin porous metal films on selected substrates is reported. The fabrication process includes the deposition of a thin layer of gold on a substrate, spin coating of a graphene oxide dispersion, etching the gold film through the graphene oxide layer, and removing the graphene oxide layer. The porosity of the thin gold film is controlled by varying the etching time, the thickness of the gold film, and the concentration of the graphene oxide dispersion. Images by scanning electron and metallurgical microscopes show a continuous gold film with random porosity formed on the substrate with a porosity size ranging between hundreds of nanometers to tens of micrometers. This general approach enables the fabrication of porous metal films using conventional microfabrication techniques. The proposed process is implemented to fabricate electrodes with patterned porosity that are used in a microfluidic system to manipulate living cells under dielectrophoresis. Porous electrodes are found to enhance the magnitude and spatial distribution of the dielectrophoretic force.

THE EFFECT OF CURRENT VARIATION ON MICRO STRUCTURE AND HARDNESS IN ALLOYSTEEL SS400 WELDING PROCESS USING SMAW METHOD

This research aims to find out the effect of current on microstructure and hardness value in Alloy Steel SS400 before (raw material) and after welding using Shielded Metal Arc Welding (SMAW). This research uses experiment methods. Technique of analyzing data used was a descriptive comparative research. The instruments used for testing microstructure and hardness were Olympus Metallurgical Microscope and Vikers Hardness Tester. Base on the result of research, it could be concluded that the result of microstructure testing showed the improved ferrite structure after welding. In raw material, ferrite structure seemed to looks evenly, but the result of welding using SMAW welding method with current of I20 A, 130 A, and 140A showed that ferrite structure reduced in each specimen, so that perlite structure was very dominant. The hardness value of hardness result showed the different hardness level. The specimen with current of 140 A had higher hardness level of 231,055 VHN than the specimen with current of 120 A (219.222 VHN) and 130 A (223,333 VHN). The result of hardness testing on raw material was 182,333 VHN. This research showed that the welding using varying current changed microstructure and affected the hardness value of Alloy Steel SS400.

THE EFFECT OF QUENCHING MEDIA VARIATIONS ON MICRO STRUCTURE AND VIOLENCE OF THE S45C STEEL STEEL WELDING RESULTS

The purpose of this research is to find out the effect of current on microstructure and hardness value in S45C steel before (raw material) and after welding using Shielded Metal Arc Welding (SMAW). This research using experiment method. The Technique of data analysis using descriptive comparative research. The instruments that used for testing microstructure and hardness is Olympus Metallurgical Microscope and Vickers Hardness Tester. Based on the results of the research conclude that (1) the results of the microstructure testing showed the improved martensite structure after welding. In the raw material, martensite structure didn’t exist but the result of SMAW welding methods using quenching media of water, oil, and air that showed martensite structure was exist. (2) The hardness value of raw material is 232 VHN. The specimen with water media had highest average hardness value that is 411 VHN, oil media had average hardness value that is 308 VHN, air media had lowest average hardness value that is 263 VHN. This research showed that the result of SMAW welding using varying quenching media can changed the microstructure and hardness of S45C steel.

Fabrication of 6061Al–5 wt%TiB2 In Situ Composite Strips by Mixed Salt Method and Twin-Roll Casting

6061Al–5 wt%TiB2 in situ composite strips were produced by a novel process. For comparison, the as-cast composites were prepared by the commonly used method and processed into strips. In the process, 6061Al–5 wt%TiB2 slurry was prepared by using the mixed salt method by making the molten Al react with stoichiometric mixed salts of KBF4 and K2TiF6. To fabricate the composite strips of as-cast state and cast-rolling state, the slurry of 50-min insulation was cast into a permanent mould and a twin-roll caster, respectively. Microstructures of both as-cast state and cast-rolling state were investigated by metallurgical microscope, X-ray diffraction, scanning electron microscope, and transmission electron microscope, and ultimate tensile tests were conducted to evaluate the mechanical properties thereof. The experimental results demonstrated that the twin-roll casting could significantly improve the microstructure and mechanical properties of the aluminium matrix composite strips. The microstructural improvement for the cast-rolling state was due to the quick cooling and deformation along the cast-rolling direction. The yield stress, the ultimate tensile strength, and the elongation of the cast-rolling state got improved by 67.9%, 31.9%, and 19.24%, respectively, compared with the as-cast state.

EXPERIMENTAL INVESTIGATION ON TAPPING OF Al6061/SiC METAL MATRIX COMPOSITE WITH 2 AND 4 MICRONS TiAlN COATED STRAIGHT FLUTED HSS MACHINE TAPS

The objective of this work is to evaluate the performance of straight fluted HSS machine taps with 2 microns and 4 microns thickness of TiAlN coating on tapping of Al6061/SiC metal matrix composite. The methodology includes the fabrication of Al6061/SiC Metal matrix composite by stir casting process with 5, 7.5 and 10 weight percent SiC particles. Tapping operation was performed under dry conditions with different cutting speed and constant feed rate equal to the pitch of the thread. The specimens were drilled and tapped with HSS M8X1.25 machine taps coated with TiAlN coating of 2 and 4 micron thickness, in a CNC vertical machining center. The performance of HSS machine taps was evaluated in terms of tapping torque, tool flank wear, and quality of threads produced. Torque and thrust were measured using a drill tool dynamometer of Kistler make. Quality of threaded holes was analyzed by capturing the thread profile using a metallurgical microscope. The estimation of progressive flank wear of HSS machine taps was done using the profile projector. Increase in weight percentage of SiC particles and tapping speed would increase the torque required for tapping, rate of flank wear of the tool and decrease the quality of threaded holes. The progressive flank wear was found higher in machine taps with 2 microns thickness of TiAlN coating when compared to taps with 4 microns thickness of TiAlN coating. Influence of cutting speed on progressive flank wear of HSS machine tap was found to be higher compared to the thickness of TiAlN coating on the tap and weight percentage of SiC.

Strengthening mechanism and properties of Co–WC composite coatings deposited by plasma‐transferred arc welding

Cobalt (Co)-based tungsten carbide (WC) wear-resistant coatings with different content of WC were prepared on the surface of Q235 low carbon steel by plasma-transferred arc welding. The properties of the coatings such as strengthening mechanism, microhardness and wear properties were tested by using a metallurgical microscope, scanning electron microscope, energy dispersive spectrometer, X-ray diffraction, Rockwell hardness tester, and friction wear equipment. The results show that the main reasons for the strengthening of spray welding layer are the solution strengthening formed by α-Co with supersaturated tungsten (W) and the dispersion strengthening caused by eutectic precipitated carbide and silicide. The proportion of the solid solution of W in α-Co steadily ranges from 18.00 to 19.59%. The morphologies of rich W-phase are mainly related to the content of W. With the content of W increasing, the evolution process of the shape is the amorphous form→damascene shape→star-like shape→the polygon. Amorphous W-rich phase can be obtained when the content of WC ranges from 20 to 30%, evenly distributed W-rich phase in the shape of damascene or star can be obtained when the WC content ranges from 30 to 40%, and the polygonal W-rich phase can be obtained at the percentage of 40-50%.

Variation of the key morphological, structural, optical and electrical properties of SILAR CdO with alkaline earth Ca2+ ions doping

Abstract Pristine and alkaline earth Ca2+ ions doped (CaxCd1-xO (0 ≤ x ≤ 0.025)) CdO films were fabricated by SILAR technique on the soda lime glass substrates. The influence of increasing Ca content on the morphological, structural, optical and electrical properties of deposited films was analyzed. Metallurgical Microscope (MM), Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) images of the samples exhibited that the morphology was dramatically changed with the addition of Ca to the synthesis solution when compared to the pristine CdO film. Energy Dispersive Spectrometry (EDS) analyses confirmed the presence of Ca in the doped films. X-ray diffraction (XRD) analysis of the pristine and Ca-doped CdO films exhibited cubic crystalline structure with preferred orientation of (111) and (200) direction. The existence of chemical bonding was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) study. Optical studies revealed that the energy band gap were dependent on Ca-doping content in accordance with both Vegard's relation and Tauc's law calculations. The impedance analysis and four-point probe measurement results of CdO thin films were studied. Sheet resistances of the thin films were increased by Ca doping up to doping level of 1.5%. Further doping level causes degradation in sheet resistance.

Impact of tungsten on microstructure, hardness and wear rate of AISI 304 stainless steel surface alloyed under nitrogen environment

An examination was carried out on AISI304 Stainless steel with tungsten by surface modification using Gas Tungsten Arc as a heat source at a constant flow of nitrogen gas added to Argon shielding atmosphere. The microstructure of the W - modified area were observed using a metallurgical microscope. The composition of the surface modified layers were analyzed using EDS. The result of the EDS analysis confirmed the presence of W and N2 content in the modified layers. Further, the presence of intermetallic phases were found during the XRD analysis. Hardness measurements were carried out along the depth direction. The hardness increased by 2010HV on the W- modified layer under N2 atmosphere compared to the 277HV of the substrate. It is noticed that the wear resistance in the surface modified area improved to 0.8 × 10−4 mm3 / N-m from 10.94 × 10−4 mm3 / N-m of the substrate. The reduction in grain size, formation of intermetallic phases, and dispersion of W – particle in the modified layers has improved the hardness and the wear resistance.