Papers by Keyword: Micro Hardness

Abstract: Solid-state diffusion bonding (DB) of Copper-Copper (Cu/Cu) was carried out under varying bonding parameters (time and temperature) in argon shielding gas environment. Initially, the bonding was performed at bonding temperatures of 800, 850, and 900 °C for 60 minutes. Secondly, the bonding was carried out at holding times of 90, 120, and 150 minutes at 900 °C. The microstructural and mechanical properties of the bonding interface were evaluated via lap shear and micro hardness tests, X-ray diffraction, and Optical microscopy. It was found that the optimal bonding parameters for the joint interface was 950 °C for 150 minutes, resulting in maximum shear strength of 133 MPa. The X-ray diffraction also shows the formation of solid solution of Cu without the formation of any intermetallic compounds (IMC). The micro hardness test revealed a maximum hardness of 89 HV at the joint interface. Optical microscopy shows the formation of voids at the joint interface take place due to the Kirkendall effect, which increased with higher temperatures for longer time, and cause a wide diffusion-affected zone (DAZ).

Abstract: Magnesium, a light weight alloy used in multiple engineering industrial applications because of its good Physical, Chemical and Thermal characteristics. Magnesium composites play an important role in partial or entire replacement of numerous alloys.This current work deals with Nano silicon carbide of about 100nm was incorporated with AZ91magnesium alloy through liquid state composite processing. Two samples are made using 0% Nano SiC and 3% Nano SiC and are characterized through tensile test in Universal Testing Machine, Micro hardness test in Vickers hardness tester and Microstructure in Optical Microscopy. From the study it was clear that there is a peak increase in hardness of about 36% when compared to as casted AZ91.

Abstract: The quality of the friction stir processed (FSPed) depends on the proper combination of processing parameters. The proper combination can only be found when a series of experiments have been conducted. However, the Taguchi technique was developed as a way of reducing numerous experiments that are time-consuming and costly. This paper reports on the optimization of parameters for the FSP that is conducted underwater (SFSP) and room temperature (NFSP). The Taguchi L18 method was employed in the design of experiments. The four factors used for the analysis had three factors with three-levels and one with two levels. The parameter combinations for SFSP were different from the combination found for NFSP. The level of parameter sensitivity was found to be influenced by the processing condition.

Abstract: The present work investigates the mechanical characterization of aluminium alloy (AA) 6061 based hybrid nanometal matrix composites (MMCs) fabricated using conventional stir casting process. Two compositions viz., AA6061+1.5 wt.% B₄C+0.5 wt.% SiC (Hybrid A) and AA6061+1.5 wt.% B₄C+1.5 wt.% SiC (Hybrid B) was prepared and its mechanical properties such as microhardness, tensile, compressive, flexural and impact strength were investigated to compare with unreinforced AA6061. SiC and B₄C ceramic particles (purity 99.89%) of average particle size of 50 nm were used as reinforcements. Significant enhancement in microhardness of 30.2% and 31.02% for hybrid A and B are observed respectively. The ultimate tensile strength (UTS) increased by 10.72% and 16.55% for hybrid A and B respectively. Improved interaction because of the enhanced surface to volume ratio at the interface resulted in improvement of mechanical properties. Field emission scanning electron microscopy (FESEM) of the fractured surface shows brittle fracture because of the incorporation of the ceramic reinforcements in the matrix material. The developed AA6061/SiC/B­₄C hybrid nanocomposites show improved mechanical properties for high-performance structural applications.

Abstract: Titanium-Nickel pre-alloyed powder was reinforced with Nano-Silica in 2%, 4% , 6% and 8 wt. % due to effectiveness of Nanoscale ceramic Reinforcement in improving the properties of Metals and Alloys. The compositions of the Pre-Alloyed powders and Nano Silica Approximately 50 nm in diameter and spherical in shape were weighed and mixed in Planetary Ball Mill followed by compaction at 50 MPa using a Uniaxial Compaction machine The green pellets obtained were sintered in Argon Environment for 5 hrs and allowed to furnace cool. The pellets were then sectioned through their cross-section for slices 3 mm thick followed by Cold-mounting and Soldering followed by cold mounting additionally. The Samples were analyzed via X-Ray Diffraction (XRD) for phase distribution as a function of variation in nano-Silica reinforcements and Microstructural analysis was performed via Optical Microscope. The effect of Volume percentage on the densification was determined via Archimedes principle and Micro-Vickers hardness was used for mechanical Evaluation. The Electrochemical Properties were evaluated using Potentio-Dynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) in neutral salt solution (3.5% NaCl). The results indicated increasing dissolution of the TiNi phase into intermetallic Titanium-rich and Ni-rich phases in the matrix and hardening due to the Nano-Silica effect of Grain Boundary impingement and phase dissolution of Equiatomic phase and mixed behavior in Corrosion properties as determined by the electrochemical techniques whereas densification decreased due to poor plasticity of Nano-Silica and hinderance in diffusion during the sintering process.

Abstract: The glass micro balls based on glass domestic waste for road construction were obtained. Glass micro balls will reduce the contamination of road marking and increase its light-reflective ability at night. Colorless and colored container glass, as well as lead crystal, was chosen as the starting material for producing glass micro balls. An electric arc plasmotron UPU-8M was used to produce glass micro balls. Pre-crushed fractionated glass together with plasma-forming gas – argon was fed to the powder feeder and from the feeder to the plasma burner. Under the influence of high plasma temperatures, about 9000-12000K, the particles were melted, followed by cooling in the outgoing flow of plasma-forming gases. Due to high-temperature plasma exposure, partial evaporation of alkaline oxides and lead oxide occurred. Glass micro balls were enriched with the oxides of silicon, aluminum and calcium. This helped to increase the acid and alkali resistance of glass micro balls. The micro hardness, density, and refractive index of glass micro balls were studied. It is shown that glass micro balls have an ideal spherical shape and are x-ray amorphous. Glass micro balls are recommended for use in road construction as a reflective element of road marking.

Abstract: TiC – Fe composite coating was produced on AISI 1020 steel by the tungsten inert gas (TIG) cladding process to increase the hardness and wear resistance properties of the substrate. In this paper authors have investigated the effect of process parameters on the microstructure and hardness value of the coated layer. In this TIG cladding process the variable parameter is only current, whereas the other parameters such as scanning speed, standoff distance, and voltage and gas flow rate are fixed. Fe and TiC powders were mixed in the proper ratio of 80wt% - 20wt% and 90wt% - 10wt% respectively. The microstructure and micro-hardness value of the samples were investigated by the scanning electron microscope (SEM) and Vickers micro hardness tester. The result of SEM shows the distribution of the coating powder in the cladded zone. Micro hardness profile shows the variation of the hardness value in the cladded zone as well as in the substrate. The hardness value decreases with increase in distance from top surface of the cladded layer, which is due to difference in cooling rate. Also, the hardness value of cladded layer decreases with increase in current from 140A to 150A. The maximum hardness value of cladded layer was achieved as 262 HV_0.05 with 140A current and composition of 90 wt.% - 10wt% (Fe - TiC), which was nearly two times higher than that of the as received AISI 1020 steel substrate. Keywords TIG, Microstructure, Micro hardness, Titanium Carbide (TiC), Iron (Fe) powder.

Abstract: In this project, the nominal glass composition with the form of (55-x) H₃BO₃-45ZnO-xY₂O₃ (x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) are synthesized by melt quenching techniques. The effect of Y₂O₃ on physical, mechanical and structural properties of glasses have been investigated using different characterization techniques. The parameters like density, molar volume and oxygen packing density have been calculated. Based on the micro hardness study, it has showed the decreasing trend from 518.80 N.mm^-2 to 453.13 N.mm^-2 with an increasing of Y₂O₃ content from 0.0 mol% to 2.5 mol%. The structural features of the yttrium oxide doped zinc borate glass were studied via X-Ray Diffraction (XRD) to confirm the amorphous nature of glass and Fourier Transforms Infrared Spectroscopy (FTIR) has been done to obtain the band positions and functional groups. FTIR spectral studies were recorded in the 400-4000 cm^-1 wavenumber range at room temperature.

Abstract: According to the dynamic characteristics of the electrochemical system, according to V.F. Molchanov, it is possible to optimize the composition of chroming electrolyte and predict the properties of chromium deposits depending on the mode of deposition and the transition time. The possibility of using the transition time for the formation of the cathode surface colloid-dispersion film to study the chemical composition of the chroming solution is considered. The chemical composition can be optimized by the position of the maxima and minima on the polarization curves. An electrochemical cell can be described as a system by a differential equation, the form of which is determined by its internal structure, which varies with electrolysis conditions. The properties of the system are evaluated by a number of factors: the time of the transition process, forcing, attenuation, and the quality factor. This approach is used to develop a low-concentration chroming electrolyte with organic additives. Analytical dependences of chromium yield on current, micro hardness, roughness and deposition rate on deposition conditions are obtained. Chroming on non-stationary modes allows the most effective influence on the structure and physical-mechanical properties of coatings. When changing electrolysis parameters, it is possible to influence the structure and physical-mechanical properties of coatings, to obtain various functional chromium coatings with specified characteristics (adjustable micro hardness in thickness, porosity, internal stresses, corrosion resistance, wear resistance, roughness) from a single electrolyte. The use of a low-concentration electrolyte together with non-stationary deposition modes makes possible to increase the chromium current yield, covering and dissipative ability of the electrolyte, deposition rate, producibility and environmental friendliness of the process, and to reduce hydrogenation. The electrolyte with crystal violet additives has an increased current output (up to 28 %), an extended range of obtaining wear-resistant coatings up to 240 A / dm², a high deposition rate of up to 2.5 μm / min, an increased micro hardness by 100-300 kg / mm², reduced toxicity, a decreased absorbed hydrogen level at 500-700 cm³ per 100 grams of chrome coating and internal stresses at 600-950 kg / mm2.

Abstract: In the paper is presented the analysis of tool steel used for making a knife for a mill for grinding plants. The material used for the knife is about 1% carbon and is symbolized by RWL34. To improve the properties of the material, especially the knife cut, a thermal treatment were made and was measured hardness, wear resistance and microscopic analyzes of the metal. The paper presents the values of the mechanical properties on the initial sample, on the hardening sample and on the sample subjected to a hardening and tempering treatment, as well as the graphs related to them. The next step in finalizing the analysis of the grinder mill knife is to study the behavior in operation and the possible corrections that should be made.