Materials Science Forum Vol. 969

Abstract: Current study deals with the microstructural characterization of five different plates of steel with carbon concentration ranging from ultra-low to moderately high. Phase analysis was carried out using XRD technique. The XRD results were analyzed through Rietveld refinement and Williamson Hall plots. Rietveld refinement was carried out to understand the effect of carbon concentration on the lattice parameters of the above steel samples in as-received condition and also after deformation under uni-axial tensile loading. Lattice parameters obtained from refinement showed the strong dependence on carbon concentration of the given steels. But the failed specimens showed somewhat complex results as Spheroidized high carbon steel, Low carbon steel and IF steel showed an increase in lattice parameter whereas Medium carbon steel and Microalloyed steel showed a contraction in lattice parameter. Williamson Hall plot gave the crystallite size, microstrain and dislocation density in the steels. For IF and Microalloyed steels the dislocation density in the material is found to be higher after deformation whereas dislocation density decreased in Spheroidized high carbon steel, Medium carbon steel and Low carbon steel.

Abstract: Three phase composites that consists of piezoelectric and piezomagnetic fibers embedded inan elastic matrix phase exhibits new product properties such as magnetoelectric effect, pyroelectric andpyromagnetic effect, which are absent in individual phases. In this work, simple analytical expressionsare developed based on strength of materials approach to find these effective coupling coefficients. In amicro scale rectangular representative volume element (RVE) of a layered type three phase composite,series connectivity is assumed between fiber and matrix layers along transverse direction and parallelconnectivity is assumed along longitudinal direction. The analytical model is validated with otherhomogenisation methods and effective property variation of BaTiO₃-CoFe₂O₄-Epoxy composite andLiNbO₃-CoFe₂O₄- Epoxy composite are discussed.

Abstract: The anodic potentiodynamic polarization behavior of various grades of cold-worked (rolling and machining) austenitic stainless steels were studied. Deformed specimens were characterized by Electron backscattered diffraction (EBSD) and Fourier transform infrared spectroscopy (FTIR)-imaging. The FTIR-imaging was used to quantify chromium oxide (Cr₂O₃) spectra. It was observed, average area under Cr₂O₃ spectra was decreased with increase in cold -working. The certain regions in deformed microstructure showed higher value of area under Cr₂O₃ spectra, indicated stability of passivation film that needs to be explored. There was no microstructurally different between machined specimens.

Abstract: AA2014 is a heat treatable aluminium alloy found its application in light weight structures owing to its superior strength to weight ratio. The alloy was welded with automatic gas tungsten arc welding. The microstructure and mechanical properties of each zone such as parent metal (PM), heat affected zone (HAZ) and fusion zone (FZ) of the weldment were studied using optical microscopy, microhardness survey and micro-tensile testing. The PM with elongated grains with evenly distributed Al₂Cu phases showed a tensile strength of 456 MPa and 24% elongation; the HAZ and FZ offered a reduction in strength and ductility. The grain coarsening with segregation of continuous string of Al₂Cu along grain boundaries in HAZ and the formation of coarse dendritic grains with continuous network of brittle Al₂Cu and a minor fraction of porosity at interdendrite in FZ were attribured to the observed strength reduction in these regions. Keywords: AA2014 alloy; gas tungsten arc welding; optical microscopy; microhardness; micro-tensile testing.

Abstract: Friction stir welding (FSW), a solid-state joining process is extensively using in the welding of aluminum alloy sheets. In order to save energy and reduce emission, lightweight materials like aluminum alloys were introduced into steel car body, which requires the development of effective joining processes. In the present study, welding was carried out in two different conditions, in the air (CFSW) and underwater (UWFSW) at various welding speeds to weld 5052-O aluminum alloy sheets. The effect of UWFSW on microstructural developments, mechanical properties, and formability was evaluated and compared. Grain refinement is an important opportunity to improve the mechanical properties of FS welds. Considerable grain refinement was obtained in UWFSW joints, which is smaller than that in the CFSW joints. The results indicated an increase in tensile strength, hardness, the percentage of elongation, and formability of UWFSW weld sheets. The results of the tensile test, hardness test, microstructure and fractography as in good correlation with improved properties.

Abstract: Ni based super alloy 617 is widely used in transition liners in both aircraft and land-based gas turbines, power plant applications because of its high temperature strength, oxidation resistance and creep properties. Ni based alloys are highly susceptible to hot cracking like solidification and liquation racking issues. In this present work, the susceptibility of alloy 617 to solidification cracking is studied based on the varestraint test. Results of this weldability test proved that in addition to the solidification cracking susceptibility alloy 617 is prone to liquation cracking also. Keywords: Varestraint test, Alloy 617, Solidification cracking, Liquidation cracking.

Abstract: The objective of this research work is to study the influence of different in-process contact materials (steel, aluminium and brass) and building contact materials (concrete and wood), and its hardness on the impact sensitivity of matchhead composition. The BAM fall hammer was used for measurement of impact sensitivity. The result demonstrated that the in-process and building contact materials, and its hardness imparted variation to the sensitivity between 3.33J and 15.892J. The least LIE was found at 3.33J for the steel at 115 HRB and 117 HRB; 3.72J for aluminium at 53 HRB; 4.7J for brass at 82 HRB; 12.16J for concrete at 35 RHN, and 13.14J for wood at 16 HRB. The limited impact energy was lowest when there was contact between steel and steel as in-process material and contact between concrete and concrete as building contact material. The impact sensitivity was higher for material with higher hardness for all building and in-process contact materials. Brass and wood is suggested to be used as process and building materials in order to reduce the risk of explosions due to impact sensitivity.

Abstract: In the present study, D-optimal based mixture design of experiments (DoE) is used to find the optimum powder mixture for High Velocity Oxygen Fuel (HVOF) coating. Twenty five experimental trials are performed by varying the powder mixtures based on mixture design. Cr₃C₂, Ni, Cr, B, Si powder mixtures are deposited on Inconel 718 substrate by HVOF process.The responses porosity and hardness are determined by the cross-sectioning the specimens.The effect of powder mixtures on coated samples are characterized by X-ray diffraction, optical microscope, Vickers hardness tester and Scanning electron microscope.The optimal powder mixture is determined to obtain minimum porosity and maximum hardness and the confirmatory experiment confirms with the predicted results. From the analysis it is observed that Cr₃C₂, Ni and Cr are the major factor which influences the porosity and hardness followed by B and Si respectively.

Abstract: This research work aims to understand the influence of temperature (upto 80°C) on the impact sensitivity of matchhead composition with various process contact materials (Steel, aluminium, brass) and to find out the critical temperature for process safety. The BAM fall hammer was modified with a heating element for the measurement of impact sensitivity. The Limiting Impact Energy (LIE) at ambient temperature condition with steel surface on the top and bottom was found to be 3.73J. The lowest critical temperature was found to be 60.14°C for the matchhead composition when it is in contact with steel, which was used as the contact material for both top and bottom.