Materials Science Forum Vol. 969

Abstract: An investigation has been made to improve the properties of the friction stir welded (FSW) 6061-T6 aluminum alloys. A cryogenic thermal treatment is developed for the joints during welding and its effects on mechanical and metallurgical properties, and precipitates are evaluated at various welding parameters. The friction stir welded joints with cryogenic treatment attained the better properties than the without cryogenic treatment. The improvement of properties was attributed to the refinement of grain size and to the introduction of a reduction in the softening region of the welded joints. Under cryogenic cooling rates, joints were experienced to the low temperature environments and faster cooling rates, which are contributed to enhance the hardness of the stir zone and heat affected zone regions and the formation of fine grain structure in the stir zone. The results indicated that the formation of finer grains of less than 5 µm in the stir zone, which is smaller than the joints of without cryogenic treatment. Subsequently, mechanical properties drastically improved and the joints achieved a maximum joint efficiency of 74% of the base material

Abstract: Nickel based super alloy Inconel 718 is widely used in aerospace and power generation industries. The dissimilar joining of high strength tensile steel to Inconel 718 was joined using TIG welding. The welding current and travel speed parameters were varied to identify the suitable welding conditions for achieving highest joint strength. Microstructural characterization of the weldments were evaluated by using optical, scanning electron microscope and energy dispersive spectroscopy analysis. The fracture surfaces of the tensile tested joints were investigated under scanning electron microscope to reveal the mode of fracture and its influence on the performance of the joints. Microhardness and tensile tests were conducted to evaluate mechanical properties of the joints. The microstructure evolution revealed that the formation of precipitates at the fusion boundary between the weld zone and Inconel 718 alloy. The hardness of the fusion boundary area id higher than the base metal and fusion zone on Inconel 718 side, whereas the highest hardness obtained in heat affected zone on high tensile strength steel. The strength of the joints were failed in the weld zone along the deposition of the filler metal, which strength is similar to the joint strength. The elemental line scan analysis confirmed the formation of Nb and Ti rich precipitates in weld zone and along the fusion boundary of Inconel alloy.

Abstract: Advanced continuous polymer matrix composite materials provide considerable increase in flexural property values as compared with their bulk and monolithic counter parts. In this research work the effect of fiber orientation on the flexural strength of epoxy matrix composite materials reinforced with glass fiber was studied. Filament winding technique was employed for fabrication of composite with various fiber orientations. The flexural strength value of the glass fiber reinforced composite was comprehensively studied by means of three point bending flexural test and analysed by scanning electron microscopy. Experiments were conducted as per ASTM standards and it was concluded that reinforcement with 0^o orientation of glass fibers shown improved flexural strength as compared to 45^o and 90^o orientation of fibers.

Abstract: The present work deals with plastic deformation of 316L austenitic stainless steel (ASS) using room temperature rolling process. After solution treatment (annealing) as-received 316L ASS has been rolled for up to 90% of thickness reduction. To investigate the effect of processing on mechanical properties microstructural study, tensile and hardness tests have been conducted. The ultimate tensile strength has been improved from 767 MPa (before deformation) to 1420 MPa (after 90% deformation), and hardness value has been increased from 208 VHN (before deformation) to 449 VHN (after 90% reduction). Magnetic measurements and XRD characterization have been performed to confirm the formation of martensitic phase. Finite element analysis have also been simulated employing DEFORM-3D software to get the insight about deformation behavior. Keywords: Room temperature rolling, Finite Element Analysis, Mechanical properties, Austenitic stainless steel.

Abstract: In this work, Friction Stir Welding (FSW) of alloy 7039 was carried out in T4 temper and resulting microstructure and corrosion behaviour of developed weld were studied. FSW transformed the starting microstructure of base metal and formed stirred zone (SZ) and heat affected zone (HAZ) with varying microstructure and precipitate morphology. The observed zones in welded joints exhibited decreased protection to corrosion resistance than base metal. Dissolution of secondary precipitates in SZ and occurrence of precipitate free zones (PFZs) in HAZ enhanced susceptibility to corrosion of HAZ and weld nugget zone (WNZ) than base metal.

Abstract: A 3-D computational model was developed to examine the proton exchange membrane fuel cell (PEMFC) performance using Bio inspired (Bio channel) flow channel design bipolar plate. The model was developed using ANSYS FLUENT-15.0 software and simulations were carried out at 100 % humidity conditions. The parameters such as pressure distribution, hydrogen and oxygen concentrations and proton conductivity were briefly presented. The simulation results of bio channel are presented in the form of polarization curves. The results of a Bio channel compare with the conventional flow channel and observed that the bio channel gives a less pressure drop, uniform distribution of reactants and high cell voltage at a particular current density. From the observation from the polarization data, the bio channel performance was 20% higher than triple serpentine flow channel.

Abstract: A 3-D computational model was developed to examine the proton exchange membrane fuel cell (PEMFC) performance using Lung channel design bipolar plate. The model was developed using ANSYS FLUENT-15.0 software and simulations were carried out at 100 % humidity conditions. The parameters such as pressure distribution, hydrogen and oxygen concentrations and proton conductivity were briefly presented. The simulation results of Lung channel are presented in the form of polarization curves. The results of a Lung channel compare with the conventional flow channel and observed that the Lung channel gives a less pressure drop, uniform distribution of reactants and high cell voltage at a particular current density. From the observation from the polarization data, the Lung channel performance was 17% higher than triple serpentine flow channel. Keywords: Humidity conditions, Simulation, Lung channel, Polarization curves, Current density.

Abstract: Laser beam welding input conditions are greatly influence the quality of the welded joints and they have significant role on the controlling of their strength and metallurgical properties. The metallurgical properties and weld bead geometry and mechanical properties of the joints determine the quality of the joints. In this study, the fusion zone width, penetration, width of the heat affected zone and strength of the titanium alloy welds were investigated using laser welding process. The surface response methodology design is carried out for the experimental design by the development of regression equations. Analysis of variance (ANOVA) was used to check the validity of the model. In order to identify the significant parameters, student’s test is conducted. The obtained results from response surface methodology were compared with the experimental results and validated.

Abstract: High strength aluminum alloys will enhancing mechanical properties always plays a major role in controlling microstructure of cast and processed alloy. The desire for more efficient aircraft materials has fueled research of aluminum AA-2xxx and AA7xxx alloys. In these alloys were rolled at cold rolling and at cryorolling to 80 % thickness reductions and an attempt was made to evaluate the optical-microstructural variation and the variation in tensile properties of these aluminum alloys. Cryorolled alloy also exhibited better hardness and strength compared to cold alloy due to suppressed thermal recovery. Coldrolled alloy showed more necking percentage compared to cryorolled for rolling reductions of 80% and more formability was observed.

Abstract: Fabricating three dimensional shaped surfaces from flat sheet metals by laser forming, both out-of-plane and in-plane deformations are required. This article presents the modeling of coupling mechanism activated laser forming of sheet metals based on experimental data for prediction and optimization of bending and thickening deformations. Experiments were performed based on a central composite design of experiments on coupling mechanism based laser metal forming process considering the input process parameters like laser power, scan speed and spot diameter, bending and thickening were taken as the outputs. Neural network and neuro-fuzzy system-based models were developed to carry out both forward and inverse modeling of the laser metal forming process under the coupling mechanism. Multi-objective optimization based on the non-dominated sorting genetic algorithm was used to obtain multiple optimal solutions to achieve different amounts of out-of-plane and in-plane deformations. The proposed method could guide for a suitable selection of the process parameters to produce three-dimensional shapes utilizing coupling mechanism-based laser forming using multiple laser line heating.