Materials Science Forum Vol. 978

Abstract: Electric discharge machining (EDM) is a spark erosion process widely used to machine difficult-to-cut material by conventional machining method. The major elements of EDM process are work piece, electrode and dielectric fluid. In this work, an attempt is made to investigate vegetable oil as dielectric fluid and their process performance for machining of Inconel 800 in EDM process. The effects of dielectric fluids are investigated with vegetable oils and conventional dielectric fluid namely Sunflower oil and Kerosene respectively. The important input variables considered in this study are pulse on/off time, current and voltage. Three levels of energy setting are employed for machining with selected dielectric fluids. The output parameters are considered tool wear rate (TWR), material removal rate (MRR) and surface roughness (SR). In the present study effect of vegetable oil as dielectric fluid and the results are compared with conventional dielectric fluid. The result revealed that vegetable oils are successfully employed as dielectric fluids and they are having similar dielectric properties and erosion mechanism compared to conventional dielectric fluid. This proposed vegetable oil based dielectric fluids showed higher MRR than conventional dielectric. It shows vegetable oils have similar dielectric properties compared with conventional dielectric and it is possible to replace as dielectric fluid in EDM process.

Abstract: This article presents the effect of weld zone shapes on microstructure and tensile properties of weld joints in friction stir welding. Experiments are conducted using four different tool pin profiles that are cylindrical, conical, cylindrical-conical and stepped-conical for analysing the weld zone shape. The weld zone shape properties are defined by characteristic length. Grain size and mode of fracture surface behavior are analysed by optical microscope and scanning microscope respectively and tensile strength is measured by universal testing machine. It is also observed that the weld zone shape of all pin profile tool is vase shape. In which, cylindrical, conical and cylindrical-conical pin profile tools produce basin dominant vase shape and stepped-conical pin profile tool produces cylinder dominant vase shape. The experimental result shows that the weld joint fabricated by stepped-conical pin profile tool produces the smallest grain, good ductile fracture mode and highest tensile properties as compared to other pin profile tool. This analysis shows that cylinder dominant vase shape produces high tensile properties and enhance ductile fracture mode in the weld joint.

Abstract: Occurrence of defects like crack on the surface of the cast products has long been recognized as a critical challenge for steelmakers in the continuous casting. Cracks on the surface can severely reduce yield and required further operations like salvage and scarfing. Depending on the severity of defect slabs can be diverted or in worst cases a slab can be rejected altogether if the defect cannot be removed by surface conditioning. Rourkela Steel Plant (RSP) of Steel Authority of India Limited (SAIL) produces continuously cast slabs as feed material for plate mills and hot strip mill. Sometimes the slabs produced through continuous casting are faced issues intermittently due to presence surface defects like midface longitudinal cracks (LC) and transverse edge crack (EC) etc. A systematic investigation of the operating parameters of these casters e.g. monitoring of oscillation parameters, slabs and mould flux, simulation and analysis of fluid flow inside mould, steel chemistry and role of dissolve gases in steel. Based on the investigation critical parameters responsible for crack formation have been identified and key areas identified where modification need to be done. Modifications has been done in terms of mould flux addition practice, optimization of the grade chemistry, optimization of process route, optimization of casting speed, checking of strand thermal profile, mould & machine allignment etc. It was observed that the crack incidences are significantly lower after the modifications were done.

Abstract: This presented article focuses on surface characterization and assessing the satisfactory machining condition of WEDMed Inconel 625. This work material has been received remarkable attention to the industrial and academic organization for its end use applications. WEDM is well-known machining process for intricate shape cutting and machining hard materials. The experimental design was planned according to L₂₇ orthogonal array (OA), by varying controllable process parameter (i.e. Wire-Tension, Wire-speed, Flushing-Pressure, Discharge-Current and Spark-on Time), each parameter varied at four discrete levels, within the selected parametric domain. WEDMed surfaces have been investigated with a focus to the surface characterization of selected machined surface through captured images from scanning electron microscope (SEM). Eventually, multi-response optimization of process parameters was sought by using a combination of nonlinear regression modelling, fuzzy inference system (FIS) with Teaching Learning-Based Optimization (TLBO) algorithm. The obtained TLBO result was compared with the Genetic algorithm (GA). The results show that optimization algorithms are effective tools for getting satisfactory optimal machining conditions during WEDM process of Inconel 625.

Abstract: Machining has been one of the most sort of process for realizing different products. It has significant role in the value additions process. Machining is one of the production process where material is removed from the parent material to realize the final part or component. Among machining, the well known machining processes are turning, milling, shaping, grinding and non-conventional machining processes like electric discharge machining, ultrasonic machining, chemical machining etc. The fundamental of all these processes being material removal in the form of chips using a tool either in contact or not in contact. In the present work, milling is being taken for study Finite element analysis is being used as a tool to understand the different phenomenon that underlies the machining processes. Of late, the machining induced residual stresses is of great interest to the researchers since the residual stresses have an impact on the functional performances. The present work is to model the milling process to predict the forces and residual stresses using finite element method. Unlike many researchers, the authors have attempted to develop oblique cutting model rather than an orthogonal cutting model. The present work was carried out on AISI 1045 steel.

Abstract: Single pulsed laser melting in a cylindrical titanium alloy work piece is studied numerically using an axisymmetric model. Finite volume method and Tri-Diagonal Matrix Algorithm (TDMA) are used for discretization of the energy equation and solving the resulting algebraic equation respectively in order to obtain temperature distribution inside the computational domain. Heat losses from the irradiated surface takes place through convection and radiation and other surfaces are kept insulated. A volumetric and Gaussian laser is irradiated on the work piece. Validation of the present model with the existing literature is done first and the results agree very well. Then, the detailed transport phenomena during the laser melting process is studied using the model. The enthalpy porosity technique is used track the melt pool shape and size. The role of natural convection and Marangoni convection in controlling the shape of melt pool is discussed. Maximum temperature results at domain centre and it then decreases exponentially along the axial and radial direction of the work piece because of Gaussian nature of the pulse. The numerical results obtained can provide the direction to develop models for all type of laser applications used in the industry.

Abstract: Micro-electrochemical discharge machining is hybrid machining process which is based on combined principle of electro discharge machining and electro chemical machining. It is suitable for machining of both conductive as well as non-conductive materials. In this study a micro hole drilled on Ti-6Al-4V as work piece by varying machining parameters like electrolyte concentration, voltage and duty factor at three different levels. Orthogonal array L9 considered for design and performing experiments. The Grey relation analysis (GRA) was performed to optimize the output parameters i.e. material removal rate (MRR) and hole tapper angle (HTA). The result reveals that voltage was the most significant factor for both MRR and HTA followed by electrolyte concentration and duty factor. The maximum MRR and minimum taper angle are 1.50 mg/min and 0.98 ° obtained respectively. The GRA show optimal machining parameters at electrolyte concentration 3M, voltage 40 V and duty factor 25% respectively.

Abstract: In this study, multi objective optimization for improving the joining characteristics of dissimilar AA5083-AA6061 alloys during FSW has been presented. Tool rotational speed, feed and tilt angle are the input parameters whereas tensile strength and hardness are the responses. Experiments are planned and conducted as per Taguchi L₉ orthogonal array. Main effects plot and contour plot discloses the parametric influence over the responses. Hybrid GRA and PCA were deployed as tools to perform multi objective optimization. Results pointed out the fact that tilt angle played vital role in affecting the responses followed by feed and tool rotational speed. The optimum parametric settings obtained are speed 710 rpm, Feed 50 mm/rev, and Tilt angle 2^o.

Abstract: In the current work, wear behavior of plasma processed LM6 alloy is investigated. LM6 alloy was prepared by plasma technique. The samples were aged at 350^°C & 450^°C for 2 hours followed by water quenching. A comparative study of the metallographic structure and properties viz. hardness, density and wear of the non-heat and heat treated alloy samples were carried out. A very fine lamellar structure is observed in case of 450^°C heat treated samples than that of sample heat treated at 350^°C and non-heat treated samples. Highest hardness value of 68.11 VHN is observed with the sample heat treated at 450^°C. Density is found to be the lowest in non-heat treated samples and it increases with increasing heat treatment temperature. Wear experiments were carried on a pin-on-disc set up (of Ducom make), varying applied loads (between 10-40Newton and varying sliding speed (from 0.94 m. s^-1 to 2. 83m.s^-1). Maximum wear resistance is observed with the specimen heat treated at 450^°C.

Abstract: Materials performance plays a pivotal role to the smooth operation of present and future nuclear energy systems operating in severe irradiation environment in reactors. Therefore selection of structural materials with the desired properties is vital for this field of applications. The present work reports the effect of milling time during mechanical alloying of a novel Oxide Dispersed metal matrix composite consisting of multi-component AlCrFeMnNi high entropy alloy system with minor addition of Partially Stabilized Zirconia (PSZ) (1 wt.%). The main focus of this work is to understand the phase stability behaviour during mechanical alloying. High Entropy Alloy AlCrFeMnNi with Partially Stabilized Zirconia (PSZ) as Dispersoid phase was prepared by mechanical alloying. For study of phases, milled powder was investigated through X-Ray diffraction technique followed by Scanning Electron Microscopy for microstructural morphology. The study reveals that PSZ Dispersed AlCrFeMnNi alloy mainly consists of BCC (Fe Type) and FCC (Ni Type) mixed structure. At the end of 30 h lattice strain and crystallite size were measured to be 0.738 % and 13 nm respectively.