NiTi is a shape memory alloy, mostly employed in cardiovascular stents, orthopedic implants, orthodontic wires, micro-electromechanical systems and so on. The effective and net shape machining of NiTi is very critical for excellent response of this material in medical and other applications. The present experimental work on wire electrical discharge machining process identifies the influence of process parameters that affect the cutting rate, dimensional shift and surface roughness while machining of porous nickel–titanium (Ni40Ti60) alloy. Porous Ni40Ti60 alloy was produced in-house using powder metallurgy technique. Response surface methodology–based central composite rotatable design has been used for the planning of experiments on wire electrical discharge machining. Empirical relations have been developed between the process parameters (pulse on-time, pulse off-time, servo voltage and peak current) and response variables. Desirability approach has been used for optimizing the three response variables simultaneously. Confirmation experiments were also performed at the optimized settings and reflect a close agreement between the predicted and experimental values (percentage error varies from −6.13% to +6.85%). Using wire electrical discharge machining, NiTi alloy can be machined easily and successfully in single-cutting operation, but after the first cut in wire electrical discharge machining, a surface projection appears on work surface which is the unmachined material on work surface.

In this paper, wire electrical discharge machining of WC-Co composite is studied. Influence of taper angle, peak current, pulse-on time, pulse-off time, wire tension and dielectric flow rate are investigated for material removal rate (MRR) and surface roughness (SR) during intricate machining of a carbide block. In order to optimize MRR and SR simultaneously, grey relational analysis (GRA) is employed along with Taguchi method. Through GRA, grey relational grade is used as a performance index to determine the optimal setting of process parameters for multiple machining characteristics. Analysis of variance (ANOVA) shows that the taper angle and pulse-on time are the most significant parameters affecting the multiple machining characteristics. Confirmatory results, proves the potential of GRA to optimize process parameters successfully for multi-machining characteristics.

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Nitinol (NiTi) is categorized as a smart material which is highly recognized material for medical and other engineering applications. The behaviour of NiTi can be modified by altering the composition, modifying the porosity and applying external thermal and mechanical treatment. Due to high composition sensitivity, there are several impediments in fabrication of NiTi with conventional techniques which impel the use of additive manufacturing methods. But due to very high cost of equipments, these processes have not been commercialized till now. This paper presents a review on applications, manufacturing NiTi alloy and its various production routes from conventional to rapid prototyping, porous NiTi, effect of additives on properties of the alloy and its challenges.

In the present work, an experimental investigation on wire electrical discharge machining (WEDM) of Monel-400 has been presented. Monel-400 is a nickelcopper-based alloy, mostly employed in ships and corrosion-resisting applications. Four input WEDM parameters namely discharge current (Ip), pulse-on time (Ton), pulseoff time (Toff) and servo voltage (SV) have been investigated and modeled for two performance characteristics namely machining rate (MR) and surface roughness (SR). Effect of WEDM parameters has been discussed using response surface graphs. Using analysis of variance, quadratic model is found significant for MR while two factors interaction (2FI) model has been suggested for SR. To optimize multi-performance characteristics, desirability function has been employed. Corresponding to highest desirability, the optimal combination of discharge parameters is Ip: 103 A; Ton: 113 ls; Toff: 37 ls and SV: 50 V. The effect of discharge energy on surface morphology has also been examined. High discharge energy increases the extent of surface damage and results in large size and overlapped craters on machined surface. Low discharge energy and high value of Toff result in minimum defects on machined surface. Trim cutting operations were performed at low discharge energy using different wire offset values. Result shows that surface finish can be improved significantly after a single trim cut irrespective of high discharge energy in rough cut.

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Friction stir welding is a solid state welding in which two metal parts are joined without melting with the help of frictional heat generated between the work material and non-consumable tool. Because of the poor microstructure, cracks, porosity and residual stresses in fusion welding of aircraft aluminium alloys, friction stir welding is highly attractive for joints in aircraft structures. In the present work, using Taguchi's design of experiment method, combined effect of process parameters namely tool rotation speed, welding speed (or traverse speed of tool), tool pin profile and tool shoulder diameter have been investigated for the ultimate tensile strength and percentage elongation of friction stir welded joints of AA6082 alloy. Two similar sets of experiments were performed to prepare the friction stir welded joints; first samples of AA 6082-T6 (solution heat treated and artificially aged) were friction stir welded and second cryogenic treated AA6082 alloy were friction stir welded. A comparison in the optimal conditions of two sets of experiments has also been presented. In tempered aluminium alloy, three process parameters namely tool rotation, weld speed and tool shoulder diameter are significantly affecting ultimate tensile strength, while all four parameters are significant for percentage elongation. The influence of cryogenic treatment has also been noticed on two response characteristics. An integrated approach of Taguchi method, grey relational analysis and entropy measurement method have been utilized to obtain an optimal single setting of process parameters for two response characteristics. For the friction stir welded joint of AA6082-T6 (without cryogenic treatment), a single optimal setting of process parameters was obtained corresponding to tool rotation: 1200 r/min, weld speed: 35 mm/min, tool pin profile, threaded cylindrical and tool shoulder diameter: 16 mm. Similarly, the single optimal setting for cryogenic treated aluminium alloy (AA6082) was obtained corresponding to tool rotation: 1200 r/.min, weld speed: 35 mm/min, tool pin profile, cylindrical and tool shoulder diameter: 14 mm.

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