Vikas Goyat

NiCr20TiAl is a nickel based superalloy widely used in high temperature applications such as engine valves and turbine blades, where resistance to chemical attack and thermal degradation is critical. This study presents an experimental investigation into the relationship between heat treatment, microstructure, mechanical properties and fracture behavior of NiCr20TiAl. Samples were subjected to various heat treatment regimes, followed by microstructural characterization using optical microscopy, hardness and tensile testing at both room and elevated temperatures. Fractographic analysis was conducted using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to identify fracture mechanisms and the role of precipitates in fracture initiation. Results show that fine grains with annealing twins were observed up to a solution annealing temperature of 1080°C, beyond which grain coarsening occurred. Aging promoted significant precipitation along grain boundaries with negligible grain growth. The optimal mechanical properties were observed for the T4 (1040°C solution annealed) and T11conditions, with T11 (1040°C solution annealed and aged) exhibiting the highest tensile strength (1283 MPa) and hardness (368 HV), albeit with slightly reduced ductility. Hardness improved by aging around 80%, with a maximum value observed for T11 as 368 HV. At elevated temperatures, aged samples maintained superior properties up to 700°C, beyond which performance declined. The optimized heat treatment of 1040°C solution annealing and aging at 700°C proved most suitable for high temperature applications below 700°C.

This study delves into investigating, modeling, and optimizing the Equal Channel Angular Pressing (ECAP) process parameters for Cu–0.7%Te in order to enhance its mechanical and microstructural properties with minimum impact on electrical properties using the Response Surface Methodology (RSM). The ECAP die channel angle (90°–110°), number of passes (4 –12), and processing temperature (25°C–425°C) are chosen to see their critical influence on mechanical (hardness and tensile strength), microstructural, and electrical (conductivity) properties. The experiments are designed as per the RSM face centered design, and the model of each response was prepared. The optimal set of parameters was obtained by the prepared RSM model for maximum mechanical and electrical properties and minimum grain size. The verification test was conducted using the nearest feasible optimized parameters. The obtained result of the verification test is compared with the parent unprocessed sample and discussed in detail using optical, Electron Backscattered Diffraction (EBSD), and Transmission Electron Microscopy (TEM). The verification analysis shows that the obtained results are within the 95% confidence interval of the predicted results of the RSM model, which signifies the accuracy and reliability of the prepared model.

The current trend of reducing the size of electronic devices in the industry has extensively increased the demand for effective heat dissipation, thereby intensifying the need for high-performance heat-dissipating devices. A promising approach to solve this challenge is the use of single-phase (SP), two-phase (TP), and supercritical fluids in micro-channels (MCs). Two-phase cooling is applicable only to those devices in which the tip temperature is high enough to allow the cooling fluid to convert into a two-phase state. In all other cases, only single-phase cooling can be utilized. In this work, numerical and experimental investigations on MC have been performed using water as the working fluid to predict TP behavior and heat dissipation from electronic devices using SP and TP flow. A numerical model of flow boiling heat transfer was developed based on conservation equations, which is solved to identify the existence of single and two-phase regions in the MC and to study the variation of pressure along its length at different heating powers. Further, experiments were performed in both SP and TP conditions to observe the nature of flow regimes and the impact of various parameters on effective heat dissipation through MCs well as temperature distribution. Numerical results were validated with experimental results, which showed good agreement. Several experiments were also carried out to develop an empirical correlation between mass flow rate and heat power to maintain the electronic device temperature below 40 °C. The developed correlation is experimentally validated at three different heat powers 6 W, 8 W and 10 W.

Purpose: Inverse distance weighted (IDW) functions are utilized to make models of heterogenous materials such as functionally graded materials (FGM) in computer aided design (CAD). However, the use of IDW function based FGM for stress concentration reduction is scarcely available in the literature. The present work aims to analyze and reduce the stress concentration around a circular hole in IDW function-based finite FGM panel under biaxial loading.Design/methodology/approach: Extended finite element method (XFEM) model was prepared using MATLAB to investigate the effect of geometrical and material parameters on the stress concentration factor (SCF). The obtained results of IDW FGM are compared with homogeneous material as well as two different FGMs based on the power-law function.Findings: It was observed that the IDW function based FGM is simple in material modeling, conformal with all domain boundaries and shows lower stress concentration in comparison with the homogeneous material case. While comparing IDW FGM with power-law based FGMs, it was observed that the IDW FGM has least values of stress concentration for low d/W (diameter of the hole to panel width ratio) and is comparable with power-law based FGMs for high d/W.Originality/value: It can be stated that IDW FGM is highly suitable for stress concentration reduction in finite panels with d/W = 0.5, which can further be intended for obtaining optimum hole and panel designs.

The present work aims to study the stress concentration factor (SCF) reduction using different functionally graded materials (FGMs) layer around the circular hole in an infinite homogeneous material panel for different load conditions. Young’s modulu