Analysis of metallurgical aspects and their role in processing and performance of superalloys: A review

Metallurgical processing factors like kinetic and thermodynamic parameters which are essential for modeling of γ′ phase precipitation have been studied. These parameters include γ′ solvus temperature, Gibbs free energy of dissociation of the γ matrix to form γ′, nucleation rate, effective diffusivity and interfacial energy. Nucleation methods and effect of cooling rate on the final phase structure have been analyzed. Co based  superalloys have been studied as a potential and promising material for aerospace applications. Effect of microporosity on the mechanical properties of Superalloys has also been analyzed.Keywords: Superalloys, Precipitation, Solidification, Gamma prime, Microsegregation, Microporosity

Studying the effect of variation in volume fractions of carbon fibres on mechanical and electrical properties of copper based composites

Metal Matrix Composites (MMC) belong to a class of weight efficient structural materials that are becoming popular in engineering applications especially in electronics, aerospace, aircraft, packaging and various other industries. This study focuses on the effect of varying carbon fiber wt. % on the mechanical properties of the Cu-C composite. The carbon fibers were coated with copper by electroless plating in order to increase the wettability of fibers with the copper matrix. Four compositions of copper based composite were developed by varying amount of carbon fibers. The yield strength decreases with increasing fiber size while the ultimate  tensile strength increases with increasing fiber size. Rockwell hardness test showed an increasing trend of hardness for increasing carbon fibers. The conductivity of Cu-C composite decreases by increasing carbon fibers content. Wear rate of Cu-C composite increases when carbon fiberscontent increases in the composite. SEM/EDX analysis revealed the size and distribution of fibers and indicated the fracture phenomenon.Keywords: Copper based Composites, Mechanical, Electrical and Wear Properties, Microstructur

Thermal, electrochemical and mechanical properties of shape memory alloy developed by a conventional processing route

A Cu based shape memory alloy (Cu-Al-Ni) having a composition 83% Cu, 14% Al, 3% Ni, was developed and studied to determine the shape memory effect. Powder of Cu, Al and Ni was melted in a pit furnace at about 15500C, and casted alloy was heat treated at 8500C for a period of 50 minutes followed by water quenching. Microstructure characterization of alloy (Cu-Al-Ni) was carried out to determine the pre-quenched (cast structure) and quenched martensitic structure. The microstructure analysis of developed samples showed needle like structure of quenched martensite after heat treatment. It has a very good resemblance with structure of casted shape memory alloy obtained from the vacuum induction process. The Vickers hardness test was also performed. Quenched microstructure with improved hardness than pre-quenched structure was observed.Keywords: Shape Memory Alloy, Microstructure, Mechanical Propertie

Photolithographic structuring of stretchable conductors and sub-kPa pressure sensors

NoThis paper presents a novel method to prepare stretchable conductors and pressure sensors based on the gold/polydimethylsiloxane (PDMS) system. The gold films were sputtered onto structured PDMS surfaces produced with a photolithographic surface treatment with the aim of reducing tensile strains in the gold film. Scanning electron microscopy (SEM) and atomic force microscopy analyses showed that these 3D patterns reduce cracks and delaminations in the gold film. Electrical measurements indicate that the patterns also protect the films against repeated tensile cycling, although the un-patterned samples remained conducting as well after the completion of 120 cycles. The extrapolated resistivity value of the patterned sample (4.5 × 10−5 Ωcm) compares well with previously published data. SEM micrographs indicate that the pattern features deflect the cracks and therefore toughen the gold film. However, x-ray photoelectron spectroscopy and contact angle analyses indicate that the patterning process also slightly modifies the surface chemistry. This patterning method was used to prepare capacitive strain gauges with pressure sensitivity (ΔZ/Z)/P of 0.14 kPa−1 in the sub-kPa regime. Such stretchable and potentially conformal low-pressure sensors have not been produced before and could prove advantageous for many smart fabric applications

Effects of supplementing different linoleic to α-linolenic acid ratios and vitamin a on performance and egg quality characteristics of laying hens during summer months

In present feeding trial, responses of laying hens, reared at high ambient temperature, to various dietary ratios of linoleic acid (LNA) to α-linolenic acid (ALA) and vitamin A levels for performance and egg characteristics were observed. A total of 360, 40-wk-old, Leghorn laying hens were fed on diets with various combinations of canola oil and linseed oil to achieve LNA to ALA dietary ratios of 20:1, 10:1, 4:1, 2:1, 1:1 and 1:2, each supplemented with 3000 IU or 10000 IU vitamin A/kg diet. The diets were fed ad libitum in a 6×2 factorial Completely Randomized Design that continued from 40 to 52 weeks of age. Standard managemental and housing conditions were provided to all hens. Feed intake, weight gain, egg production and egg quality traits were recorded during the trial on weekly basis. The results showed that decreasing dietary LNA to ALA ratio diet negatively affected (P0.05) by dietary treatments, with the exception of FCR per kg egg mass, egg weight and egg-shell thickness which were improved significantly (P<0.05) in hens fed on diets with lower LNA:ALA. Although dietary ratio of LNA to ALA of 4:1 or less could produce eggs by hens with high quantities of n-6 and n-3 poly unsaturated fatty acids that are characteristics of functional diets, the performance of laying hens in terms of body weight gain and egg-yolk percentage was slightly compromised, but, on overall- basis, performance of laying hens was similar among all LNA to ALA ratio in the diet. © 2019 MDPI AG