P. P. Sinha

Processing and Characterization of Al-Cu-Li Alloy AA2195

The objective of the present study was to melt and cast AA2195 alloy in Vacuum Induction Melting (VIM) under dynamic inert atmosphere. These billets were homogenized and subsequently hot forged and rolled to sheets. The products in the form of sheets were subjected to T8 (Solution Treatment +WQ+CW+Aging) temper condition. Mechanical properties were evaluated at room temperature and correlated with microstructure. Highest mechanical properties obtained in T87 temper have been reported.

Reaction Synthesis and Homogenization Of γ + α2 Titanium Aluminide Alloys

Titanium aluminide alloys Ti – 48 at.% with additives of chromium, niobium and boron obtained by reaction synthesis from powder mixtures of the elements and subsequent heat treatment are studied. The alloys are subjected to chemical analysis, density and hardness measurements, light, scanning and transmission electron microscopy, energy dispersive local chemical analysis, and x-ray diffractometry. It is shown that the heat treatment affects positively the synthesis of titanium aluminides.

EFFECT OF CHROMIUM AND NIOBIUM ON THE KINETICS OF SYNTHESIS OF TITANIUM ALUMINIDE

The kinetics of the reaction of synthesis of titanium aluminide from binary (Ti – 48% Al), ternary (Ti – 48% Al – 2% Cr, Ti – 48% Al – 2% Nb) and quaternary (Ti – 48% Al – 2% Cr – 2% Nb) mixtures of elementary powders is studied. Differential scanning calorimetry in heating of the powder mixtures is used to determine the temperature and heat of formation of titanium aluminides and the kinetic parameter and activation energy in the Johnson – Mehl – Avrami equation.

Evaluation of Ti Aluminide Intermetallics Processed Through Reaction Synthesis

Titanium aluminides based on ΤΪ48Α1 with Cr and Nb additions has been made through reaction synthesis (RS) process. Development of various phases in RS and after homogenization has been studied through X-ray diffraction (XRD), optical microscopy (OM) and Transmission Electron Microscopy (TEM). Uniform distribution of elements was confirmed through elemental mapping, ED AX and hardness measurements. It is observed that, mainly Al3Ti phase forms during reaction synthesis and TiAl (γ) and Ti3Al (oc2) phases form after homogenization. Density of the product was measured and found to be nearly equal to theoretical density of the alloy. Improvement in hardness is observed after homogenization, which is found to be due to formation of γ. phases. A high temperature oxidation study of the ternary and quaternary alloy was carried out and it was noted that oxidation resistance of quaternary alloy is better than ternary alloy (with Cr). Processing aspects and properties of present alloys is compared with RS processed binary Ti alumnide.

Effect of Microsctucture on Mechanical Properties of Co-Cr-W-Ni Superalloy

Cobalt based Superalloy containing Tungsten, Nickel and Chromium as alloying elements, is extensively used in fabrication of high temperature components of launch vehicle systems. Microstructural variation with respect to grain size has an important role to play in mechanical properties of this alloy. Microstructural changes were incorporated by varying the heat treatment temperature and effect of such changes on the mechanical properties at room temperature as well as at high temperature is investigated. Increase in grain size and decrease in strength and ductility is observed for the alloy heat treated at relatively higher temperature.

Heat Treatment Study of γ + α2 Ti Aluminides Obtained through Reaction Synthesis and Hot Deformation

Abstract Ti aluminides based on γ + α2 has industrial importance due to its high temperature properties coupled with low density. Processing difficulty involved in this alloy has limited its application. Alternate processing route like reaction synthesis in combination with isothermal hot working has lot of potential. Further, heat treatment of hot worked material governs the properties of the alloy. In the present paper, heat treatment of reaction synthesized plus hot worked material has been studied to obtain desirable microstructure and phases. Five alloys of Ti48Al2Cr2Nb with minor addition of boron and Ni-P coated boron is made with two different particle size of Ti powder. Homogenized and worked alloy samples are heat treated to obtain two-phase microstructure useful for high temperature application. Heat treated samples are characterized for individual phases through optical microscopy, hardness measurement and electron microscopy. An attempt has been made to study the role of boron on development of various phases and microstructure.

A study of reaction kinetics in Al – 2% MWCNT composites

A composite obtained from pure aluminum and multiwall carbon nanotubes by mechanical milling in a high-power mill and ultrasonic mixing is studied. The apparent activation energy and the order of the reaction between carbon nanotubes and aluminum are determined using the Kissinger and Crane equations and differential scanning calorimetry under non-isothermal conditions.

Manufacturing of Inconel 718 Based Honeycomb Panels for Metallic Thermal Protection Systems

Metallic thermal protection system (MTPS) offers significant improvements over the ceramic based TPS for reentry applications. Space shuttle refurbishment time is estimated to be around 17000 man hours between flights. Metallic based TPS can be fabricated easily and provides wide range of design options for TPS. Adaptability and robustness of metallic thermal protection systems offers the potential for reusability. In this work, a unique manufacturing process has been evolved to realize light weight honeycomb panels through corrugation, laser welding and diffusion brazing of faceplates, where in 50 micron thick Inconel718 foil is used for making honeycomb core and 0.2mm thick Inconel718 foil as faceplates. The compression and three point bend test on these panels have shown no debond between faceplates and honeycomb core. 150x150x5mm size honeycomb panels were coated with YSZ and NiCrAlY based Thermal Barrier Coatings (TBC) and high temperature tests have shown thermal resistance of around 570 °C with front wall temperature of 1186 °C and back wall of 533 °C. Also these panels have been characterized for reusability by the testing of same panel at different heat flux levels. Though it is found that honeycomb panel has shown its integrity without debond a certain acceptable level of degradation in coating is observed. Thus Inconel718 based honeycomb panels with TBC coating are proved for use as thermal protection system for reusable launch vehicle systems.

Processing and Characterization of Al-Cu-Mg Alloy Rivets for Aerospace Applications

Al-Cu-Mg (Russian grade V65) alloys are used for riveting applications in aerospace industries due to their relatively high shear strength of the order of 25 kg/mm2 combined with a high plasticity. This paper presents the processing of V65 aluminium alloy rivets from wire rods. It was observed that wire rods which have not been intermittently annealed and having more than 25% cold working prior to heading operation, cracked on the free bulged surface of the head. In view of this, it is recommended that a maximum of 25% of cold work is allowed in the wire rods to be used for rivet fabrication to successfully realize defect free rivets.

Study on Ductility of Ti Aluminide Using Artificial Neural Network

Improvement of ductility at room temperature has been a major concern on processing and application of Ti aluminides over the years. Modifications in alloy chemistry of binary alloy (Ti48 Al) and processing conditions were suggested through experimental studies with limited success. Using the reported data, the present paper aims to optimize the experimental conditions through computational modeling using artificial neural network (ANN). Ductility database were prepared, and three parameters, namely, alloy type, grain size, and heat treatment cycle were selected for modeling. Additionally, ductility data were generated from the literature for training and validation of models on the basis of linearity and considering the primary effect of these three parameters. Model was trained and tested for three different datasets drawn from the generated data. Possibility of improving ductility by more than 5% is observed for multicomponent alloy with grain size of 10–50 μm following a multistep heat treatment cycle.