B. Ravisankar

Effect of Processing Routes on Microstructure and Mechanical Properties of 2014 Al Alloy Processed by Equal Channel Angular Pressing

Al-Cu alloy was deformed through equal channel angular pressing (ECAP) by routes A, B(subscript a), B(subscript c) and C up to 5 passes. ECAP was done using a 90o die for three different conditions, namely 1) as received, 2) solutionised at 768 K for 1 h and 3) solutionised at 768 K for 1 h + aged at 468 K for 5 h. The microstructure, microhardness and tensile strength were studied for all the three conditions and four routes. Significant improvement in hardness (HV 184 after five passes) and strength (602 MPa after three passes) was observed in solutionised and aged 2014 Al alloy deformed through route B(subscript c). Microstructure evolution was reasonably equiaxed in route B(subscript c). with aspect ratio of 1.6. Solutionised and aged 2014 Al alloy deformed through route B(subscript c) was identified to have better microstructure and mechanical property than the other processing routes and conditions.

Workability Study on 99.04% Pure Aluminum Processed by ECAP

This paper presents the workability of pure aluminum processed by equal channel angular pressing (ECAP) with different routes and the increasing number of passes. The experiments have been carried out to ECAP die using channel angle (2φ) of 90° and corner angle (ψ) of 20°. The ECAP samples were carried out up to three successive passes using Route A and C. The annealed and ECAPed samples were used to find out the mechanical property. Workability of the material is an important process parameter for the material to withstand up to initial cracking. The workability studies were looked into the normal compression tests on cylindrical sample machined from ECAP samples with a constant diameter of 20 mm with different aspect ratios 0.75, 1.0, and 1.5. Mechanical property and fractography studies were carried out before and after ECAP process. The observed results have been validated through Cockcroft ductile fracture criterion. An increased mechanical property with a little step down in formability of the consequent ECAP at the second and third passes of both the Routes was observed.

A Comparative Study of Commercially Pure Aluminum Processed by ECAP Using Conventional and New Die

Equal channel angular pressing (ECAP) is one of the techniques used in metal-forming processes but it runs into severe difficulties in die design. The role of friction in the die is important in regard to increasing workpiece internal stress while simultaneously reducing material strain hardening. Owing to internal stress, the workpiece fails in successive passes. This article throws light on the workability of commercially pure aluminum processed by ECAP using both conventional and new dies. The experiment was carried out for both circular and square samples of the same cross-sectional area. The samples were extruded by up to three passes in routes A and C. The ultimate tensile strength was 20% higher than in the conventional die samples. The workability of the ECAP samples is discussed from the compression test. The experimentally validated results are discussed using the Cockcroft fracture criterion. The enhanced mechanical properties, with a slight reduction in workability of the second and third passes in both routes, are discussed for both conventional and new die samples. The compressive strength is higher than the tensile strength in both dies. The new ECAP die achieved better mechanical properties than the conventional die samples and supports the same workability.

An Evaluation of Quality of Joints of Two Dissimilar Metals by Diffusion Bonding using Ultrasonic C Scan

Diffusion bonding of commercially available pure aluminum/copper was carried out between the temperatures of 400°C and 500°C for 60 min under the pressure of 5–15 MPa in vacuum. The effects of temperature and pressure on the microstructure of aluminum/copper diffusion bonded joints were analyzed. The interface micrographs of the bonded samples were observed in optical and scanning electron microscope (SEM) images. The soundness of the bond was evaluated by destructive and nondestructive (ultrasonic C scan) testing methods. The quality of the bonded joints was evaluated by the intensity of the echo and its images of ultrasonic testing and was correlated with destructive parameters such as the strength ratio. Chemical compositions of the interface and the fractured surface of the bonded samples were characterized by energy dispersive spectroscopy (EDS). EDS patterns were confirmed by the formation of the different compositions at the interface of the bonded samples. Better bonding characteristics were observed by diffusion bonding optimum parameters at 450°C with an applied pressure of 15 MPa for 60 min.

Densification of Al 5083 Mechanically Alloyed Powder by Equal Channel Angular Pressing

Equal channel angular pressing (ECAP), one of the most important methods in SPD, is used for the consolidation of mechanically alloyed Al 5083 powder. This paper mainly focuses on the densification of Al 5083 mechanically alloyed powder by ECAP with and without application of back pressure up to three passes with four different routes at room temperature. Aluminum can is used to encapsulate the powder. The particle size, crystallite size, microstructure and density were evaluated by scanning electron microscope and X-ray diffraction peak profile analysis. The crystallite size was measured by Williamson Hall analysis. Density and hardness were increased with increasing number of passes and upon sintering after ECAP. Good densification as well as good powder bonding was observed after three passes of ECAP.

Equal Channel Angular Pressing of an Aluminium Magnesium Alloy at Room Temperature

Severe plastic deformation affects grain size and its distribution to a great extent and it in turn has an impact on the mechanical properties of the specimen. This paper mainly focuses on the microstructure and mechanical properties of the Al 5083 processed by equal channel angular pressing at room temperature. The grain size, crystallite size and dislocation density were evaluated by transmission electron microscopy and X-ray diffraction peak profile analysis. The crystallite size and dislocation density were calculated by Williamson–Hall plot method. The mechanical properties such as hardness, tensile strength increase as the number of passes increases. Interestingly percentage of elongation also increases as the number of passes increases. The factors responsible for the change in mechanical properties were identified by electron diffraction and discussed.

Evaluation of Quality Diffusion Bonding in Similar Material (Cu/Cu) Using Ultrasonic ‘C’ Scan Testing Method

In the present study, diffusion bonding of Cu/Cu was carried out at 750 °C for 60min under uniaxial pressureof 5-15MPa in vacuum. The joints were evaluated by Microtensile testing and Ultrasonic testing. The bond qualities were assessed by destructive testing (strength ratio) and nondestructive ultrasonic C–scan testing method.The bond quality obtained by both the methods is correlated in a view to use the C scan for regular testing. The optimum condition for obtaining the best bonding characteristics is reported. The joint obtained by diffusion bonding at 750 °C and a applied pressure of 15MPa for 60min gives the best bonding characteristics.Keywords: diffusion bonding/welding, Interface, Ultrasonic nondestructive testing.

Effect of processing routes on evolution of texture heterogeneity in 2014 aluminium alloy deformed by equal channel angular pressing (ECAP)

Abstract In the present study, the effect of the processing routes (A, BA, BC and C) of equal channel angular pressing (ECAP) on texture evolution has been investigated for different initial microstructural conditions of the 2014 Al alloy. The present study also features the issue of heterogeneity in texture evolution along the thickness of the ECAP processed sample as a function of the processing routes. A stronger texture evolution was observed in the solution treated (ST) conditions for most of the processing routes (A, BA and BC except for C) due to the increased contribution from solid solution hardening during ECAP. A comparatively weak texture evolution is observed for as extruded+annealed and solutionised+aged conditions because of the strain scattering due to the fragmentation and dissolution of precipitates. The texture evolution along the thickness direction for ST samples suggests that the inherent heterogeneity of the ECAP process is minimised when processed via route C.

Microstructure and mechanical properties of 2014 Al alloy processed by equal channel angular pressing (ECAP)

The present work aims to investigate the microstructural evolution and mechanical behaviour of 2014 Al alloy upon equal channel angular pressing (ECAP) at ambient temperature. ECAP was carried using a 90° die through route A up to five passes. Microstructural and mechanical properties were compared for three different conditions namely: 1) as received; 2) homogenised at 768 K for 1 hr; 3) homogenised at 768 K for 1 hr + aged at 468 K for 5 hr. The improved strength and hardness of ECAPed 2014 Al homogenised at 768 K for 1 hr + aged at 468 K for 5 hr alloy was due to the precipitation hardening, grain refining and higher dislocation density. It was found that the grain size gradually decreased with number of passes and the average grain size was about 0.252 μm after five ECAP passes. The hardness and tensile strength of 2014 Al alloy remarkably increased up to 165 HV and 468 MPa, respectively. Correlation between tensile strength and hardness for the processing route A was also reported.

Mechanical Properties of Titanium–Titanium Boride Composites Through Nanoindentation and Ultrasonic Techniques — An Evaluation Perspective

In this work, the mechanical properties such as elastic moduli, shear moduli, and hardness of titanium–titanium boride composites with 20% and 40% of titanium boride reinforcements were estimated by ultrasonic and nanoindentation techniques. The estimated values obtained from the both measuring techniques are compared. The composites were processed by three powder metallurgical techniques such as spark plasma sintering, hot isostatic pressing, and vacuum sintering. The composites processed through spark plasma sintering and hot isostatic pressing showed better mechanical properties compared to the vacuum sintered composites. The effects of titanium boride reinforcements and their morphological influences on the mechanical properties are also described.