A. Sili

A Weldability Study of Al–Cu–Li 2198 Alloy

Al–Cu–Li alloys, conceived for automotive and aeronautic applications thanks to the high mechanical resistance/density ratio, exhibit weldability issues common to all light alloys. In this paper, the weldability of Al–Cu–Li 2198 alloy was studied by comparing features of welds carried out by two processes, the traditional arc welding and the friction stir welding (FSW). Welded joints were submitted to optical and SEM metallographic examinations with EDS microanalysis measurements. Mechanical characteristics were evaluated through microhardness tests and the instrumented indentation test FIMEC (Flat-top cylinder Indenter for MEchanical Characterization).

CHACTERIZATION OF CU TUBE FILLED WITH AL ALLOY FOAM BY MEANS OF X-RAY COMPUTER TOMOGRAPHY

Copper tubes filled with aluminium foams were prepared by directly foaming metal powder compacts inside them. Compressive behaviour and foam-shell interface, that characterizes mechanical properties of reinforced tubes, were investigated by means of variable focus X-ray computer tomography. Compression tests were performed on empty and filled samples at increasing deformation steps: at each stage the samples were observed by tomography. A geometric evaluation of porosity on 2D sections was performed by calculating, for each pore, its area, equivalent diameter and circularity.

Mechanical and metallurgical characterization of 8090 Al–Li alloy welded joints

The properties of Al–Li alloys have been extensively studied recently for structural applications in automotive and aerospace industry, thanks to their lower density and enhanced modulus of elasticity. In common with many Al alloys, one of the main issues is the loss of toughness and soundness of welded joints consequent upon welding operations, in particular, possible cracking in the weld metal and metallurgical modifications induced in the heat-affected zone. In this work, welding trials were carried out on 8090 Al–Li plates welded by electric arc, using a 5% Mg filler metal. Joints were mechanically and metallurgically characterized through tensile and microhardness tests, optical and scanning electron microscopy, and fractography on both welded and unwelded tensile specimens. Energy dispersive spectroscopy (EDS) measurements were also performed to evaluate chemical composition locally and determine the nature of precipitates.

Characterization of the Compressive Behaviour of an Al Foam by X-Ray Computerized Tomography

Al metal foams manufactured by the powder-method have been investigated. Compression tests were performed on the same sample at increasing deformation steps: at each stage the sample was observed by X-ray computerized tomography. A geometric evaluation of porosity on many sections was performed by calculating, for each pore, its area, equivalent diameter, perimeter and circularity.

Prediction of Weld Metal Microstructure in Laser Beam Welded Clad Steel

In dissimilar welded joints, data for the phase composition of the fusion zone may be taken from the phase equilibrium diagram composed in the course of experimental observation of phases. Results are given in the article for test laser welding of low-carbon steel plates, clad with austenitic stainless steel, and specimens are studied demonstrating perfection of the welded section austenitic microstructure. This confirms the data about the reliability of martensite-austenite boundaries studied by D. T. Kotecki on the example of chromiumnickel deposits prepared by submerged arc welding on carbon steel plates. Welds are studied by optical and scanning electron microscopy, and microhardness is determined by the Vickers method. The content of the main substitution alloying elements is calculated by means of energy-dispersion spectroscopy. The nitrogen content is determined using a hot gas extraction method and carbon is determined proceeding from the chemical composition of the deposited and base materials. It is established that the chromium and nickel content in points of the welded section with an entirely austenitic microstructure is specified by coordinates Creq and Nieq in accordance with the austenite-martensite boundary proposed by Kotecki. Therefore, the results obtained confirm the possibility of predicting welded section microstructure from the position of this boundary, even in the case of joints welded with a laser beam with moderate solidification and cooling rates.