Papers by Author: Mário J.G. Santos

Abstract: The Direct Metal Laser Sintering (DMLS) technology uses a mixture of metal powders with different melting points to build objects layer by layer, directly from the geometric digitalised information. This process allows the manufacturing of prototype and production tools. In this study, the M3/2 high speed steel powder blended with 20 wt.% Cu3P and 0.25 wt.% graphite was laser-sintered, using two scan speeds (100 and 200 mm/s), keeping constant both hatching (0.30mm between two consecutive lines) and laser power (180W). The powder was spread in uniform layers of about 20m over a steel plate (100x60x6mm). The laser beam scanned small areas (12x15mm) in a single direction (OX). The surface morphology of the laser-sintered material shows that all material melted, but for 200mm/s scan speed, strings are well defined. This is probably due to a lower level of energy supplied to the material. The microstructure of the sintered material was studied in the longitudinal and transverse sections, to evaluate the consolidation process and layer growth. The material showed porosity and cracks formed during the process.

Abstract: The aim of this work was to improve the joining between the fastening elements and the aluminium alloys foams. The research work was carried out on joining fastening elements into aluminium alloy foams during the foaming process, i.e., foaming around fastening elements. The foamable precursor material was produced by hot pressing the powder mixture of metal and a small fraction of the blowing agent. A steel mould containing a foamable precursor material and the fastening elements were heated to temperatures above the melting point of metallic matrix of foamable precursor material in order to obtain the final specimens. Each aluminium foam specimen (6061 and AlSi12) has 200x80x80mm and contains two fastening elements. The steel moulds design, the fastening elements geometry, the aluminium alloy composition, as well as the foaming parameters were studied in order to optimise the quality of the joints produced. The quality of the joints were determined by means of visual inspection and mechanical tests.