Papers by Author: E.P.R. Lima

Abstract: The use of pressed and sintered aluminum, obtained by the powder metallurgy route, to produce large quantities of near-net-shaped components is increasing rapidly in the automobile industry. The production of lightweight pieces of Al by powder metallurgy has attracted increasing attention due to its unique properties. Sintering helps develop mechanical strength and other properties in commercial alloys obtained by powder metallurgy. Sintering of Al can be achieved only upon formation of a liquid phase capable of destroying the extremely stable oxide layer on the surface of the Al particles. The aim of this investigation was to analyze the effect of compaction pressure on sintering of atomized ASTM 2124 type alloy. Powder characterization was carried out using scanning electron microscopy (SEM). The specimens were axially compacted at pressures of 500, 600 and 700 MPa. Differential scanning calorimetry (DSC) was carried out to determine the sintering temperature of the alloy powder. The specimens were sintered at 570° C. Characterization of the sintered material consisted of density measurements and optical as well as SEM examinations. Nevertheless, even the low recycling cost of Al , what increases its useful time and stabilizes its value, the large amount of energy required to obtain it reduce its application.

Abstract: The purpose of this study is to evaluate the effect of the stages and tempering temperatures in the microstructure, tenacity and hardness of the vacuum sintered high speed steel AISI T15. The material was uniaxial pressing at 700 MPa and sintered in a vacuum furnace at 1275°C. After that, different samples of the materials were submitted to the annealing treatment at 870°C, quenching at 1235°C and tempering (single, double and triple) at 540, 550 and 560°C. Concluded the treatments, Rockwell C measurements of hardness were accomplished and, to evaluate the toughness of the material, TRS (Transverse Rupture Strength) tests were done. Later on, the materials were submitted to the metallographic preparation for microstructure analysis in optical microscopy, SEM, EDX and X-ray diffraction. Finally, each property analyzed was evaluated and correlated with the different tempering stages and temperatures accomplished.