Compuestos de matriz metálica rica en Zn, con alto contenido de Al y componentes estructurales de compuestos intermetálicos de Cu -- Zn y Cu -- Al particulados

Abstract

The primary target of this work is to establish if it is feasible to elaborate, from powders, materials that have the composition of the Zn -- 22%wt Al eutectoid alloy, with different contents of Cu and whose structural characteristics allow defining them more appropriately like composite materials of metallic matrix and particulate structural components. The secondary targets are: determining by comparison if these materials are more resistant than their homologous alloys, processed by conventional casting and later homogenized; to establish the degrees of relative reinforcing, the minimum Cu content and minimal sintering time, used in this work, for which the structural components are formed, and the possible time for the formation of alloy with eutectoid composition as the matrix. It was begun with the briquette processing, by simple compaction and a load of 16 tons; the quantities of Cu used were 0.25, 0.5, 0.75, 1.0, 3, 5 and 7% of the weight of each sample. It was come with his sintering during three different times - 15, 75 and 210 minutes -- in an atmosphere of argon at 357$^\circ$C. Also, the homologous alloys were manufactured by casting and homogenized later during 100 hours at 360$^\circ$C. The characterization took place with the metallographic, microanalysis by EDS and X ray diffraction techniques, and tests of micro-hardness Vickers and hardness Rockwell B. It was managed to manufacture composite materials with structural components of CuZn$_{5}$, CuZn$_{2}$ or CuAl$_{2}$ intermetallic compounds, since the first 15 minutes of process and for all cooper contents used. The micro-mechanisms associated with the formation of these particles, allow deducing that the metallic matrices will not have totally the perlitic structure, not concerning the time of their sintering. The resistances to plastic deformation are greater than those from their homologous alloys. The maximum resistances are obtained in the materials with 0.5 and 3%wt Cu. The maximum degrees of reinforcing are reached with a 0, 25%wt cooper content, and between 3 and 5% in weight, with respective magnitudes of 556 and 280 in percentage units.