Materiales compuestos de matriz metálica rica en Zn con alto contenido de Al y componente estructural de ZnO

Abstract

The aims of this work were to elaborate composites of metallic matrix rich in Zn with high content of Al and different contents of particulate ZnO by the conventional technique of powders metallurgy; to establish initial times of theirs manufactures, structural changes, basic mechanical properties of integrants and microstructures, and basic phenomena happened during formation of this composites as a function of the process time and ZnO content. It was begun with preparation of Zn and Al powder mixes, in convenient proportions to form Zn -- 22%wt Al alloy, and powders quantities of ZnO that were 0.0%, 0.01%, 0.1%, 1% y 10% of the total weight of each mix. The mixes were after compacted with a load of 16 tons and acetone as lubricant. The sintering was made in steps of 15 minutes of duration at 357$^\circ$C. Before each sintering step, the samples were conventionally grinded, polished and etched. The obtained structures were photographed. Vickers micro-hardness and Rockwell G hardness were respectively measured in constituents and microstructures. The ZnO in proportions not higher than 0.1%wt causes that it is concentrated the compression on metallic powders. Which improves atomic species diffusion and, therefore, it accelerates the union among components, formation of solid solutions and the interest alloy, producing an initial reinforcement of the matrix that seems not to depend on the oxide quantity at short times of process. It is established an increase of integrants size and the formation of pearlite type substructure, which is characteristic of the homogenized Zn - 22% wt Al alloy, in a considerable proportion of the microstructures at longer process times. This causes a softening of the matrix and then it is evident the reinforcement caused by ZnO. The ZnO content above 0.1% wt. delays the alloy formation in matrix. The minimal time for elaboration of these materials is 75 minutes.