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RESUMEN:Este trabajo presenta una nueva metodología experimental y numérica para pronosticar la dureza de las aleaciones Al-Cu-Zn, tanto en estado de colada como solubilizadas y templadas, cuyas composiciones químicas se encuentren dentro de dos líneas limítrofes, representadas por dos ecuaciones. De cada una de las líneas limítrofes se seleccionaron ocho composiciones diferentes que se caracterizaron por metalografía óptica, microscopía electrónica de barrido, difracción de rayos X y dureza. Las fases en equilibrio a diferentes temperaturas se obtuvieron por medio del programa Thermo-Calc. De la caracterización microestructural y análisis de regresión se obtuvieron los diferentes cambios de fase y dos ecuaciones de dureza. Al combinar las ecuaciones de dureza con las ecuaciones limítrofes se puede deducir la dureza de cualquier aleación con composición química dentro de esta zona. Para comprobar la exactitud de este método, se pronosticó la dureza de aleaciones a partir de los datos de algunos artículos de otros investigadores; las durezas estimadas presentaron tan solo un error menor o igual al 7%. ABSTRACT: Prediction of hardness for Al-Cu-Zn alloys in as-cast and quenching conditions.This work presents a new experimental and numerical methodology in order to predict the hardness in the as-cast, and solution treated and quenched Al-Cu-Zn alloys. Chemical composition of alloys is located inside two straight lines represented by two equations. Eight different compositions were selected from each line. All the alloys were characterized for light microscope, scanning electron microscope, X-ray diffraction and Rockwell B hardness test. The equilibrium phases were obtained at different temperatures by Thermo-Calc. The microstructure characterization and regression analysis enabled to determine the phase transformations and two equations of hardness assessment. The combination of hardness equations and composition line equations permitted to estimate the hardness of any alloy composition inside this zone. This was verified by calculating hardness with the information reported in other works, with an error lower than 7% in the estimated hardness.

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The precipitation characterization of Al-4 mass% Cu-0.3 mass% Mg alloy with additions of 0.5 and 2 mass% Ag during aging treatments was carried out by transmission electron microscopy (TEM) and microhardness measurements. TEM observation of aged samples showed that the phase is the dominant phase and it is in coexistence with the 0 phase. Additionally, the phase has the morphology of polygonal prism (almost hexagonal) with flat interfaces and a thin thickness. The variation of the cube of mean radius of precipitates, r 3 , followed a linear relationship, as predicted by the Lifshitz, Slyosov and Wagner (LSW) theory for diffusion-controlled coarsening in both alloys. The coarsening process of the phase was slower in the aged Al-4 mass% Cu-0.3 mass% Mg-2 mass% Ag alloy. The decrease in hardness seems to be related to the coarsening of the phase and the loss of coherency.