Alicia Esther Ares

Corrosion Resistance of Directionally Solidified Casting Zinc-Aluminum Matrix

Generally solidification leads to two types of grain morphologies: columnar and equiaxed. The origin of each one has been the subject of numerous theoretical and experimental researches in the field of metallurgy for many years. Columnar grains often grow from near the mold surface, where the thermal gradients are high, and the growth is preferentially oriented in a direction close to the heat flux. When the gradients are reduced near the center of the casting, equiaxed grains grow in all space directions leading to a material with more isotropic macroscopic mechanical properties and a more homogeneous composition field than with columnar structure. Depending on the application, one type of grain is preferred and thus favoured, e.g. equiaxed grains in car engines and columnar grains in turbine blades as reported by Reinhart et al, 2005 and McFadden et al., 2009.

Macroestructuras de solidificación versus parámetros térmicos y electroquímicos en aleaciones zinc-aluminio (za)

Los materiales bimetalicos se fabrican por una diversidad de razones, entre ellas podemos mencionar el reemplazar aleaciones costosas, mejorar el aspecto superficial, obtener mayor resistencia mecanica, resistencia al desgaste o a la corrosion. La presente investigacion se realiza en aleaciones zinc – aluminio (Zn-4%Al, Zn-16%Al y Zn-27%Al) en sus diferentes estructuras (columnar, equiaxial y con transicion, TCE), a fin de estudiar la vinculacion entre los parametros de solidificacion, estructurales y de resistencia a la corrosion de las mismas. Los resultados son fuertemente dependientes de la concentracion de aluminio en la aleacion, como asi tambien del tipo de estructura que las mismas presentan.

CORRELACIONES ENTRE PARÁMETROS TÉRMICOS, ESTRUCTURA Y MICRODUREZA EN ALEACIONES ZINC-ALUMINIO (ZA).

In the present research we investigate correlations between thermal parameters (cooling rate, velocity and position of solidification fronts, temperature gradients), type of structure (grain size, dendritic spacing) and microhardness in directional solidified samples of Zn-Al (ZA) alloys. We present correlations between cooling rate and the width of columnar grains, velocity of solidification fronts versus length of columnar grains, density of equiaxial grains versus temperature gradients, grain size, primary an secondary dendritic spacing and the variations in microhardness.