Abstract
In this work the microstructural changes that occurs during the solution and aging steps of heat treated of AlSi alloys, conformed in semi-solid state, were analysed. The study allowed developing a new T6 heat treatment, with solution times down to 30 min. With this new short heat treatment, the alloy showed better mechanical properties in comparison with the same alloy heat treated in standard conditions (solution times between 6 h and 8 h). This new heat treatment, carried out at 540 oC, allowed complete magnesium dissolution and, at the same time, minimizes the grain and eutectic silicon growth. Although this experimentation was carried out with A356 and A357 aluminum alloys, conformed by Sub-Liquidus-Casting process, these results may be applicable to components produced with other semi-solid technologies and with others AlSi hardenable alloys that form coherent magnesium precipitates. The characterization of samples was carried out by micrographic analysis, by hardness and ultramicrohardnes tests.
Highlights
In this work the microstructural changes that occurs during the solution and aging steps of heat treated of AlSi alloys, conformed in semi-solid state, were analysed
With this new short heat treatment, the alloy showed better mechanical properties in comparison with the same alloy heat treated in standard conditions. This new heat treatment, carried out at 540 oC, allowed complete magnesium dissolution and, at the same time, minimizes the grain and eutectic silicon growth. This experimentation was carried out with A356 and A357 aluminum alloys, conformed by Sub-Liquidus-Casting process, these results may be applicable to components produced with other semi-solid technologies and with others AlSi hardenable alloys that form coherent magnesium precipitates
Estas circunstancias pueden reducir notablemente los tiempos de puesta en solución de los tratamientos T6 cuando se aplican a componentes fabricados en estado semisólido
Summary
Las aleaciones AlSi son aleaciones de fundición ampliamente utilizadas en la industria de la automoción por sus buenas propiedades mecánicas específicas. A partir de estas aleaciones se pueden obtener componentes, por conformación en estado semisólido, con buen acabado superficial y prácticamente libres de porosidad. Los parámetros generalmente utilizados para tratamientos T6 son los propuestos por las normas ASTM B917 y ASTM B91: puesta en solución a la temperatura de 540 oC durante 6 h a 12 h (en la industria se realizan generalmente en 6 h) y un envejecimiento artificial a la temperatura de 155 oC, entre 3 h y 5 h. La estructura de estos productos es más homogénea y los precipitados intermetálicos que se encuentran en el entorno de los glóbulos de fase a, junto al microconstituyente eutéctico, son de menor tamaño. Estas circunstancias pueden reducir notablemente los tiempos de puesta en solución de los tratamientos T6 cuando se aplican a componentes fabricados en estado semisólido. El análisis químico de los compuestos intermetálicos se ha realizado por espectrometría de energía dispersiva de rayos X (EDS)
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