Chemical composition modification of casting aluminium alloys for engine applications

Graziani, Alessandro (2016) Chemical composition modification of casting aluminium alloys for engine applications. [Laurea magistrale], Università di Bologna, Corso di Studio in Chimica industriale [LM-DM270], Documento ad accesso riservato.
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Abstract

The research activities were focused on evaluating the effect of Mo addition to mechanical properties and microstructure of A354 aluminium casting alloy. Samples, with increasing amount of Mo, were produced and heat treated. After heat treatment and exposition to high temperatures samples underwent microstructural and chemical analyses, hardness and tensile tests. The collected data led to the optimization of both casting parameters, for obtaining a homogeneous Mo distribution in the alloy, and heat treatment parameters, allowing the formation of Mo based strengthening precipitates stable at high temperature. Microstructural and chemical analyses highlighted how Mo addition in percentage superior to 0.1% wt. can modify the silicon eutectic morphology and hinder the formation of iron based β intermetallics. High temperature exposure curves, instead, showed that after long exposition hardness is slightly influenced by heat treatment while the effect of Mo addition superior to 0,3% is negligible. Tensile tests confirmed that the addition of 0.3%wt Mo induces an increase of about 10% of ultimate tensile strength after high temperature exposition (250°C for 100h) while heat treatments have slight influence on mechanical behaviour. These results could be exploited for developing innovative heat treatment sequence able to reduce residual stresses in castings produced with A354 modified with Mo.

Abstract
Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Graziani, Alessandro
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Parole chiave
casting aluminium alloys molybdenum heat treatment mechanical properties microstructure high temperature exposition
Data di discussione della Tesi
23 Marzo 2016
URI

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