Precipitation Kinetics of an AlSi7cu3.5Mg0.1 Alloy with Zr and V Additions

"Nowadays, in order to fit environmental restrictions, automotive markets are demanding cast aluminum alloys working at high temperature (180–300°C). New generations of alloys are required for higher strength components in engine downsizing or start-stop systems which lead to higher loading and higher specific power and stretch current materials to their limits. Recently, transition metals, such as zirconium and vanadium, have been added as alloying elements into an AlSi7Cu3.5Mg0.1 alloy to improve physical, mechanical, thermodynamic properties with the aim of increasing service life of parts. In such alloys, the best mechanical properties are associated with the formation of precipitates through an optimum heat treatment sequence, including: solutionizing, quenching and artificial aging. This study is focused on the modified AlSi7Cu3.5Mg0.1 cast alloy with Mn, Zr and V additions for high temperature application. The characterization of the cast alloy in this study, firstly, helps to evaluate and understand its performance both chemically and structurally according to their physical state: as-cast or as-quenched. Comparison of precipitation kinetics between a binary Al-3.5%wt.Cu alloy and the AlSi7Cu3.5Mg0.1 (Mn, Zr, V) alloy has been characterized by differential scanning calorimetry, TEM observations and micro-hardness testing. The Kissinger analysis was applied to extract activation energies from non-isothermal DSC runs conducted at different stationary heating rates. The study focuses on the impact of the chemical composition such as Si content on the kinetics parameters.INTRODUCTION Pure metal Aluminum shows poor mechanical properties and its malleability is high, that is why alloying elements are added to the mixture before casting to improve physical, mechanical and thermodynamic properties (Javidani, 2015); such as Silicon (Si) for casting properties (castability, cold crack capability, wear resistance, shrinkage behavior), Magnesium (Mg) and Copper (Cu) to generate precipitation hardening systems. Aluminum hypoeutectic alloys (<12% Silicon) with Cu, Mg additions used in the automotive industry for manufacturing mechanical parts (Larouche & Javidani, 2014) are mostly subject, after casting, to precipitation hardening heat treatment (Mohamed & Samuel, 2012) according to specifications and associated standards. The best mechanical properties are associated with the formation of precipitates through an optimum heat treatment sequence, generally including: solutionizing, water quenching and artificial aging (Manente & Timelli, 2011). Hypoeutectic aluminum-copper alloy with amount of Cu around 1 to 4.5wt% is an elementary case for precipitation in heat treatable aluminum alloys. Researchers essentially focused their work on the full precipitation sequence of binary Al-Cu alloy during aging which is presented below."