EUROGUSS Talent Award New HPDC Alloys to Address Automotive Industry Requirements
In this ever-changing world, research and innovation is essential to address the different global challenges the world faces nowadays. The work presented here demonstrates that improvements in the mechanical properties of the alloy are achieved due to the incorporation of nanometric ceramic particles in the aluminum matrix.
Regarding global challenges such as the climate change, the efficiency in the use of resources or the sustainable transportation, it is essential for the European industry to develop innovative processes and products in order to overcome these societal and technological challenges. Traditional processes must be part of this evolution, and new technologies must also be applied to help them evolve towards a higher efficiency and productivity and improve quality in their products. The background of the project is the die casting process, which is being applied to the manufacturing of metallic components since the 19th century.
Aluminum Alloys in the Research Focus
In recent years, the automotive industry, considering the European requirements regarding the emission of polluting gases, has launched many projects with the aim of achieving new and better materials. Due to the low density and high mechanical properties, aluminum alloys are widely studied. An example of their applicability is the lightweighting of the vehicle that can be obtained by replacing parts made of steel by these new materials.
The incorporation of alloying elements or strengthening phases such as ceramic particles is one of the conventional ways to improve the mechanical properties of aluminum alloys. The work done studied the metal matrix nano composites (MMNCs) obtained due to the incorporation of ceramic nanosized TiC particles. The importance of this MMNCs is further relevant in automotive and aerospace industries due to the isotropic properties the particles provide.
Due to its simplicity and profitability, stir casting method is one of the most used liquid routes to produce aluminum based MMNCs. In order to improve mechanical properties some questions must be considered. Firstly, reinforcement type, size and amount. Then, due to the stirring process that is applied, other factors as stirring velocity, temperature or stirrer diameter must also be controlled.
The work shows the procedure used to obtain MMNCs, mechanical properties and the micrographs of pure aluminum samples in which the nano sized particles introduction is demonstrated.
During the project, the stir casting fabrication route was used in a semisolid state, through which the nanometric ceramic particles were introduced in the different aluminum alloys. In order to minimize the humidity of the nanoparticles, they have been preheated, for one hour, at 100° C. 2-3 kg of aluminum alloys have been used for each casting. Once the material is melted, the stirrer is introduced. The rotation speed is increased until a correct vortex is generated at a rotation speed of between 260-480 rpm. Then, nanoparticles are introduced. After introducing all the nanoparticles, the temperature of the melt is reduced to 630° C and the stirring is maintained for 15 minutes in order to perform a correct and homogeneous agitation. Finally, the temperature of the melt is increased to 720° C and the material is cast.
Enormous Improvement in Tensile Strength
Among all the materials studied, the incorporation of 0.1-0.5wt.% of nano TiC to an Al-Si7Mg0.3 alloy has shown the best performance with a 30 % of improvement in tensile strength. This benefit has been achieved thanks to the combination of mechanical stirring and ultrasonic application used to obtain a good dispersion of the added nanoparticles avoiding the agglomeration that usually hinders its positive effect.
In Table 1, mechanical properties of the base alloy in comparison with the obtained Al-Si7Mg0.3 sample properties are shown.The incorporation and structure of TiC particles after solidification is shown in Figure 1. The TEM micrograph is complemented with diffractograms in which the evaluation of pure aluminum and particles zones are evaluated.
Successful Fabrications of Al-TiC MMNCs
In the present research Al-TiC MMNCs were successfully fabricated and the following results were obtained:
- Mechanical properties improvement due to the nanoparticles (0.1-0.5wt.%) introduced.
- A good distribution of particles has been verified with TEM micrographs.
It is worth highlighting that no agglomerations were found.