Study of alloys modification by nanomaterials

In last years, improvement of metals mechanical properties and performance comes to be one of the main challenges in materials science and particularly in metallurgical manufacturing. Generally, an alloying process is traditionally applied to reach metals enhanced properties and performance. Recently, nanotechnology approach is also applied, usually to produce composite materials with improved performance. This work, however, describes a different technique, where different nanoparticles areused as modifiers in metal casting process. The influence of these nanomaterials was investigated on a hypoeutectic casting aluminum alloy and on pure copper. Microstructural evaluation of modified Al alloy illustrated that a coarse Al grains were refined. Tensile strength tests revealed that Al ductility improved while the strength remained unchanged. Particularly, results pointed that addition of up to 0.1 wt. % of ceramic nanoparticles enhanced metals elongation at fracture by 20 – 60 %, depending on the mold location. Strengthening mechanism, which took place in the process, was evaluated by applying a high resolution transmission electron microscopy (HR-TEM) studies. HR-TEM investigations, jointly with mechanical properties test results, led to hypothesis that a grain-size strengthening mechanism works in the process. In this mechanism metal strengthening occurs due to a high concentration of grain boundaries which are serving as dislocation movement blockers. Results obtained on copper modification showed the improvement of metal strength simultaneously with its elongation at fracture. This behavior was obtained after addition of multi walled carbon nanotubes (MWCNT) and TiN nanoparticles up to 0.1 wt. %. Further application of the described approach can lead to its implementation into foundry industry turning it to more economically beneficial.