Abstract
This study presents a new concept of refining and enhancing the properties of cast aluminum alloys by adding nanoparticles. In this work, the effect of adding alumina (Al2O3), titanium dioxide (TiO2) and zirconia (ZrO2) nano-particles (40 nm) to the aluminum cast alloy A356 as a base metal matrix was investigated. Alumina, titanium dioxide and zirconia nano-powders were stirred in the A356 matrix with different fraction ratios ranging from (0%–5%) by weight at variable stirring speeds ranging from (270, 800, 1500, 2150 rpm) in both the semisolid (600 °C) and liquid (700 °C) state using a constant stirring time of one minute. The cast microstructure exhibited change of grains from dendritic to spherical shape with increasing stirring speed. The fracture surface showed the presence of nanoparticles at the interdendritic spacing of the fracture surface and was confirmed with EDX analysis of these particles. The results of the study showed that the mechanical properties (strength, elongation and hardness) for the nanoreinforced castings using Al2O3, TiO2 and ZrO2 were enhanced for the castings made in the semi-solid state (600 °C) with 2 weight% Al2O3 and 3 weight% TiO2 or ZrO2 at 1500 rpm stirring speed.
Highlights
Al-Si alloys are used for several automotive applications and various aerospace industries due to their outstanding properties such as high castability, abrasion resistance and excellent strength to weight ratio.The Al-Si alloys in particular are greatly known for their rapidly advancing activities in aircrafts, aerospace and automotive industries
The ultimate goal of the work is to discuss the options for producing nanocomposites via the casting route, in order to evaluate the options for using nanoparticles dispersion for the production of semi-solid cast A356 alloy with improved properties
The results show that the addition of 1 weight% nanoparticles did not produce a significant change in the wear resistance of the hypo-eutectic alloy A356, though there was a reduction in the friction coefficient
Summary
Al-Si alloys are used for several automotive applications and various aerospace industries due to their outstanding properties such as high castability, abrasion resistance and excellent strength to weight ratio.The Al-Si alloys in particular are greatly known for their rapidly advancing activities in aircrafts, aerospace and automotive industries. Though Na and Sr are used to achieve refinement of the eutectic silicon, a combined effect does not happen at the same time with P due to chemical incompatibility of phosphors with other modifying chemicals such as strontium and sodium. This has been explained [2] to result from the formation of strontium phosphide or sodium phosphide upon the addition of strontium or sodium to phosphorus pre-refined alloys. Other investigations have shown that adding rare earth elements would result in modification and refinement of the primary and eutectic silicon particles [5,6]
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