Fabrication of nanosized Al 2 O 3 reinforced aluminum matrix composites by subtype multifrequency ultrasonic vibration
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Nanosized Al2O3 (Al2O3np) reinforced Al7075 composites were fabricated by specially made Al2O3np containing Mg powder and subtype multifrequency ultrasonic vibration. Compared to traditional techniques, Al2O3np was effectively dispersed in the matrix by the novel method. Microstructural studies showed that the addition of Al2O3np caused the grain refinement and that the resultant microstructures of composites depended on the dominant size and degree of Al2O3np clustering. The grain refinement could be mainly attributed to particle pushing mechanisms. Compared to the matrix alloy, the ultimate tensile and compressive strength of the as-cast composite with 1.5 wt% Al2O3np fabricated at 800 °C were increased by 59.6% and 42.6%, respectively. Transmission electron microscope analysis showed that high density dislocations and clear interfaces between particles and matrix were present in the grains, suggesting that the superior improvement of mechanical properties can be attributed to dislocation-type strengthening of matrix alloy and load transfer from matrix to hard nanoparticles.
I. INTRODUCTION
Aluminum alloy matrix composites reinforced with micrometer-sized ceramic particles are widely used for high performance applications such, as in military, aerospace, and automobile industries due to their improved physical and mechanical properties.1–3 And yet, the composites relate to hitting a wall at the applications since built of thermal stresses at the interface between larger particles and matrix can prematurely lead to de-bonding of the particle interface,4,5 which indicates that the improvement in the mechanical properties of composites is limited. Again, the ductility of the composites deteriorates significantly with the high particle concentration.6 In the recent years, some researches have studied the fabrication of the composites reinforced with nanosized particles. They found that the improvement in the mechanical properties of composites was considerable even with low content of particles. 7–10 Mechanical properties of composites such as strength and ductility may be significantly improved, simultaneously if nanosized particles are uniformly dispersed in the matrix. The particle reinforced composites which are fabricated via mechanical alloying with high energy milling, powder metallurgy, spray deposition, infiltration of metal alloy into a particle preform, etc., represent
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.198 J. Mater. Res., Vol. 30, No. 14, Jul 28, 2015
improved mechanical properties and homogeneous microstructures.11–15 For mechanical alloying, it normally involves mechanical mixing (e.g., ball milling) of metallic and ceramic particles for the fabrication of composites. During the ball milling, it is easily led to the sintering and oxidation of metallic particles. Meanwhile, the mixing of nanosized particles is lengthy, expensive, and energy consuming. With the other fabrication processes, they suffer from limitatio
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