简介概要

SiC nanoparticles reinforced magnesium matrix composites fabricated by ultrasonic method

来源期刊:中国有色金属学报(英文版)2010年第z3期

论文作者:王朝辉 王旭东 赵宇昕 杜文博

文章页码:1029 - 1032

Key words:magnesium matrix composites; AZ91 alloy; SiC nanoparticles; ultrasonic method

Abstract: SiC nanoparticles reinforced magnesium matrix composites were fabricated by ultrasonic method. The AZ91 alloy and SiC nanoparticles with the average diameter of 50 nm were used as the matrix alloy and the reinforcement, respectively. The addition of nanoparticles was 0.1%, 0.3%, and 0.5% (mass fraction) of the composites. The results of microstructural evaluation and mechanical properties indicate that the nanoparticles can be dispersed into magnesium alloys efficiently and uniformly with the aid of ultrasonic vibration. As compared with the matrix alloys, the grains of composites were refined and the mechanical properties of composites were improved significantly. The SEM and DSC analyses show that the SiC nanoparticles can act as the heterogeneous nucleation of α-Mg. Also, the strengthening mechanism responsible for the composites reinforced with SiC nanoparticles was discussed.

基金信息:the National Basic Research Program of China



详情信息展示

Trans. Nonferrous Met. Soc. China 20(2010) s1029-s1032

 

SiC nanoparticles reinforced magnesium matrix composites fabricated by ultrasonic method

WANG Zhao-hui(王朝辉), WANG Xu-dong(王旭东), ZHAO Yu-xin(赵宇昕), DU Wen-bo(杜文博)

College of Materials Science and Engineering, Beijing University of Technology,

Beijing 100124, China

Received 13 May 2010; accepted 25 June 2010

Abstract: SiC nanoparticles reinforced magnesium matrix composites were fabricated by ultrasonic method. The AZ91 alloy and SiC nanoparticles with the average diameter of 50 nm were used as the matrix alloy and the reinforcement, respectively. The addition of nanoparticles was 0.1%, 0.3%, and 0.5% (mass fraction) of the composites. The results of microstructural evaluation and mechanical properties indicate that the nanoparticles can be dispersed into magnesium alloys efficiently and uniformly with the aid of ultrasonic vibration. As compared with the matrix alloys, the grains of composites were refined and the mechanical properties of composites were improved significantly. The SEM and DSC analyses show that the SiC nanoparticles can act as the heterogeneous nucleation of α-Mg. Also, the strengthening mechanism responsible for the composites reinforced with SiC nanoparticles was discussed.

Key words: magnesium matrix composites; AZ91 alloy; SiC nanoparticles; ultrasonic method

1 Introduction

Magnesium alloys are the lightest structural metallic materials, but the mechanical properties and creep resistant property of most common commercial magnesium alloys cannot meet the developing demands of the industries[1-5]. Hence, the magnesium matrix composites are attracted more attention because of their excellent properties, such as high specific modulus, high specific strength, low coefficient of thermal expansion and good wear resistance[6].

Recently, nano-sized ceramic particles, such as SiC, Al2O3, Y2O3 are used as reinforcement in magnesium matrix composites. The nanoparticles reinforced magnesium matrix composites show more excellent mechanical properties than those reinforced by micro-scale particles, but the key problem in the case of nano-sized particles is how to disperse them into the matrix alloys efficiently and uniformly. Among the efficient methods, there are ball-milling method[7-8], disintegrated melt deposition (DMD) method[9-10], ultrasonic dispersion method[11-12], semisolid process [13] and so on.

In the present work, AZ91 alloy and SiC nanoparticles were used as the matrix alloy and reinforcement, respectively. The reasons responsible for selecting SiC as reinforcement are due to its high hardness and strength and its heterogeneous nucleation effect in the molten magnesium alloys[6,14-15]. The composites were fabricated by ultrasonic method, the microstructure and mechanical properties of the composites were evaluated and the strengthening mechanism of the SiC nanoparticles was discussed.

2 Experimental

The commercial AZ91D magnesium alloys (8.94% Al, 0.70% Zn, 0.22% Mn, 0.02% Si, balance Mg) (mass fraction) were used as the matrix alloys. The beta-SiC particles with the average diameter of 50 nm were used as the reinforcing particles. The transmission electron micrograph (TEM) of the SiC nanoparticles is shown in Fig.1.

The clean and preheated magnesium ingots of about 600 g were put into an Al2O3 crucible. Then the magnesium alloy was heated to about 650 ?C in a resistance furnace. After the alloy was melted, the treated SiC nanoparticles were added into the melting magnesium alloy, and then the ultrasonic probe was dipped in the melt about 20 mm with the output power of 0.6 kW for about 30 min (the ultrasonic wave was 20.0 kHz with the maximum output of 2.0 kW). After the ultrasonic treating, the composites were cooled down to about 630 ?C and cast into the permanent mold preheated to 200 ?C. The whole experiments were carried out with the protection of 0.5%SF6+N2. The addition of SiC nanoparticles was 0.1%, 0.3% and 0.5% (mass fraction) of the composites, respectively. The contrastive samples without nanoparticles were also prepared with the same procedures.

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