Development and Characterization of Mg-SiC Nanocomposite Powders Synthesized by Mechanical Milling

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Magnesium powder in micron scale and various volume fractions of SiC particles with an average diameter of 50 nm were co-milled by a high energy planetary ball mill for up to 25 h to produce Mg-SiC nanocomposite powders. The milled Mg-SiC nanocomposite powders were characterized by scanning electron microscopy (SEM) and laser particle size analysis (PSA) to study morphological evolutions. Furthermore, XRD, TEM, EDAX and SEM analyses were performed to investigate the microstructure of the magnesium matrix and distribution of SiC-reinforcement. It was shown that with addition of and increase in SiC nanoparticle content, finer particles with narrower size distribution are obtained after mechanical milling. The morphology of these particles also became more equiaxed at shorter milling times. The microstructural observation revealed that the milling process ensured uniform distribution of SiC nanoparticles in the magnesium matrix even with a high volume fraction, up to 10 vol%

Effect of SiC nanoparticles on manufacturing process, microstructure and hardness of Mg-SiC nanocomposites produced by mechanical milling and hot extrusion

The production of fully dense Mg-SiC nanocomposites with a homogeneous distribution of SiC nanoparticles through powder metallurgy techniques is still a challenging issue. We propose to combine sintering and hot extrusion of mechanically milled composite powders to encompass the known difficulties of conventional processing. Here, we report on the effect of SiC nanoparticle content on the compressibility, microstructure and hardness of SiC-Mg nanocomposites during the different consolidation steps. Cold-isostatic pressing, sintering and indirect hot extrusion were used for compaction and consolidation. Near dense Mg-SiC nanocomposites with 1 and 10 vol% SiC nanoparticles were successfully produced with a homogeneous distribution of the nanoparticles. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy were used to characterise the microstructure of the powders and of the sintered and extruded Mg-SiC nanocomposites. Vickers microhardness tests were done to reveal the hardening effect after sintering and extrusion. The nanoparticles pin the grain boundaries and foster dynamic recrystallisation, so that a nanograined Mg matrix develops and is preserved even after the final consolidation step. The results further show a very good interface adherence between nanoparticles and matrix contributing to the high hardness of the nanocomposites