| Ultra fine Mg matrix composite powders can be used as interphase of Mg alloys and other metals or alloys to improve their properties, and can thus expand their application fields. The successful preparation of these powders could satisfy some needs of production and live, having potential economic and military significance.In this paper, ultrafine Mg powders were prepared by DC arc plasma in Ar, H2+Ar and CH4+Ar atmospheres. Ultrafine Mg-Mg2Si-Si composite powders were synthesized by DC arc plasma in SiH4+Ar and H2+SiH4+Ar atmospheres. Ultrafine Mg-Mg2Si-Si composite powders were produced by Mechanical alloying using Mg swarf and Si powders. The structure and morphology as well as the oxidation resistance of these ultrafine powders were analyzed by using XRD, TEM, SEM, electron diffraction, gas analysis and DSC-TG.The results show that the ultrafine powders were obtained by DC arc plasma evaporating pure Mg in Ar, H2+Ar, CH4+Ar atmospheres are single-phase Mg. The morphology of these powders exhibit sphere-like shape. The average diameters of the powders produced under the three conditions are about 156nm, 195nm and 181nm, and the specific surface area are 22.12m2/g, 17.70m2/g and 19.07m2/g, respectively oxidation resistance of ultrafine Mg powders obtained in CH4+Ar atmosphere is superior. For the ultrafine Mg-Mg2Si-Si composite powders obtained by DC arc plasma evaporating pure Mg in SiH4+Ar atmosphere, the contents of Mg2Si and Si in powders increase with increasing content of SiH4.The morphology of the powders present polyhedral or sphere-like shape, for example, the Mg2Si is polyhedral, and Mg or Si is approximately spheric. The powder size ranges from 20 to 200nm. Concerning the the ultrafine Mg-Mg2Si-Si composite powders obtained by DC arc plasma evaporating pure Mg in H2-+SiH4+Ar, with increase in the content of H2 ,the content of Mg in powders increases, but the contents of Mg2Si and Si decrease, and the average size of powders increase as well. Oxidation resistance of ultrafine composite powders is improved with an increase in the content of Mg2Si. Moreover, the ultrafine Mg-Mg2Si-Si composite powders were prepared by Mechanical alloying. It was found that the content of Mg2Si and impurity Fe in the powders increase with the increasing of the milling time and ball-to-powder weight ratio, but the contents of Mg and Si decrease. The size range of ultrafine powders are 50-800nm and 30-200nm for milling times of 15h and 30h, respectively. The morphology of ultrafine powders is irregular or approximately spheric, and the contents of oxygen are measured to be around 5.5wt% and 6.0wt%, respectively. |
