New Process to Fabricate Magnesium Composites Using SiO<SUB>2</SUB> Glass Scraps

Abstract

To realize the lightweight effects by materials technology, a new process for fabricating high-performance magnesium composites via a solid-state reaction by using high purity SiO 2 glass scraps has been established. From a viewpoint of the microstructures control of the composites, the core technologies to improve the physical and mechanical properties are; a solid-state synthesis of Mg 2 Si and MgO particles by the deoxidization of SiO 2 glass by magnesium, and a refinement of both their dispersoids and the magnesium matrix grains by the RPW process. For example, when using the elemental AZ31 magnesium alloy and 2 mass% SiO 2 glass powder mixture as starting raw materials, the hot extruded composite including Mg 2 Si and MgO shows 363 MPa of the ultimate tensile strength. The addition of only 2 mass% SiO 2 powder also causes the remarkable improvement of the corrosion resistance because of the uniform distribution of refined Mg 2 Si not only at the particle boundary but also inside the grains. This process is quite safety and environmentally benign compared to the conventional re-melting process, because of utilizing course magnesium raw powder and no use of SF 6 toxic gas. It also shows a possibility to employ SiO 2 glass scraps as starting raw materials to fabricate magnesium alloys.

Biocompatible silica-based magnesium composites

“…Ben-Hamu et al found improved corrosion behavior of wrought Mg-Zn-Mn alloy with the presence of polygonal shape Mg2Si intermetallics [31,32]. Also, as reported by Kondoh et al the corrosion resistance of Mg2Si is better than that of stainless steels [28]. This conclusion was arrived based on salt spray tests according to JIS Z 2731 standard conducted on intermetallic bulk Mg2Si and conventional 304 stainless steel.…”

“…Sun et al studied the synthesis kinetics during the formation of Mg-Mg2Si composite and concluded that at temperatures below 580 o C, the elemental powders did not react completely to form Mg2Si [27]. In-house scraps of the wrought optical silica glass fiber were milled with AZ31 by Kondoh et al to fabricate composites by consolidation, heating and hot-extrusion [28]. However, they couldn't be used for bio-medical applications as they did contain lot of impurities as they were manufactured from scrap materials.…”

Thermo-Mechanical Treatment of Glass-Balloon-Dispersed Metal Matrix Composite

“…However, they showed the starting temperature of the exothermic at 730 K (Kondoh & Luagnvaranaunt, 2003c Figure 15 summarized the estimated volume fractions of crystalline phases formed by isothermal heating, which were calculated from the integrated intensity of peaks in XRD profiles. As the heating time increased, the oxidation of magnesium was accelerated as well as deoxidization of SiO 2 .…”

“…Since magnesium is the lightest metal in the structural materials, magnesium alloys also have great potential for applications in automotive and aerospace industries. Furthermore, solid-state recycling processes of magnesium alloy chips and/or fragments such as hot extrusion, mechanical alloying, equal channel angular extrusion (ECAE) and cyclically repeated plastic working (RPW) have been developed (Mabuchi et al, 1995;Clark et al, 1997;Kondoh et al, 2003aKondoh et al, , 2003bKondoh & Luagnvaranaunt, 2003c). The recycled materials show superior mechanical properties such as high strength and high strain-rate super-plasticity.…”

“…The recycled materials show superior mechanical properties such as high strength and high strain-rate super-plasticity. Kondoh et al (Kondoh & Luagnvaranaunt, 2003c) has established a process to fabricate high performance magnesium composite, in which Mg 2 Si and MgO particles were synthesized due to deoxidization of SiO 2 glass by magnesium, and a refinement of both those dispersoids and magnesium matrix grains was achieved during RPW. Under only 2 mass% SiO 2 addition in AZ31 alloy, the Mg 2 Si compound was employed as a reinforcement of the composite, because of its high hardness, high Young's modulus and superior corrosion resistance.…”