Abstract
A new class of magnesium alloys has been developed by dissolving large amounts of oxygen atoms into a magnesium lattice (Mg-O alloys). The oxygen atoms are supplied by decomposing titanium dioxide nanoparticles in a magnesium melt at 720 °C; the titanium is then completely separated out from the magnesium melt after solidification. The dissolved oxygen atoms are located at the octahedral sites of magnesium, which expand the magnesium lattice. These alloys possess ionic and metallic bonding characteristics, providing outstanding mechanical and functional properties. A Mg-O-Al casting alloy made in this fashion shows superior mechanical performance, chemical resistance to corrosion, and thermal conductivity. Furthermore, a similar Mg-O-Zn wrought alloy shows high elongation to failure (>50%) at room temperature, because the alloy plastically deforms with only multiple slips in the sub-micrometer grains (<300 nm) surrounding the larger grains (~15 μm). The metal/non-metal interstitial alloys are expected to open a new paradigm in commercial alloy design.
Highlights
One of the most interesting recent findings in the field of nanotechnology is the observation that nanoscale ceramic particles with extremely high surface energy can be decomposed in a metal melt, at a temperature much lower than their normal melting points[1]
We propose a new alloying method that uses oxygen atoms in Mg metal
The alloy was held at this temperature for 30 min, and the liquid material was slowly poured into a preheated rectangular steel mold (10 mm thickness)
Summary
The Mg-O alloy was fabricated using a gravity casting method. To evaluate the amount of oxygen atoms in the Mg-O alloy and pure Mg, the materials were examined using XPS (Thermo VG) with a monochromatic Al Kα source. Uniaxial tension and compression tests were carried out for the Mg-O alloy and pure Mg under a constant cross head speed with an initial strain rate of 1 × 10−4 s−1. The thermal conductivity was determined by multiplying thermal diffusivity by the specific heat and density. The thermal diffusivity was measured by means of the laser flash technique (LFA447, NETZSCH, Germany), the specific heat was measured by differential scanning calorimeter (DSC, DSC8000, Perkin Elmer, USA), and the density of specimens was measured by Pycnometer (Ultrapycnometer 1000, Quantachrome Co. Ltd, USA)
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