Density Of Magnesium Research Articles

Density of magnesium and magnesium-lithium alloys in solid and liquid states

Abstract New experimental data are presented on the density and thermal expansion of solid and liquid magnesium and ultralight magnesium–lithium alloys containing 23.03 and 30.02 at.% Li, respectively. The measurements were performed using the dilatometer method and the gamma-ray attenuation technique in the temperature range from 145 to 1244 K for magnesium and from 293 to ∼1000 K for the alloys. The density changes during the solid−liquid phase transition were directly measured for Mg and the Mg70Li30 alloy. The temperature dependences and reference tables of the investigated volumetric properties were developed. A comparison of the obtained results with literature data was made. The study showed that the eutectic composition in the magnesium− lithium system differs from 23 at.% Li. The concentration dependence of molar volume of the magnesium−lithium liquid system was found to be almost linear in the interval of 0−30 at.% Li and deviated noticeably from the corresponding dependence for an ideal mixture.

Processing of Closed-Cell Magnesium Foams

Lightweight metallic foams are an attractive material having excellent energy absorption and acoustic damping. The density of magnesium is the smallest among structural metallic materials, and is about two third of the density of aluminum. It is, however, difficult to produce magnesium foams by conventional process because of their chemical activity. This paper provides a novel manufacturing process of magnesium foams. Accumulative diffusion-bonding process can produce a magnesium matrix composite (preform) containing titanium hydride (TiH2) particles as a blowing agent. Foaming tests of three magnesium alloys, AZ31, AZ91 and ZA146, revealed that low solidus temperature is effective to produce fine cell morphology. Chemical composition is significantly important to optimize the cell morphology of magnesium foams.

The effect of atmosphere on the creep deformation of a particle reinforced aluminum alloy matrix composites

Creep behavior of the 6061 aluminum alloy matrix composite reinforced by 10 vol.% of alumina particles has been investigated at temperatures from 573 to 773 K in air and Ar atmospheres. Creep curves, stress dependence of the minimum creep rate, microstructures after creep deformation and the effect of the atmospheres on the creep behavior were examined. Deformation around grain boundaries was estimated by measuring the offset of marking lines across grain boundaries. Creep curves were dominated generally by tertiary creep in air and Ar at every temperature except in extremely low stress range at 773 K, where primary creep dominated. Large primary creep strain following an initial inverse type of transient creep was observed in air in the low stress range at 773 K. The effect of atmosphere was prominent only in the primary creep stage under extremely low stresses at high temperature. In the stage, large decrease in density and large deformation around grain boundaries with creep deformation in air were observed. Many voids and cracks were observed on the surface of the specimen crept in low stress range at 773 K in air. Filament like structures, which were seen to generate at particle-matrix interfaces or grain boundaries, were often observed on the fracture surfaces under the condition. Extremely high density of magnesium and oxygen was detected at the filament like structure by energy-dispersive X-ray spectrometry. The effects of the oxidation and the formation of the filament like structure on the creep behavior are discussed.

Superplasticity of a AIN/Mg-5wt%Al alloy composite made by a vortex method

Magnesium (Mg) matrix composites has a great potential to apply to automobile, aerospace industries since the density of magnesium is low as compared with other metal alloys and the composite is expected to achieve excellent mechanical, physical and thermal properties. High Strain Rate Superplasticity (HSRS) is expected to offer the efficiently near-net shape forming method for magnesium matrix composites, since HSRS materials usually exhibit an elongation of 250--600% at a high strain rate of about 0.1--10s{sup {minus}1}. The purpose of this study is to reveal the HSRS in a AlN particulate reinforced Mg-5wt%Al alloy composite fabricated by a vortex method. In addition, the superplastic deformation mechanism of the Mg matrix composite will be discussed.