Mg-12 Li, Mg-12 Li-3（Al-Si）, Mg-12 Li-7（Al-Si） and Mg-12 Li-9（Al-Si） alloys（all in wt%） were fabricated by high frequency vacuum induction melting in a water cooled copper crucible. After subsequently hotrolling and annealing, their microstructure and mechanical properties were investigated. Experimental results show that mechanical properties of Mg-12 Li alloy were significantly improved by the addition of Al-Si eutectic alloy. Mg-12 Li-7（Al-Si） alloy shows the highest strength of 196 MPa of the investigated alloys, which is about 1.8 times of the strength of Mg-12 Li alloy, and maintains high elongation of 27%.The improved mechanical property with addition of Al and Si in the eutectic proportion into Mg-12 Li alloy was attributed to the solution strengthening effect of A1 and precipitation hardening effect from AlLi and Mg_2 Si precipitates.
Zilong ZhaoXuegang XingJinyu MaLiping BianWei LiangYide Wang
To improve the comprehensive mechanical properties of Mg-15AI magnesium alloy, different amounts （from 0 to 4.0wt.%） of Nd were added to the alloy and six Mg-15AI-xNd alloys were prepared by metal mould casting. The effect of Nd content on microstructure of the alloys was investigated by means of OM, SEM, EDS, TEM, and XRD. The tensile properties were tested at room temperature （RT） and high temperature （473 K）. The results indicate that the primary a-Mg dendrite is significantly refined with the addition of Nd. The best refinement is reached at 1.0wt.% Nd content and the average dendrite arm spacing decreases from 80- 100 pm （without Nd addition） to -20 pm. A further increase in Nd content leads to the coarsening of the primary a-Mg dendrite. The addition of Nd improves the tensile properties of Mg-15AI both at RT and 473 K. The Mg-15AI alloy containing 1.0wt.% Nd exhibits the best tensile properties. Compared with the alloy without Nd, the yield and ultimate tensile strength of the Mg-15AI-1.0Nd alloy at RT increase from 132.3 to 148.6 MPa and 152.3 to 189.6 MPa, increase by 12.3% and 24.5%, respectively; and the elongation at RT increases from 0.05 % to 1.24%. The yield and tensile strength of the alloy at 473 K increase from 97.9 to 115.3 MPa and 121.6 to 140.1 MPa, increase by 15.2% and 20%, respectively. Further increment of Nd content to 1.5wt.% degrades the tensile properties, which is ascribed to grain coarsening and growth of the AI-Nd phase.
Copper oxide thin films were prepared by a direct-current magnetron sputtering method followed by a thermal annealing treatment at 100-500 ℃. The obtained films were characterized by X-ray diffraction, UV-vis absorption spectroscopy, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. With the increase of the annealing temperature, it was found that the films transformed sequentially from amorphous to single-phase Cu （100℃）, mixed-phase of Cu and Cu2O （150 ℃）, single-phase Cu2O （200 ℃）, then to mixed-phase of Cu2O and CuO （300 ℃）, and finally to single-phase CuO （400 - 500 ℃）. Further analyses indicated that the Cu/Cu2O thin films and the Cu：O thin films presented no further oxidation even on the surface in air atmosphere. Additionally, the visible-light photocatalytic behavior of the copper oxide thin films on the degradation of methylene blue （MB） was also investigated, indicating that the films with pure Cu2O phase or Cu/Cu2O mixed phases have excellent photocatalytic efficiencies.
The as-cast pure magnesium(Mg), with a purity of 99.99%, was hot-extruded at 300 ℃ to prepare a Mg bar with a diameter of 8 mm. The microstructure and mechanical properties of the sample before and after extrusion were investigated. The results show that the as-extruded microstructure is obviously refined with a large number of subgrains rather than equiaxed grains. A great number of(102) tensile twins can be observed significantly in the microstructure at the temperature. Mechanical properties including yield strength(YS) and ultimate tensile strength(UTS) increase greatly but uniform elongation(UE) decreases slightly as a result of work hardening.
