Both Mg-1Mn-3.5Y and Mg-1Mn-1Y-2.5Nd alloys(mass fraction,%)were extruded at 380℃.Most of the(10 10) crystal planes in the Mg-1Mn-3.5Y alloy are parallel to the normal direction,while most of the(10 11)crystal planes in the Mg-1Mn-1Y-2.5Nd alloy are parallel to the normal direction.The tensile tests at room temperature,100℃ and 200℃ show that the Mg-1Mn-3.5Y alloy exhibits higher yield strength,but lower elongation to failure as compared with the Mg-1Mn-1Y-2.5Nd alloy. These differences in the tensile mechanical properties between the two alloys are mainly attributed to their different texture types and amount and distribution of the Mg24Y5 precipitates.The serration flow behavior is observed in the Mg-1Mn-1Y-2.5Nd alloy at 200℃,but does not occur in the Mg-1Mn-3.5Y alloy.The Mg-1Mn-3.5Y alloy shows the cleavage fracture mode,while the Mg-1Mn-1Y-2.5Nd alloy exhibits the dimple fracture mode.
The electroless Ni-P/Ni-W-P duplex coatings were deposited directly on AZ91D magnesium alloy by an acid-sulfate nickel bath.Nickel sulphate and sodium tungstate were used as metal ion sources and sodium hypophosphite was used as reducing agent.The coating was characterized for its structure,morphologies,microhardness and corrosion properties.The presence of dense and coarse nodules in the duplex coatings was observed by SEM and EDS.Tungsten content in Ni-P/Ni-W-P alloy is about 0.65%(mass fraction) and the phosphorus content is 8.18%(mass fraction).The microhardness of the coatings is 622 VHN.The coating shows good adhesion to the substrate.The results of electrochemical analysis,the porosity and the immersion test show that Ni-P/Ni-W-P duplex coatings possess noble anticorrosion properties to protect the AZ91D magnesium alloy.
The influence of preparation methods on the photoluminescence properties of ZnO film was studied.Two methods were applied to fabricate ZnO films in a conventional pulsed laser deposition apparatus.One is high temperature(500-700 ℃)oxidation of the metallic zinc film that is obtained by pulsed laser deposition.The other is pulse laser ablation of Zn target in oxygen atmosphere at low temperature(100-250 ℃).The photoluminescence property was detected by PL spectrum.The room temperature PL spectra of the ZnO films obtained by oxidation method show single violet luminescence emission centered at 424 nm(or 2.90 eV)without any accompanied deep-level emission and UV emission.The violet emission is attributed to interstitial zinc in the films.Nanostructure ZnO film with c-axis(002)orientation is obtained by pulsed laser deposition.The ZnO film deposited at 200 ℃ shows single strong ultraviolet emission.The excellent UV emission is attributed to the good crystalline quality of the film and low intrinsic defects at such low temperature.
