Papers by Keyword: Magnesium Alloy

Abstract: The effect of Sr addition on microstructure evolution of Mg-6Zn-2Al-2Ca-xSr (x=0.5, 1, 2, 3）alloys were investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD) and optical microscope. The result show that Sr constitutional under cooling can significantly refined microstructure of alloys and formed rod-shaped Al4Sr phase in Mg-6Zn-2Al-2Ca alloys, while alloy microstructure turned to be coarse with further increase in Sr content. The addition of Sr slows down the precipitation power of Mg-6Zn-2Al-2Ca alloys and inhabits the β phase continuous precipitation.

Abstract: HIPIB irradiation into AZ31 magnesium alloy is performed at ion current density of 100-300 A/cm² with 1 shot. The surface morphologies and surface profiles of the irradiated AZ31 magnesium alloy samples are characterized by scanning electron microscopy (SEM) and profilometer, respectively. It is found that HIPIB irradiation leads to the formation of crater in local region of irradiated samples, and crater density increases with increasing ion current density. Both the surface roughness that reflects the vertical wave of surface profile and the mean spacing of surface profile irregularities that reflects the horizontal wave of surface profile increase as ion current density increases. These results are in agreement with the SEM observation on the irradiated surface.

Abstract: Mg_-1Mn_-0.6Ce_-xY (x=0, 1, 2 and 3, mass fraction, %) magnesium alloys were prepared by casting method. And the influences of yttrium on microstructure and mechanical properties of the Mg_-1Mn_-0.6Ce magnesium alloy were investigated. The results reveal that the addition of yttrium to the Mg_-1Mn_-0.6Ce alloy could reduce the grain size of the as-cast alloys and improve mechanical properties during the investigated temperature range. The Mg_-1Mn_-0.6Ce_-1Y alloy exhibits maximum ultimate strength, yield strength, elongation and the values are 152 MPa, 72 MPa and 13.4% and enhanced about 23.1%, 63.6% and 38.1% compared with those of Mg_-1Mn_-0.6Ce alloy at room temperature, respectively. The improvement of mechanical properties are attributed to the grain refinement and the precipitation strengthening generated by the Mg₁₂Ce phase particles and the fine Mg₂₄Y₅ precipitations.

Abstract: An attempt was made to produce organic sealed micro arc oxidation coatings on ZM5 magnesium alloy using two different kinds of organic solution which are acrylics and PTFE. The thickness, potentiodynamic polarization test, corrosion weight lost and morphologies of the coatings were investigated. The results indicate that PTFE sealed micro arc oxidation coatings has relatively dense and uniform surface to show the best anti-corrosion performance.

Abstract: An automatic high velocity arc spraying process was used to deposit a type of FeCrBSiMoNbW amorphous/nanocrystalline coating with substrate of AZ91 magnesium alloy. The microstructure of the coating was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDAX). The coating is about 250μm in thickness with low porosity and oxids. The results show that the microstructure of the coating can be classified into two regions, namely, a full amorphous phase region and homogeneous dispersion of α-Fe (Cr) nanocrystals with 30-80 nm in a residual amorphous region. Mechanical properties, such as nano-hardness, elastic modulus, were analyzed. The experimental results show that the coating has high nano-hardness and elastic modulus. The friction and wear experiments were operated on UMT-2 micro friction tester. The relative wear resistance of the FeCrBSiMoNbW coating is about 2 times higher than that of the conventional 3Cr13 coating under the same conditions. The main wear mechanism of the amorphous/nanocrystalline coating is the typical brittle spalling.

Abstract: A new technique has been developed by infiltration during casting process to AZ91D magnesium alloy part. Through a melting process a alloyed surface layer was formed on the surface of the part in casting process, and the surface layer helps improve the corrosion resistance. The macro morphology, thickness, microstructure and properties of the layer were analyzed by digital, scanning electron microscopy, spectroscopy and corrosion measurement system. The results show that a uniform and dense infiltration layer on the surface of AZ91D part was obtained. This technique can fundamentally change the physical and chemical properties of magnesium alloy parts. More importantly, it is low-cost, green and environmental protection.

Abstract: The brazing process of magnesium alloy AZ31 was studied, and the mechanical properties of the weld were examined, and the main factors were analyzed through brazing furnace tests in this work. Only with the protection of self-made brazing flux, a lap joint with the average shear strength of 30MPa could be obtained in an ordinary resistance furnace without inert gas protection, which is much better than that without flux in which the shear strength is lower than 10MPa.

Abstract: The effect of drawing speed and heating length on deformation behavior was investigated by numerical approach for AZ31 magnesium alloy tubes to realize high speed dieless drawing process. The length of deformation zone expands with increasing the feeding speed. The increase in heating length leads to expanding length of deformation zone. The mean strain rate increases with increasing the feeding speed firstly, and then rate of increase in the strain rate becomes gradual under condition of any length of heating band. Based on these results, a limiting reduction in area of 52.5% under higher speed and larger heating length conditions can be realized experimentally.

Abstract: Micro-arc oxidation coating on AZ91D magnesium alloy is prepared in a NaAlO2-NaOH-montmorillonite-acacia gum electrolyte solution with adaptive electric parameters. The morphologies, composition, phase component of the coatings are analyzed by SEM, EDS and XRD. And CHI600B electrochemistry workstation is employed to investigate the corrosion resistance of the coatings. The results show that the MAO coating has the relatively uniform in thickness. The coating is mainly composed of MgO and MgAl2O4 phases. It provides corrosion protection by acting as a barrier. The MAO coating enhances the corrosion resistance of the magnesium alloy AZ91D to some extent.

Abstract: Pure magnesium and AZ31B magnesium alloy were irradiated by a high current pulsed electron beam (HCPEB) device with pulse times 10, 15 and 20 respectively. The microstructure changes of the surface and modified layer after HCPEB treatment were investigated, and the evolution of temperature field during the electron beam modification process was numerically simulated based on experimental and theories. Numerical simulation analysis is close to experimental results and the special surface morphology arising from treatment is interpreted.