Fabrication of a novel Mg-RE(Nd,Ce) intermetallic compound coating by molten salt diffusion and its effect on corrosion resistance of magnesium alloys

A novel Mg-rare earth （Nd, Ce） coating containing intermetallic compound was fabricated on the surface of the AZ91D magnesium alloy by bathing the sample in a NaC1-KC1-LiC1-NdC13-CeC13 molten salt. The cross-sectional morphology, microstructure and phase composition of the coating were investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and energy dispersive spectroscopy （EDS）. The corrosion resistance was characterized by the potentiodynamic polariza- tion curves. The SEM observation indicated that a continuous and compact diffusion coating was obtained on the surface of SMATed AZ91D magnesium alloy and the XRD and TEM investigations revealed that the new phases were Al2Ce and A12Nd intermetallic. The potentiodynamic polarization curves showed that the Mg-RE coating improved the corrosion resistance of the AZ91D magnesium alloy, and the corrosion current density of the coated sample was about 1510 mA/cm2 lower than the uncoated sample.

High temperature calcium-magnesium-alumina-silicate(CMAS)corrosion behavior of directionally solidified Al_(2)O_(3)/YAG eutectic ceramic

1.Introduction Modern turbine engines can be substantially damaged when the airborne silicate-based particles(fly ash,desert sand,volcanic ash,runway debris,etc.)are ingested into jet engines at high temperatures(1150−1250℃)[1-4],leading to severe CaO-MgO-Al_(2)O_(3)-SiO_(2)(CMAS)corrosion during their service life.In order to extend the engine life,many efforts have been devoted to thermal barrier coatings(TBCs)and environmental barrier coatings(EBCs)to protect the substrate from corrosion by molten CMAS[5-7].To be specific,thermochemical and thermomechanical corrosion are the two main mechanisms of CMAS corrosion[8].The structure and composition of the coatings were changed due to the chemical reaction between the molten CMAS and coating,the detrimental phases were then precipitated[9,10].

Microstructure and Mechanical Property of the Large Cross-Sectioned Mg-Gd-Y-Zn-Zr Alloy Produced by Small Extrusion Ratio

In this work,the microstructure and mechanical properties of large cross-sectioned Mg-9Gd-3Y-1.2Zn-0.5Zr(VWZ931)samples produced by the small extrusion ratio has been investigated.The as-extruded VWZ931 sample with diameter of~30 mm can exhibit the high yield strength(YS)of 339 MPa,ultimate tensile strength(UTS)of 387 MPa and elongation of 8.2%,respectively.After peak-aged,the YS and UTS of the Mg samples were significantly increased to 435 MPa and 467 MPa.The small extrusion ratio leads to the low fraction of dynamic recrystallized(DRX)grains in VWZ931 sample,and the texture hardening effect can be fully utilized to achieve high strength.The combined effect of precipitation strengthening due to the long-period stacking ordered phases and theβ′phase,grain boundary strengthening due to the fine DRX grains,heterogeneous deformation-induced strengthening caused by bimodal microstructure,can together contribute to the high strength of present Mg alloy.The findings can shed light on designing other large-sized Mg wrought alloys with high mechanical performance.