The effects of minor Al and Ce on the microstructures, room-temperature and high-temperature mechanical properties of as-cast Mg-6Zn magnesium alloys were investigated. With the Al addition into Mg-6Zn alloy, the coarse eutectic Mg51Zn20phases were refined and distributed discontinuously. After adding 0.5wt.% Ce into Mg-6Zn-1Al alloy, a new needle-like Al2CeZn2phase was observed. Meanwhile, the volume fraction of Mg51Zn20phase decreased and the semi-continuous Mg51Zn20phase became discontinuous globular morphology. It has been observed that the addition of Ce element coarsens the grains, and 1wt.% Al addition enhanced the yield strength and ultimate strength from 86.35MPa, 229MPa to 90.7MPa, 238MPa, respectively. Moreover, the Ce addition can significantly increase the high-temperature mechanical properties of cast Mg-6Zn-1Al alloy.
KEYWORDSTwo 1,4-dihydro-Hantzsch pyridine derivatives were synthesized by three steps. In the condensation step, the reaction time can be shortened to 1.5 h through using H2SO4-acetic anhydride system as a catalyst rather than the acetic acid-piperidine systemin the cyclization step, the reaction time was shortened from 20 h in ethanol to 15 h in polar aprotic solvent, and the yield of two products also was increased from 43.3% and 39.7% in traditional solvent to 93.2% and 90.1% in polar aprotic solvent.Unsymmetrical 1, 4-dihydro-Hantzsch pyridine Condensation Catalyst Cyclization Polar aprotic solvent
The influence of trace strontium (Sr) addition on the microstructure and mechanical properties of Mg-8Al-1Nd-0.5Zn was investigated with OM, SEM, and XRD etc. The results show that the lamellar eutectics and divorcedβ-Mg17Al12were reduced or refined with trace Sr addition. Among the as-cast Mg-8Al-1Nd-0.5Zn-xSr alloys, the Mg-8Al-1Nd-0.5Zn-0.05Sr alloy exhibited the best mechanical properties in which the tensile strength, the yield strength reached to 244.9 MPa and 111.7 MPa respectively. In addition, with the increase of Sr addition, the ductility was improved and it was observed that the number of cleavage steps and secondary cracks decreased on the fracture surfaces of tensile samples. It was also observed that the fractures occurred in the coarseβ-Mg17Al12phase instead of the Mg/Mg17Al12interface or Al11Nd3phase.
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