Resrarch On Long Period Stacking Ordered Enhanced Mg-Zn-Y-Mn-(Mo) Alloys

The Mg-Zn-Y family enhanced by long period stacking ordered structure(LPSO)apace became research hotspots in the academic circles and the industries due to their special microstructure and ideal mechanical properties.Because of the high price of rare earth Y,it becomes an vital research problem on how to obtain more LPSO phase under the same Y element content.In this paper,the Mg-Y-Zn-Mn alloys were selected as the based alloy and prepareddifferentMo-modifiedalloysbyconventionalcasting process.Quantitative analysis of the effect of Mo microalloying on microstructure,second phase and comprehensive performance in the based alloy.Under the optimal amount of Mo addition,the effect of solution treatment on the microstructure and properties of Mg-Y-Zn-Mn-(Mo)alloys was studied.Based on the suitable solution treatment method,we explored the impact of extrusion temperatures on the microstructure,corrosion resistance and mechanical properties of the Mo-modified alloy.The main results are described as follows:(1)Microstructure of the Mo-modified alloy refine,uniform and equiaxed;he 18R LPSO phase volume fraction was significantly increased and presented anisotropic distribution;The W phase exhibited coral-shape rather than fishbone-shape.Mg-Zn-Y-Mn alloy with the addition of 0.3wt%Mo acquired finest grains,the grain size is approximately 22μm and manifested more desirable properties with corrosion rate,ultimate tensile stress and evident elongation of 1.14mm/y,265MPa and 15%,respectively.(2)The spheroidization of network W phase and precipitation of lamellar14H LPSO phase occurred in as-heated alloys.The addition of Mo increased the W-phase spheroidization rate,promoted the formation of 14H LPSO phase and kept the 18R LPSO phase at a certain volume fraction.(3)Solution treatment further improved the comprehensive performance of the based alloy on the basis of Mo microalloying.The as-heated Mo-doped alloy possessed the good corrosion resistance and excellent mechanical properties,corrosion rate by weight loss test,corrosion potential and corrosion current density were 0.986mm/y,-1.413V and 38.49μA/cm~2,respectively.The tensile strength reached 270MPa,the elongation reached 23%.(4)Extrusion temperature has an effective effect on the corrosion resistance and mechanical properties of Mg-Y-Zn-Mn-Mo alloys.When extrusion temperature was 350℃,there were the fine grains of dynamic recrystallization and a large amount of unrecrystallized regions,the 18R LPSO phase played a role of dispersion strengthening in form of short rod or block.The corrosion rate was only 0.323mm/y,the tensile strength was 386MPa,and the elongation was 24.8%.The combination of low corrosion rate and high strength and toughness makes it a suitable candidate for further application.