Researches On The Microstructure Evolution And The Corresponding Damping Capacities And Mechanical Properties Of Mg-Ce Alloys

With the rapid development of modern society, the equipments increasingly motors and complication, structure function integration and lightweight magnesium materials will be the focus of future development to reduce energy consumption and anti-vibration noise reduction. However, most studies are focused on mechanical or single function characteristics of Mg alloy, research and development at the same time with good mechanical and damping properties of structure function integration of Mg alloy is serious shortage. Moreover, the existing high strength and high damping Mg alloys containing a large amount of rare earth elements, high production costs and processing difficulties, which greatly limits its large-scale and high-value application.In this study, based on the Mg-Ce alloy series, high damping and high strength of Mg-X-Ce alloys were designed and prepared by adding different solubility of Mn, Zn and Sn non-rare-earth elements. Alloying design, extrusion deformation and heat treatment were jointly used to control the second phase content, distribution, grain size and texture intensity, which achieve the optimal balance of damping and mechanical properties of Mg-X-Ce alloys. The design criterion of high damping and high strength Mg alloys was obtained for low-cost structure function integration of the new magnesium materials with different actual requirement.Firstly, mechanical and damping capacities of Mg-Ce binary alloys with different Ce content were investigated. Many long straight and parallel second phases appeared in as-cast Mg-2Ce alloy, while this special microstructure won't found in the other three alloys. The emergence of parallel second phase was conducive to the damping performance, the damping value with strain at 10-3 was 0.084, which may related to dislocation density and stress concentration. After extrusion, mechanical properties greatly improved but damping capacity declined. In addition, as-extruded Mg-0.5Ce alloy showed good comprehensive properties, its yield strength is 356.7 MPa, tensile strength is 357.6 MPa, elongation is 5.8%, and damping value Q-1(?=10-3) is 0.015.Secondly, the effect of Mn content on microstructure, damping and mechanical properties of Mg-Ce alloys were studied on the basis of Mg-0.5 Ce. It was found that the damping performance of as-cast Mg-Mn-Ce alloy is hardly influenced by the change of Mn content. The strength and elongation of as-extruded Mg-Mn-Ce alloys increase first and then decrease with the increase of Mn content. The J-MC3 alloy exhibited good comprehensive mechanical properties, its tensile strength is 339 MPa, yield strength is 330 MPa, and elongation is 11.2%. Furthermore, the addition of Mn element in improving mechanical properties of the alloy while maintaining its internal friction.Then, microstructure, damping and mechanical properties of Mg-Ce alloys with the higher solubility of Zn, Sn elements were investigated. The second phase of as-cast Mg-Zn-Ce alloys gradually from the parallel distribution into dispersion with the increase of Zn content and its damping performance is low. However, the alloy phase of as-cast Mg-Sn-Ce alloys are parallel distributed with the high solubility of Sn content increases, SC3 alloy showed good damping capacity and its specific damping capacity(SDC) is up to 54%. After extrusion, the damping capacities of Mg-Zn/Sn-Ce alloys presented first increase and then decrease. Among them, the J-ZC2 alloy exhibited good comprehensive mechanical and damping properties, the yield strength of 293 MPa, the tensile strength of 314 MPa, the elongation is 6.1%, and the damping value Q-1 is 0.034. J-SC3 alloy also showed excellent comprehensive performances, YTS = 135 MPa, UTS = 227 MPa, EL = 8.9% and Q-1 = 0.055.Finally, the damping and mechanical properties of as-extruded Mg-X-Ce alloys were optimal balanced by the appropriate heat treatment.The experimental results showed that the second phase content, morphology and quantity of grain boundary as a strong pinning point is the important factors that affect damping and mechanical properties of Mg alloys. Heat treatment can effectively change the microstructure of Mg-Zn/Mn-Ce alloys, which resulted in the reduction of mechanical properties and damping capacity is greatly improved by more than 40%. TJ-ZC1 alloy exhibited excellent comprehensive properties after heat treatment at 350?x4h, namely YTS = 201 MPa, UTS = 266 MPa, EL = 18%, and SDC = 69%.