Ce Content On Microstructure And Thermal Aconductivity Of Mg-Zn-Zr Alloy Sexual Influence

Magnesium alloy is known as"green material for the 21st century".Because of its high specific strength,good casting performance and high thermal conductivity,it is expected to become the third largest basic metal structural material after steel and aluminum.Studies have shown that adding rare earth elements to a magnesium alloy can not only improve the structure of the magnesium alloy,but also improve the mechanical properties and corrosion resistance of the magnesium alloy.In this paper,Mg-Zn-Zr alloy system was selected as the research object,and 0.5%Ce,1.0%Ce,1.5%Ce were added respectively to prepare magnesium alloys with different rare earth contents,and then the solution of the research sample was 430?×24h solid solution treatment,followed by aging treatment at 200?for 24h.Using optical metallurgical microscope,X-ray diffractometer,scanning electron microscope,energy spectrometer,transmission electron microscope and laser thermal conductivity instrument,etc.,the effect of different compositions and different heat treatment processes on the microstructure of the alloy was studied;HV-50A dimension was used The Vickers hardness of the alloy was measured by the Vickers hardness tester,and the influence of the microstructure and the rare earth element Ce on the mechanical properties of the Mg-Zn-Zr alloy was analyzed.Based on the influence of the thermal conductivity,the method of improving the thermal conductivity of the magnesium alloy was explored.It can provide theoretical basis and data support for the development of low-cost,structure-function integrated magnesium alloy.The research shows that the as-cast Mg-Zn-Zr alloy is mainly composed of??Mg?matrix and Mg₇Zn₃ phase.As the content of rare earth element Ce increases,the volume fraction of the second phase in the alloy increases,Mg₁₇Ce₂ phase is formed at the grain boundary,and the formation of the magnesium-zinc phase is suppressed,the shape changes to a network,and the continuity of the grain boundary is also enhanced.As the content of Ce in the rare earth element increases,Zn atoms gradually segregate toward the grain boundaries and coincide with the segregation of Ce atoms.The lattice distortion of the matrix decreases continuously with the increase of Ce content,and the thermal conductivity also shows a downward trend.The solution treatment dissolves the Zn atoms back,and the amount of Mg₁₇Ce₂increases relatively,in the form of particles,intermittently distributed in the grain boundaries.The volume fraction of undissolved second phase still increases with the increase of Ce content.Mg₇Zn₃ is almost completely dissolved,and the second phase precipitate remaining on the grain boundary is only the Mg-Ce compound.The degree of lattice distortion has increased compared with the as-cast state,and the thermal conductivity tends to decrease as the content of Ce in the rare earth increases.After aging treatment,MgZn phase and Zr₂Zn₃ phase precipitated,and the precipitates on the grain boundary were obviously more than the solid solution state.The thermal conductivity after aging treatment is better than that in the as-cast state and the solid solution state;as the temperature increases,the thermal conductivity of the alloy also increases.Under different heat treatment conditions,the existence form and position of solute atoms are different,resulting in different degrees of lattice distortion of the matrix;the solid solution elements of the alloy,the number of the second phase,and the distribution of the second phase all affect the thermal conductivity of the alloy,resulting in solid solution heat conduction The rate is the lowest,the casting state is centered,and the aging state thermal conductivity is the best.The hardness,tensile strength,and elongation of the as-cast,solid-solution,and aging alloys increase with the increase of Ce content.Under different heat treatment conditions,the solid-solution hardness is the lowest and the tensile strength is the lowest.Excellent,similar to the law of thermal conductivity;the elongation of the alloy is the lowest in the aging alloy and the highest in the solid solution alloy.