Effect Of Ti And Sm Composite Addition On The Organization And Properties Of AZ91D Magnesium Alloy

AZ91D magnesium alloy is widely used in aviation,automotive,medical and other fields due to its excellent performance.However,poor corrosion resistance has hindered further development.Microalloying is one of the research and development pathways for high-performance magnesium alloys,which studies the microstructure and properties of microalloyed magnesium alloys.This article mainly uses AZ91D magnesium alloy as the basic material and uses a high vacuum melting furnace to prepare intermediate alloys.Ti and Sm are added to AZ91D magnesium alloy through intermediate alloying for alloying.And analysis methods such as optical microscopy,X-ray diffractometer,scanning electron microscopy,and electrochemical workstation are used.Study and analyze the effect of Ti and Ti,Sm composite addition on the microstructure and properties of AZ91D magnesium alloy,and obtain the optimal alloy ratio to achieve the best alloy performance.At the same time,use cryogenic treatment methods to study the effect of cryogenic treatment on the microstructure and properties of AZ91D-0.1Ti-1.5Sm magnesium alloy.The experimental results show that the microstructure of AZ91D magnesium alloy is significantly improved by adding trace Ti into AZ91D magnesium alloy.Where,The phaseβ-Mg₁₇Al₁₂changes from net structure to granular and short rod structure,resulting in more uniform structure.With the addition of Ti,the tensile strength and hardness of AZ91D magnesium alloy are improved.All increase first and then decrease,the optimum addition of Ti is 173 Mpa and 67.54 HV respectively when the content is 0.1%.32%and 18.2%higher than the matrix respectively.The addition of Ti also improves the corrosion resistance of AZ91D magnesium alloy.The main factor is the reduction of micro-galvanic corrosion and the purification of the melt.The effect of Ti and Sm on AZ91D magnesium alloy is better than that of Ti alone.Ti and Sm can form Al₂Sm phase,which can be heterogeneous nucleation point.When the content of Ti is 0.1%and Sm is 1.5%,the performance of AZ91D magnesium alloy is the best and its structure is obviously refined.β-Mg₁₇Al₁₂phase is evenly dispersed in the matrix.The addition of Ti and Sm can improve the microstructure and properties of AZ91D magnesium alloy.When 0.1%Ti and 1.5%Sm are added,the tensile strength,elongation and hardness of AZ91D magnesium alloy are 189 MPa,4.9%and 69.5 HV,respectively.The optimum addition of Ti was increased by 9.2%,26.2%and 2.9%compared with that of Ti.Corrosion weight loss rate of alloy is 0.1825×10^-4g/（cm²*h）.It is also better than adding Ti separately.The AZ91D magnesium alloy with compound addition of 0.1%Ti and 1.5%Sm was treated by cryogenic treatment.The results show that the performance of AZ91D-0.1Ti-1.5Sm magnesium alloy can be improved by cryogenic treatment within a certain range.After cryogenic treatment for 12 h,the tensile strength and elongation of AZ91D-0.1Ti-1.5Sm magnesium alloy were improved.196 MPa and5.13%respectively.The corrosion resistance of the alloy has also been improved with the corrosion weight loss rate of 0.1468.×10^-4g/（cm²*h）.19%less than the sample that is not very cold.The corrosion potential increases and the corrosion current density decreases.The performance of AZ91D-0.1Ti-1.5Sm magnesium alloy decreases with the prolongation of cryogenic treatment.