Study On The Mechanism Of The Effect Of Vanadium Nitride On The Corrosion And Mechanical Properties Of AZ91 Magnesium Alloy For Vehicles

Magnesium alloys are widely used in automobile manufacturing,rail transit and aerospace.Since magnesium alloys are environmentally friendly and light-weight materials,their extensive use is of great significance to energy conservation and emission reduction.However,disadvantages such as poor corrosion resistance,poor room temperature deformation performance,and poor high temperature creep resistance hinder the engineering application of magnesium alloys.Therefore,improving the performance of magnesium alloys through organization control is one of the focuses of researchers.This subject takes the automotive AZ91 magnesium alloy as the research object,adds VN particles to the alloy,and prepares VN-containing as-cast magnesium alloys by casting molding.The VN mass fractions are 0%,0.25%,0.5%,and 1%,respectively.,The cast alloy is subjected to solution treatment(400℃,20 h).Select some cast alloys,compress and deform at room temperature and high temperature 300℃,400℃,strain rate is 0.01S-1,high temperature strain is 0.7.Observe the microstructure of as-cast and thermally deformed samples by optical microscope and scanning electron microscope(SEM),use XRD and EDS to analyze the structure and second phase composition of the alloy,and use the microcomputer to control the high and low temperature electronic universal tensile testing machine for normal temperature Compression and high-temperature compression experiments,the corrosion behavior of magnesium alloys is studied through electrochemical workstation and self-installed immersion experiment device,The main experimental conclusions are as follows:1)AZ91-x.wt%VN(x=0,0.25,0.5,1)as-cast magnesium alloy is mainly composed ofα-Mg phase and β-Mg17Al12 phase.The addition of VN can make in-situ formation AlN phase,AlN phase as a heterogeneous nucleation core can effectively refine the AZ91 alloy,the alloy grain size is reduced from 139.7μm to 84.7μm.When the amount of VN added exceeds 0.25wt%,the grain size of AZ91 magnesium alloy does not decrease further.The alloy undergoes dynamic recrystallization at 300℃ and 400 thermal compression.2)The hydrogen evolution experiment results of the as-cast alloy show that the hydrogen evolution amount of the AZ91-0.25wt%VN alloy is the smallest,which is 1.75ml.The polarization curve and electrochemical impedance spectroscopy experiment results show that the AZ91-0.25wt%VN alloy has the best corrosion resistance;After thermal deformation at 300℃,the hydrogen evolution of AZ91-0.5wt%VN alloy is the smallest,2.1ml.After thermal deformation at 400℃,the hydrogen evolution of AZ91-0.25wt%VN alloy is the smallest,3ml.The polarization curve and electric The results of the chemical impedance spectroscopy experiment are consistent with the conclusions of the hydrogen evolution experiment.Under the two thermal deformation conditions,the AZ91-0.5wt%VN and AZ91-0.25wt%VN alloys respectively exhibit the best corrosion resistance.3)Compression experiment results of AZ91-x.wt%VN as-cast magnesium alloy at room temperature show that the tensile strength of magnesium alloy with 0.25%VN is increased by 51.4MPa,and the yield strength is increased by 35.7MPa;During compression at ℃,AZ91-0.25wt%VN alloy exhibits the largest peak stress of 264.96MPa.When the temperature is increased to 400℃,the peak stress of all alloys is significantly reduced,and AZ91 alloy exhibits the largest peak stress.The stress is 65.35MPa.4)The constant current discharge experiment results of AZ91-x.wt%VN as-cast magnesium alloy in 3.5%sodium chloride solution at a current density of 50mA/cm2 show that the discharge activity of AZ91-0.25%VN in constant current is the best and the potential is the most negative It is-1.36V.The constant current discharge experiment of magnesium alloy after thermal deformation at 300℃ measured:AZ91-0.25wt%VN has the best discharge performance,and its discharge potential is the most negative of-1.16V.The constant current discharge experiment of magnesium alloy after thermal deformation at 400℃ measured:AZ91-1wt%VN surface has the strongest discharge activity,and the discharge potential is-1.38V.