| As a commonly used aluminum-silicon alloy,ADC12 alloy is favored by people,but ADC12 alloy also has its own limitations.For example,ADC12 alloy has insufficient wear resistance,and the texture is very soft,and it is easy to stick when used.This makes our use of ADC12 alloy somewhat restrictive.The as-cast structure has long needle-like iron phases and dendritic α-Al particles,which seriously hinder the performance of aluminum alloys.Therefore,by studying the addition of mixed rare earth Pr/Ce to modify the structure to change the mechanical properties of aluminum alloy.The modification ability of rare earth modifier is related to its atomic radius,and the modification of mixed rare earth is superimposable,and theoretically,it can carry out good modification effect on alloy.In the preparation of rare earth semi-solid slurry by high-energy ultrasonic method,the relationship between the change of the semisolid structure of the slurry and the parameters of ultrasound is studied.The apparent viscosity is measured with a rotational viscometer.Changes in microstructure,hardness and wear resistance of ADC12 alloy after adding rare earth.Studies have shown that under dry sliding friction with a slip velocity of 0.21m/s,pin-disc friction pairs are used to study the effects of different loads(20N,40 N,60N,80N)on the friction and wear behavior,and their Wear morphology analysis of wear mechanism.The results show that when the rare earth addition is 0.6%,the alloy has the best wear resistance.The wear rate and friction coefficient increase with the increase of load,and the wear mechanism of the alloy is different under different conditions.The wear mechanism of the matrix is adhesive wear and surface fatigue wear;0.3% rare earth alloy is mainly adhesive wear;0.6% alloy is mainly abrasive wear,and 0.9% is mainly adhesive wear and abrasive wear.Ultrasonic vibration method was used to prepare semi-solid alloy slurry with different rare earth(Pr+Ce)content to obtain semi-solid structure.The optimal rare earth content required for rare earth semi-solid slurry is studied,which is 0.6%.The effects of ultrasonic temperature,time and power on the microstructure of rare earth semi-solid are studied.When applying a power of 2.1kw and ultrasonic for 90 s at 600℃,a semi-solid slurry with an average grain size of 26.4μm and a shape factor of 0.83 can be obtained,which is lower than the semi-solid structure with rare earth added without ultrasound.1.7 times,the shape factor is increased by 0.63 times;compared with the semi-solid structure without rare earth ultrasound,it is reduced by 1.9 times,and the shape factor is increased by 0.8 times.The change of the microstructure is mainly due to the refinement of rare earths and the impact of cavitation and acoustic current effects caused by ultrasound,which activates particles that are not wetted or dendrites are broken or remelted,which accelerates nucleation and promotes fineness Growth of spherical particles.Study the effect of ultrasonic vibration on the rheological properties of ADC12 alloy semi-solid slurry.According to the experimental data,it can be known that the greater the solid fraction,the greater the apparent viscosity of the melt.When the ultrasonic power is low,the melt.The apparent viscosity increased significantly.When the solid phase is constant,the greater the ultrasonic power,the lower the apparent viscosity of the melt.At high power and low solid fraction,high solid fraction and low power,the apparent viscosity of the melt does not change significantly,and when the rare earth is added to 0.9wt%,the apparent viscosity at low power The change is more pronounced than under high power.The acoustic flow and cavitation effect caused by ultrasonic vibration will affect the formation of melt particles and the apparent viscosity. |
