Study On Microstructures And Mechanical Properties Of Squeeze Cast Al-5.0 Cu-0.6Mn Alloy By Ultrosonic Treatment

With the rapid development of the aerospace and transportation,the demand for high-performance casting aluminum alloy products is increasing.The Al-Cu alloy is widely concerned because of its excellent comprehensive mechanical properties.However,the traditional casting technology has been unable to meet the requirements of high performance aluminum alloy.At present,in the process of aluminum alloy casting,the application of outfield to improve the solidification organization has been widely used.For example,squeeze casting technology is to apply pressure field.However,the single field has many limitations in the process of alloy solidification.In this paper,the influence of different parameters on microstructure and mechanical properties of the alloy was studied by using Al-5.0 Cu-0.6Mn alloys under ultrasonic-pressure compound field.the effects of pressure and ultrasonic power were studied.In addition,the second phase and the pore of the casting alloy were reconstructed by synchronous radiation X-ray tomography.The main work and conclusions are as follows:The effects of pressure,ultrasonic power,ultrasonic time and pouring temperature on microstructure and mechanical properties of Al-5.0C u-0.6Mn alloy under ultrasonic-extrusion compound field were studied by means of orthogonal test.The applied pressure and ultrasonic power are the main factors that affect the microstructure and mechanical properties of the alloy.The contribution rate is 65.4%and 29.3%respectively.The influence of microstructure on microstructure is mainly to reduce the shrinkage cavity and porosity of alloy,reduce the spacing of the secondary dendrite and refine the grain.The volume fraction of the second phase in the alloy was reduced,and more copper elements were dissolved into the matrix.The best Rockwell hardness and microstructures of the alloy could be obtained in the condition of pouring temperature 710?,applied pressure 100MPa,ultrasonic vibration power of 600w and time of 30s.The effects of ultrasonic power on microstructure and mechanical properties of Al-C u alloy under gravity casting and squeeze cast were studied.Both gravity casting and squeeze casting,the increase of ultrasonic power makes alloy rockwell hardness increased,but the effect is not linear,when ultrasonic power is greater than 600 w the effect is not obvious.The increase of ultrasonic power increases the so lidification speed of the alloy,and decreases the spacing of the secondary dendrites,and the distribution of the second phase in the matrix is even,which is more obvious in the alloy of extrusion casting.In addition,the increase of ultrasonic power also reduces the shrinkage cavity and porosity in gravity casting al oy.The second phase and the 3d morphology of the hole were reconstructed by the synchronous radiation X-ray imaging technology.Under the power of 300w,the volume fraction of Al₂Cu phase in alloy is 5.04%.Under the power of 900w,the volume fraction of Al₂Cu phase in alloy is 2.34%.The increase of ultrasonic power makes the Al₂Cu phase in the alloy become the ellipsoid and rod shape of the scattered distribution.Moreover,the distribution peak of mean curvature of Al₂C u was increased.The results of skeletal analysis show that the number of Shared nodes decreases,but the average length distribution of Al₂C u phase increases.The pore in the alloy is mainly the shrinkage holes of the dendrite,which is flat irregular shape.With the increase of ultrasonic power,the volume of the maximum pore in the al oy decreased significantly.