Influence Of Zn Contents On Hot Deformation Behavior Of Al-Zn-Mg-Cu Alloys

Al-Zn-Mg-Cu alloy is widely used in transportation,aerospace and aviation industry due to its characteristics of stress corrosion resistance,high room temperature strength and good comprehensive properties.At present,the research on the rheological stress behavior of the thermal deformation of Al-Zn-Mg-Cu alloy at home and abroad is aimed at a single alloy.In this paper,three kinds of Al-Zn-Mg-Cu alloys with different Zn content were subjected to isothermal single pass heat compression test by Gleeble-3500 thermal simulation test machine.The deformation temperature is 300?450?,and the strain rate is 0.01?10s-1,The true stress-strain curves of three different Zn contents are obtained?The true stress true strain curves of three different Zn contents were obtained,and their constitutive equations and material constants were established.At the same time,by establishing the thermal processing map of Al-Zn-Mg-Cu alloy with different Zn content and analyzing the microstructure of the specific area,the best range of hot working process is obtained?The main results are as follows:(1)The Al-Zn-Mg-Cu alloy with different Zn content showed the same change rule,and the flow stress increased rapidly with the increase of strain,reached the peak and then decreased gradually,and entered the steady deformation stage.(2)The peak stress of Al-Zn-Mg-Cu alloy with Zn content of 7.93wt.%is slightly higher than the peak stress of Al-Zn-Mg-Cu alloy with Zn content of 6.25wt.%and 10.1wt.%.(3)Flow stress behavior of Al-Zn-Mg-Cu alloys can be described by a Zener-Hollomon parameter in the hyperbolic sine equation.When the Zn/Mg ratio is greater than 3,the thermal deformation activation energy increases first and then remains the same with the increase of Zn.(4)According to the thermal processing map and the microstructure of the specific area,the power dissipation coefficient of three Al-Zn-Mg-Cu alloys with different Zn content increases with the increase of deformation temperature and strain rate.When the deformation temperature is high and the strain rate is low,the structure is well.The machining defects of holes and cracks appear in the unstable region.(5)The best heat processing process parameters of three kinds of Al-Zn-Mg-Cu alloys with different Zn contents were:The deformation temperature of the alloy with Zn content of 6.25wt.%is 380?450?,and the strain rate 0.01?0.2s-1;The deformation temperature of 10.1wt.%alloy with Zn content of 7.93wt.%is 400?450?.the strain rate 0.01?0.2s-1.