Study On The Plastic Deformation Behaviors Of 7075z Aluminum Alloy At High Temperatures

The deformation behaviors of 7075z aluminum alloy at high temperatures have been studied by isothermal compression and extrusions tests. The interrelations of flow stress a , strain rate e, strain e and deformation temperature T for the alloy during high temperature deformation have been studied with the aid of regression analysis. Dynamic recovery and dynamic recrystallization behaviors of the alloy have also been investigated with the aids of optical microscope(OM), scan electron microscope(SEM), energy dispersion analysis of x-ray(EDAX). The flow stress equations and material constants of the alloy were derived from experimental data, and were utilized to the study of the interrelations of deformation conditions and microstructure. The effect of extrusion temperatures and speeds on the formability, microstructure and hardness of 7075z aluminum alloy have been studied primarily. The results show as follows.1. A near steady state of plastic flow of the 7075z aluminum alloy was confirmed during isothermal compression deformation at high temperature. The stress at near steady state of plastic flow decreased with the decrease of strain rate and the increase of deformation temperature. The strain-hardening index of 7075z aluminum alloy is minus value in the near steady state of plastic flow.2. The deformation of 7075z aluminum alloy at high temperature is a thermally activated process. The interrelations of flow stress and strain rate can be described by a hyperbolic sine function for 7075z aluminum alloy during the process of high temperature deformation. The flow stress at high temperature can be described by Zener-Hollomon parameter Z value.3. The predominated intenerate mechanisms of 7075z aluminum alloy during hot deformation are dynamic recovery and dynamic recrystallition. Dynamic recrystallization could only be emerged when the temperature is above or equal to 400C and InZ is less than 20.7.4. The extrudability of 7075z aluminum alloy are strongly affected by extrusion temperature and speed. The extrudability decreased with the increase of extrusionABSTRACTtemperature and speed. Extaision process of 7075z aluminum alloy ingots can be realized when the ingot was heated to 340-420℃ and the strain rate was controlled within 0 -0.101 s-1.5. The deformed microstructure and capabilities of 7075z aluminum alloy ingotsvaried a little when the heated temperature was controlled within 340~420℃ and thestrain rate was controlled within 0-0.101 s-1 . The maximum extrusion force and therising value of temperature during extrusion deformation increased with the decrease of extrusion temperature.