A Comprehensive Study Of Rheological Behavior Of Light Alloys Using Thermo-simulation Test And Crystal Plasticity Theory

Along with the development of the aerospace industry and the increasingly strict requirements for the lightweight, light alloy is more and more widely applied in industry area like aluminum, titanium and magnesium etc. Thermoplastic forming is an important way of promoting the light alloy products manufacturing, to fully understand the macro forming conditions and mesoscopic structure on the mechanical behavior of hot forming comprehensive effect has important theoretical and practical value.In this paper, the isothermal compressive tests that follow a typical procedure were conducted on a Gleeble-1500 thermo-simulator for Al 7050 and Ti-6Al-4V in a wide hot forming domain. Johnson-Cook(JC) model and Arrhenius hyperbolic sine(A-type) models are established based on the data obtained by compression test. Then, the two models has been coupled in the finite element software DEFORM 3D and analyze the whole package of them from the distribution of stress, strain and the outfit after compression. Finally, attempting to explore the rheological behavior of the polycrystalline material in microscopic combined with crystal plasticity theory and finite element simulation. The main conclusions are as follows:① The flow stress of two kinds of materials increases with strain rate increasing, decreases with the temperature rising during the high temperature compression deformation.② In the analytical calculation on directly, the accuracy of JC model is low. However, the A-type model with strain compensation has a higher predict capability even outside the fit domain.③ In finite element simulation, to compare the normal stress on the surface of the sample, the σz calculated through a variety of methods has a huge different, even though the results of analytical calculation and simulation has good consistency. The constitutive model has a relative small impact on the flow behavior of metals. The goodness of fit between the result of direct calculation and simulation based on A-type model is not as good as the JC model if A-type model don’t take the strain compensation into consider.④ Combining the theory of crystal plasticity and element simulation, the change trend of total grain interface in the process of the cylinder upsetting are first decreases and then increases with the increasing deformation. As the orientation of polycrystal body is anisotropy, the coordinate relationship of adjacent grains will be less because of the similar orientation, and the deformation will be easier, thus the grain boundary square come to the minimum value faster. The increase of the grain boundary is lager with the developing of the deformation when the grain is isometric, it leads to the dislocation’s motion is blocked at the boundary. Fewer numbers of grains possess bigger grain size; strain distribution is more uniform and concentrated around the boundaries.