Prediction of Flow Stress and Characterizing the Deformation Mechanism of As-Extruded 7005 Aluminum Alloy

This study explores isothermal hot compression of the as-extruded 7005 aluminum alloy within a temperature range of 573-823 K, with strain rates from 0.001 to 1 s(-1) and a strain of 1.2. Three constitutive equations, employing hyperbolic sine, power law, and exponential functions, were formulated and compared to predict rheological peak stress accuracy and applicability. The results indicate that the hyperbolic sine function is suitable across all stress levels, the power law function for low stress (<56 MPa), and the exponential function for high stress (>56 MPa). Introducing a strain compensation function enhances hyperbolic sine function accuracy. The stress exponent (n) and activation energy (Q) decrease with increased deformation, indicating a transition in the deformation mechanism from early-stage dislocation climb to later-stage dislocation glide. At 773 K with strain >0.6, the presence of precipitates maintains the n value at approximately 4. Solute atoms (Zn, Mg, and Zr) and precipitates (MgZn2 and Al3Zr) impede diffusion and dislocation motion, resulting in deformation activation energies surpassing pure aluminum. Additionally, kernel average misorientation maps demonstrate that higher deformation temperatures and lower strain rates reduce internal residual stresses.