Deformation behavior of 7475 aluminum alloy at high temperatures

Deformation behavior of the 7475 aluminum alloy was studied in temperature range T=623-793K by compression test. It has been shown that the 7475 alloy exhibits a threshold behavior. Analysis in terms of threshold stress has shown that there are two characteristic modes of deformation behavior in the power-law regime in the examined temperature range. At normalized strain rate (epsilon)over dotRT/D(1)Gb less than or equal to 1.6.10(13) mol(-1) the value of the stress exponent, n, is equal 4, and at normalized strain rate (epsilon)over dotRT/D(1)Gb greater than or equal to 1.6.10(13) mol(-1) the value of the stress exponent, n, is equal 6. Value of activation energy is close to that for lattice self-diffusion in pure aluminum at temperatures above 763K and close to the value of pipe diffusion at T less than or equal to 723K. Deformation behavior of the 7475 alloy was interpreted in terms of transition from low temperature climb to high temperature one. Two types of temperature dependence of threshold stress was observed in the examined temperature region. Strong temperature dependence with the energy term, Q(o)=130 kJ/mol was revealed at T=743-793K. At T=673-743K the dependence with Q(o)=42 kJ/mol was found. The role of second phase dissolution in threshold behavior of the alloy is considered.