Microstructural evolution of AZ61 magnesium alloy during hot deformation

Abstract

The microstructural evolution of AZ61 magnesium alloy during hot compression at various temperatures was investigated. The experimental results show that dynamic recrystallisation occurs over a wide temperature range. Grains can be greatly refined through dynamic recrystallisation. The mean size of the recrystallised grains increases with a decrease of temperature or value of Z (Zener -Hollomon parameter), while the reciprocal of the recrystallised grain size has a good linear relationship with the natural logarithm of the Z value, as well as the hyperbolic term of the flow stress. Basal and non-basal segments have been found in both recrystallised grains and primary grains, whereas dislocation pileups exist only in recrystallised grains when the temperature is lower than 673 K. The occurrence of twins is dependent on temperature and strain. When the strain increases, primary twins evolve into secondary twins. However, secondary twins grow with an increase of temperature; some secondary twins evolve into subgrains.MST/6033

Study of the plastic flow behaviors of AZ91 magnesium alloy during thermomechanical processes

“…Comparison between these˛values of magnesium alloys indicates that there is no large deviation among them, although they have been obtained from the researches with different magnesium alloys and different conditions [6,8,9]. This consistency suggests that magnesium-based alloys, or at least Mg-Al-Zn series have alike values of˛, which may not have significant dependence on other factors like grain size, precipitation condition, etc.…”

“…This consistency suggests that magnesium-based alloys, or at least Mg-Al-Zn series have alike values of˛, which may not have significant dependence on other factors like grain size, precipitation condition, etc. Since the deduced value of˛is much close to the results of the studies [6,8,9], it is used in the following constitutive studies.…”

“…In another study of high-temperature (250-400 • C) deformation of the AZ61 alloy that was heat treated (400 • C/16 h) from as-cast, Q was reported to be 160 kJ/mol [9]. It can be found that these Q values are all larger than the activation energy for diffusion or creep, indicating that these deformation behaviors are not primarily controlled by the general diffusion mechanism, which may dominate at low-temperature regimes and small strain rate.…”

“…Because the alloys were all solutionized before deformation in Refs. [8,9] and the present article, the ␤ phase can rationally be treated as completely dissolved. Thus, the effect of solute dragging effect on dislocations should be strongest in AZ91 alloy.…”

“…By studying the high-temperature (200-400 • C) deformation of AZ31 alloy of equiaxed and coarse grains, Spigarelli deduced that the value ofį s 0.02 MPa −1 [8]. Zhou studied the high-temperature (250-400 • C) compression behavior of the AZ61 alloy that is prepared by gravity cast and 400 • C/16 h solutionizing treatment, and reported that the value of˛is 0.02 MPa −1 [9].…”