Deformation Behavior and Controlling Mechanisms for Plastic Flow of Magnesium and Magnesium Alloy

Abstract

Deformation behavior of pure Mg and Mg alloy were studied in the temperature range of 423 to 773 K and at strain rates of 10 À4 -10 À2 s À1 . Three temperature regions can be categorized both in Mg and Mg alloy. The deformation behavior in Mg can be described by an exponantional law at temperatures below 523 K. At the higher temperatures a power law of deformation is valid with the stress exponent close to n ¼ 7 in the intermediate (523-623 K) and 2.2 in the high (673-773 K) temperature ranges. The alloying of Mg with elements such as Zn changes the phenomenology of plastic deformation. An exponantional law is operative at temperatures below 473 K. At above 473 K deformation obeys a power law. The stress exponent is close to n ¼ 7 at intermediate temperatures (473-523 K) and 5 in the high temperature range. An analysis of experimental results shows that alloying changes the controlling mechanisms of plastic deformation and so leads to different deformation behavior in pure Mg and Mg alloy that can be associated with decreasing stacking fault energy (SFE) in Mg alloy. The effect of SFE on the mechanisms of plastic deformation when alloying Mg is discussed.

Solid Solution Softening Mechanisms in Mg-Ca Alloy

“…The rate-controlling process for plastic deformation is the movement of screw dislocations for both BCC and HCP metals. [30][31][32][33][34][35] For example, the rate-controlling process of Mg is the cross slip of screw dislocations from the basal plane to nonbasal planes. In BCC and HCP metals, because the Peierls stress for screw dislocations is large, the solid solution softening effect is large.…”

Hardness Variation and Strain Distribution in Magnesium Alloy AZ31 Processed by Multi‐pass Caliber Rolling

“…In order to obtain the true stress, s, -true strain, e, relationships depending on strain rates as materials data in the FEA, the compression tests of a cylindrical specimen with lubricant were conducted for strain rates from 0.0033 to 0.7 s À1 at 473 K. Experimental data up to a true strain of 0.7 were used to avoid excessive inhomogeneous deformation due to barreling. The data represented a typical s-e relationship of the dynamic recrystallization (DRX) type [27][28][29] in small strain range of 0 < e <0.7, as shown in Figure 2.…”

Continuum modeling of the response of a Mg alloy AZ31 rolled sheet during uniaxial deformation

“…In particular, at this point it is key to develop simulation models that, supported by the experimental data available, can predict of the response of Mg alloys under different service conditions. The deformation mechanisms of Mg and Mg alloys that are operative at low strain rates have been extensively investigated over the past years (Couling et al, 1959;Kocks and Westlake, 1967;Kelley and Hosford, 1968a;Couret and Caillard, 1985;Chin and Mammel, 1970;Yoo, 1981;Vagaralia and Langdon, 1981;Zelin et al, 1992;Munroe and Tan, 1997;Agnew et al, 2001;Watanabe et al, 2001;Barnett, 2001;Agnew et al, 2003;Galiyev et al, 2003;Koike et al, 2003;Barnett, 2003;Gehrmann et al, 2005;Barnett et al, 2004a;Agnew and Duygulu, 2005;del Valle et al, 2005;Keshavarz and Barnett, 2006;Meza-García et al, 2007;Barnett, 2007;del Valle and Ruano, 2007;Al-Samman and Gottstein, 2008;Chino et al, 2008;Jain et al, 2008;Hutchinson et al, 2009;Ball and Prangnell, 1994;Lou et al, 2007). Slip in hexagonal close packed (HCP) metals may take place along the h11 20i (hai) direction on basal and non-basal (f10 10g-prismatic, f10 11g-pyramidal) planes.…”