Microstructure and superplasticity of Mg–Al–Ca electromagnetic casting alloys after hot extrusion

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 494; no. 1-2; pp. 391 - 396
• Main Authors: Kim, W.J., Lee, K.E., Park, J.P., Kim, M.G., Wang, J.Y., Yoon, U.S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25-10-2008; Elsevier
• Subjects: Applied sciences; Calcium; Elasticity. Plasticity; Exact sciences and technology; Extrusion; Grain refinement; Magnesium alloys; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Superplasticity; Superplasticity; Extrusion; Calcium; Magnesium alloys; Grain refinement; Constitutive equation; Grain size; Tensile property; Thermal stability; Cast alloy; Casting; Magnesium base alloys; Elongation at fracture; Electromagnetic stirring; Fine grain structure; Microstructure; Strain rate
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2008.04.041

Microstructure and superplastic properties of the plates extruded from the Ca containing Mg alloy (1wt.% Ca–AZ31) billets fabricated by electromagnetic casting (EMC) without and with electromagnetic stirring (EMS) were examined. The linear intercept grain sizes of the extruded materials were 3.7μm and 2.1μm, respectively. The material extruded from the EMC+EMS billet exhibited good superplasticity at low temperatures as well as at high strain rates, including the tensile elongations of 370% at 1×10−3s−1, −523K and 550% at 1×10−2s−1, −673K. These values largely exceeded those of the AZ31 alloys with the similar grain sizes. The superior superplasticity of the extruded EMC+EMS billet could be attributed to fine grains and high grain stability at elevated temperatures by the presence of finely dispersed particles of thermally stable (Al,Mg)2Ca phase. The constitutive equations were developed for describing the high-temperature deformation behavior of the fine-grained 1wt.% Ca–AZ31 alloys with different grain sizes in wide range of temperature and strain rate.