An investigation on the microstructure of an AM50 magnesium alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 355; no. 1; pp. 201 - 207
• Main Authors: Wang, R.M., Eliezer, A., Gutman, E.M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.08.2003; Elsevier
• Subjects: AM50 magnesium alloy; Applied sciences; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Dislocation; Elasticity. Plasticity; Exact sciences and technology; Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, epr, nmr, etc.); Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Physics; Structure of solids and liquids; crystallography; Mechanical properties; AM50 magnesium alloy; Microstructure; Dislocation; Particle size; Stress strain relation; Slip plane; Dislocation structure; Precipitate; Experimental study; Tension test; Cast alloy; Grain boundary; Magnesium base alloys; Transmission electron microscopy; Yield strength; Dislocation pile up
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(03)00065-0

The microstructure and the dislocation arrangement in the die cast AM50 magnesium alloy as well as in the stressed states have been investigated using conventional transmission electron microscopy (TEM), high-resolution TEM and energy dispersive X-ray analysis. The microstructure of the die cast AM50 alloy is found to mainly consist of α-Mg, β-Mg 17Al 12 and Al 8Mn 5 phases. Two kinds of β-Mg 17Al 12 particles with different sizes have been found in the stressed AM50 magnesium alloy. Besides the normal β-Mg 17Al 12 particles with size around several micrometers as in the die-cast AM50 magnesium alloy, some finer β-Mg 17Al 12 particles in the stressed states of the AM50 alloy have also been found. The finer β-Mg 17Al 12 particles are found to be only about tens of nanometers with oval or rod-like morphology, which may be formed during deformation. Dislocation pile-ups have been found in the stressed AM50 alloy for the first time. The spacing between each parallel dislocation in the pile-ups is only several nanometers. The dislocations are confined in the slip planes and piled up against grain boundaries. Dislocations in the networks are found to increase with deformation of the alloy. Also, dislocation networks have been found in the β-Mg 17Al 12 and Al 8Mn 5 phases as well as in the matrix in the deformed AM50 magnesium alloy. However, the dislocation pile-ups are found to be almost identical from 1.3% deformation to rupture, which explains the stable tensile yield strength of the AM50 magnesium alloy during the deformation.