High Temperature Deformation Behaviour of a New Magnesium Alloy

摘要

The properties and applications of magnesium alloys have been increasingly investigated due to their light weight and high specific strength. Recent studies indicate that an addition of tin (Sn) to magnesium (Mg) significantly increases the corrosion resistance of the latter. Also, the addition of calcium (Ca) increases the creep resistance of ternary Mg-Sn-Ca alloys. Therefore, such alloys have been developed to address the dual demands of high corrosion and creep resistance at service temperatures, and would be widely acceptable if they could be converted into wrought alloys. The specific alloy selected for this study is Mg3SnlCa. Though this composition is synonymous with the popular AZ31 type alloys, the microstructures of these two types are quite different. While AZ31 alloys basically involve single phase with aluminium (Al) and Zinc (Zn) present in the form of solid solution in Mg, the selected Mg-Sn-Ca alloy has two phase microstructure in the form of particles distributed in a matrix. However, such a microsturcture requires careful consideration in terms of forming operations to convert the material into wrought status. The experiments involved hot compression testing conducted over a temperature range 300 to 550 ℃ and a strain rate range 0.0003 to 10 s~(-1) using a computer-controlled servo-hydraulic testing machine. The recorded force and compression measurements are converted into corresponding stress - strain curves. Through the analysis of such results, conditions for good formability are identified along with characterization of the deformed material. It is found that this alloy is suitable for hot deformation and could be established as a new standard wrought material for applications requiring improvement in corrosion and creep resistance.