Study On Strengthening And To Ughening As-Cast AM60 Magnesium Alloy

Magnesium alloy has the advantages of light-weight, high strength/weight ratio, high stinffess/weigh ratio, high damping property and electromagnetism shielding property and so on. It has bright promise to be widely used in aviation and spaceflight, vehiele, eleetrommunieation, and is regarded as the most promising green material of the 21st century. Following with the light-weight of automobiles, more and more automobiles" components are made from magnesium alloys, where the wheels have a special magnificence and effect on the weight-save of automobiles. But Wheels should have both high strength and high toughness depending on their working environment, the magnesium alloys at present has not satisfied the requirement yet. AM60 and AZ91 are the most broadly used magnesium alloys in industry. AM60 alloy has a high ductility but its strength need to be improved.In this paper, a vacuum resistant melting furnace was used to refine AM60 magnesium alloy. By addition of different amount of alloy additive, specimens for testing were cast out of the melted metals. By using atomic Emission Spectrometry, ICP Spectrometry, XRD, metallographic microscopy, SEM and so on, the microstructure and propertities of AM60 were analyzed, and the mechanism is discussed. The main conclusions are as follows:1) Nd is important alloying element to magnesium alloys. With additions of Nd, the microstructure of as-cast magnesium alloys AM60 alloy were refined obviously.A rod-like inter metallic phase Al₁₁Nd₃ phase was observed and the volume of theβ-phase(Mg₁₇Al₁₂) somewhat decreased.More Nd addition caused further decreasing of theβ-phase and coarsening of Al₁₁RE₃. RE improved hardness and tensile properties of AM60 alloys. The ultimate tensile strength,yield strength and elongation of alloys with 0.9wt% addition of RE reached a high value, maximum tensile strength, maximum yield strength, maximum elongation are 230MPa, 127MPa and 14% respectly, and then decreased with more Nd additions.That's all caused by the wafer skilled,the second phase reference and the increase on volume and quantity of the new phase Al₁₁Nd₃.2) With additions of C into AM60 alloy, the C element was discovered mostly in the AlMn phase andβ-phase and hardly in theα-Mg phase.The C element can increase the undercooling of AM60 alloy during the solidification, so the microstructure of AM60 alloys were refined and the properties were improved. Because of different forms of C, the effects on the AM60 alloy were increased the order by graphite, coal, C fibre. The mechinacal tests incate that AM60 has the best microstructure and properties when the form of the C is C fibre.Maximum tensile and maximum elongation are 242.4Mpa and 13.2% respectively,increased by 23% and 2.5 times respectly.3) Form of failure of magnesium alloy is usually brittle through cleavage or quasi-cleavage fracture. Fracture of alloys have more characteristics of microcosmic ductility with C or Nd addition, which indicates that the addition of C or Nd can improve the ductility of AM60 alloy.