| Magnesium is the lightest and the most widely used engineering structural materials at the present time, which has less density, highly specific strength and stiffness, good damping capacity, superior electromagnetic shielding, good machining performance, excellent processing performance and good casting performance advantages, in recent years, it becomes the important lightweight materials in automotive, electronics, aerospace industry. AZ31 wrought magnesium alloy is one of the most widely used in industry of wrought magnesium alloy, which has good mechanical properties at room temperature, good ductility, good tensile strength and excellent resistance to atmospheric corrosion. At present, the mainly production methods for all kinds of industrial use magnesium alloy's is casting. But to integrate, the mechanical properties of magnesium alloys, especiallly the strength, toughness and ductility to be further enhanced, AZ31 wrought magnesium alloy strength and deformation ability always needs to be further improved, so we study the alloying elements on the AZ31 wrought magnesium alloy, it will have special significa- nce for the AZ31 wrought magnesium alloy's structure and the properties. Adding rare earth elements in magnesium alloys can effectively improve the overall performance of magnesium alloy, and in the heat-resistant magnesium alloy, the rare earth magnesium alloy occupies a special position, in the most countries the rare earth magnesium alloy account for more than 50% in the totally magnesium alloy. In this thesis based on AZ31 wrought magnesium alloy, using optical microscopy (OM), X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), energy dispersive spectroscopy, tensile tests and hardenss tests and other analysis methods, read up the effect of Nd, Ce and La on organization and mechanical properties of AZ31 wrought magnesium alloy .The results show that by adding an appropriate amount of Nd, Ce and La can significantly refine AZ31 wrought magnesium alloys, change alloy microstructure and precipitate morphology, and increase alloy hardness, tensile strength and the elongation. When Mixed Nd, Ce and La in AZ31 magnesium alloys, along with the increaseing amount of rare earth elements , we can find that mechanical properties of the alloy was first increased and then decreased. When the rare earth elements Nd, Ce and La, the respectively addition is 0.4%, 0.8%, 0.4%. The maximum hardness as-cast alloy and solution and aging state, respectively is 78HB and 95HB, 78HB and 95HB, 77HB and 93HB. The performance of AZ31 wrought magnesium alloy is increased by 10% and 34%, 10% and 34%, 9.8% and 31% than no mi-xed rare earth elements;When the rare earth elements Nd, Ce and La, the respectively addition of 0.4%, 0.6%, 0.4%, the highest room temperature tensile strength of alloy is 168MPa, 167MPa, 166MPa. The performance of AZ31 wrought magnesium alloy is increased by 46.1%, 45.2%, 44.3% than no mixed rare earth elements;When the rare earth elements Nd, Ce and La, the respectively addition of 0.2%, 0.3%, 0.6%. the maximum room temperature elongation of alloy is 11.8%, 11.7%, 11.73%. The performance of AZ31 wrought magnesium alloy is increased by 10.3 %, 9.4%, 9.6% than no mixed rare earth elements.AZ31 wrought magnesium alloy by adding rare earth elements mixed Nd, Ce and La, alloy mesh with most of the beginning of Mg17Al12 fracture,it is bone-like or granular dispersed spread over in the alloy grain boundaries and grain interior. And it is appeared a lot of needle-like or discoid rare earth compounds Al4Ce, Al2Nd and Al4La in the organization. AZ31 wrought magnesium alloy's organization and performance have been significantly improved and enhanced.Experimental studies have shown that mixing by adding three kinds of rare earth elements Nd, Ce, La, Nd is three kinds of rare earth elements on AZ31 magnesium alloy as-cast, solution and aging state of hardness, tensile strength and elongation. |
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