It is well known that magnesium alloys have many excellent and unique properties, such as low density, high specific strength and stiffness, perfect damping capacity and shock energy absorption capacity, easy processing, as well as a good recycling capacity and compatibility with environment, and the resource of the magnesium is very abundant in the nature. Therefore, it is believed that magnesium alloy can be one of the most hopeful metallic materials adopted in the high-tech industry facing 21st century. ...