1. Magnesium alloy
To further reduce the weight of the train, magnesium alloys can be an option. The composition of the commonly used magnesium alloy extruded profiles and rolled sheets and the properties of the corresponding post-treatment methods are shown in Figure 1. Magnesium resources are particularly abundant in the world. Iron can only be mined for more than 100 years, aluminum can be mined for about 300 years, and magnesium can be mined for more than 1,000 years. China’s primary magnesium production accounts for about 40% of global production. In addition, the density of magnesium is only 1.7g/cm³, which is 2/3 of aluminum and 1/4 of steel, and its specific strength is higher. The E value is only 0.45MPa, which is 2/3 of aluminum and 1/4 of steel. The change law of the structure, composition and properties of magnesium alloy is similar to that of aluminum alloy, its strength is similar, and its welding method is the same, but its specific strength and specific stiffness are higher, and its lightweight effect is better.
2. Titanium alloy
The density of titanium is 4.5g/cm³, which is higher than that of aluminum and magnesium, but the strength is very high, the specific strength is high, and the welding method is similar to that of aluminum-magnesium alloy welding. The composition properties of different microstructure types of titanium alloys are shown in Figure 2. Taking the commonly used TC4 titanium alloy (Al5.5~6.8, V3.5~4.5, other Ti) as an example, it has been proved by tests that the strength of argon arc welding and plasma arc welding reaches 1006MPa, which is close to the strength of the base metal of 1072MPa; the elongation rate is 5.9 %~6.9%, which is 50% lower than the base metal. Titanium alloys have been widely used in aerospace vehicles, and are also the direction of the development of high-speed train body material welding structures.
