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TZM Alloy and Lanthanum Molybdenum Alloy

Molybdenum (Mo) has excellent high temperature strength, creep resistance, low thermal expansion coefficient, good thermal conductivity and corrosion resistance property, so it is widely used in the electronics industry, aerospace and military fields. However, Mo has a low recrystallization temperature, and therefore the application of pure molybdenum is often limited. Molybdenum recrystallization temperature is about 1000 ℃. Once molybdenum recrystallization, harmful impurity element is easy enrichment at the grain boundaries, thereby reducing the room temperature and high temperature performance of molybdenum. Alloying can help to improve the molybdenum’s high temperature properties. After alloying molybdenum alloy will produce solid solution strengthening and second phase strengthening, making the properties of the alloys has been improved. Analyzing lanthanum molybdenum alloy and TZM alloy’s high temperature performance plays an important role on molybdenum alloy further development.

Lanthanum molybdenum alloy and TZM alloy annealing at 1100 ℃, there are a small number of grains recrystallization, and with increasing annealing temperature, the recrystallized grains gradually increased. Recrystallized structure of molybdenum alloy exhibits elongated tissue which is different with pure molybdenum. Pure molybdenum is an isometric grain.

When the annealing temperature is less than 1400 ℃, lanthanum molybdenum alloy has a strong overall performance of strength and plasticity. When the temperature is higher than 1400 ℃, the tensile strength and ductility is decrease. TZM alloy’s tensile strength decreases with increasing temperature, but the plasticity increase, which is different with lanthanum molybdenum alloy. In addition, after comprehensive comparison, at the same temperature TZM alloy high temperature performance is better than lanthanum molybdenum alloy.

When the annealing temperature is higher than 1400 ℃, lanthanum molybdenum alloy exhibits hot brittleness which is different from the TZM alloy. This is mainly because, as the annealing temperature increase, the flow-line organization of lanthanum molybdenum alloys has a tendency to fracture. However, TZM alloy, whether in process state or recrystallization state, the size, shape and distribution of second phase are not significant changes.

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