Titanium alloy elimination process and annealing process

In addition to recrystallization in a-titanium alloy and a β-titanium alloy, there are also changes in composition, quantity and morphology of a-phase and β-phase. It is also complicated to determine the annealing process. For the delivery status of the metallurgical plant, it is mainly required to have a stable and plastic structure. The annealing temperature is generally selected to be 120 to 200 ° C below the a β / β phase transition point, and the cooling method is also air cooled. However, for the final annealing of the product, the influence of the annealing process on the microstructure and mechanical properties must be determined by experiments.

The time required for stress relief annealing depends on the thickness of the workpiece, the small residual stress, the annealing temperature used, and the degree to which stress is desired to be removed. Refer to the case of stainless steel when considering the thickness of the workpiece. The temperature chosen and the degree of stress relief desired are generally determined experimentally. The effect of heating temperature and holding time on the residual stress of TC4 titanium tube and titanium alloy. Obviously the heating temperature is high and the time required is short.

The cooling method for stress relief annealing generally uses air cooling. Furnace cooling can also be used for parts of large size and shape. Titanium alloy stress relief annealing system. Within the recommended temperature and time range, it should be determined by experiment based on the above principles. It should be noted that the stress relief annealing of titanium weldments is often considered in conjunction with subsequent heat treatment. The stress relief annealing of the cold formed part is performed simultaneously with the hot orthopedic process, but the contamination of the workpiece by the jig should be avoided.

In the complete annealing process, the purpose of the complete annealing of the titanium plate and the titanium alloy is to obtain a stable, plastically good or a certain comprehensive performance of the microstructure. Recrystallization occurs mainly in this process and is therefore also referred to as recrystallization annealing. In addition, there are also changes in the composition, morphology and quantity of the a phase and the beta phase. Most of the a and a beta titanium alloys are used in a fully annealed condition. The two-phase region of the all-a-type titanium alloy is small, and recrystallization occurs mainly during the complete annealing process. The annealing temperature is generally selected to be 120 to 200 ° C below the a β / β phase transition point. Excessive temperature causes unnecessary oxidation and grain growth, and the temperature is too low and recrystallization is incomplete. The cooling rate has little effect on the microstructure and properties of such alloys, and air cooling is generally used.

As for the metastable β-type titanium alloy, complete annealing is also a solution treatment. The annealing temperature of the metallurgical plant before leaving the factory is generally selected from 80 to 100 °C above the a β/β phase transition point. Within the recommended full annealing process, the specific process shall be determined experimentally based on the material's processing history, actual chemical composition, and equipment used. In order to avoid unnecessary oxidation, the lowest temperature and the shortest time should be used when the process is selected to meet the performance requirements.

A beta annealing process has appeared in recent years. The titanium alloy and the a β titanium alloy are air-cooled after heating in the β phase region, and a needle-like (or sheet-like) a is precipitated on the coarse β crystal grains. This type of structure corresponds to higher fracture toughness, creep resistance and notch sensitivity, but decreases the plasticity index such as the area shrinkage. Where appropriate, this can be used as appropriate. In addition, for some alloys, when it is required to improve the performance stability of working for a long time at the use temperature, a second annealing higher than the use temperature, or an isothermal treatment such as TC9 and tc6 titanium alloy is often used.

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