There are holes in the titanium castings, which seriously affect the strength plasticity and fatigue strength of the castings. In order to improve and improve the performance of titanium castings and ensure the reliability of titanium castings, the following various processing processes can be used:
1, hot isostatic pressing
Hot isostatic pressing is to diffusely weld defects inside the casting under a certain high temperature and pressure, improve the coarse structure in the titanium casting, and improve the plasticity and fatigue strength of the titanium casting. Microstructure of ZT4 titanium alloy castings before and after hot isostatic pressing. Comparison of mechanical properties of titanium alloy castings before and after hot isostatic pressing. Because of this, in recent years, hot isostatic pressing technology has been adopted as a necessary process for producing high-quality titanium alloy castings for aerospace. With the wide application of hot isostatic pressing in titanium alloy castings, the application range of titanium alloy precision castings in space will be further expanded.
2, heat treatment
Altering the microstructure inside the alloy by heat treatment has been noticed in recent years. Although the microstructure of the two-phase titanium alloy casting is very stable in the α + β temperature range, as long as the heating temperature is close to or exceeds the β transition temperature, it can be subjected to β solid solution treatment, followed by medium speed or Quick cooling, or cyclic heat treatment, to obtain a low proportion of α phase, very fine flaky α and flaky α clusters, and even a basket-like structure, thereby greatly improving the high frequency fatigue performance of titanium alloy castings.
3. Thermochemical treatment
This is a new process developed in recent years. Its basic principle is to first dissolve about 3% of hydrogen in titanium alloy castings, form a eutectic alloy with titanium, and then perform various heat treatments on titanium alloy castings. Kimono hydrogenation results in a very fine microstructure that is completely different from the as-cast structure. Due to the improvement of the internal structure of the titanium rod and titanium alloy casting, the room temperature tensile strength plasticity reaches a level comparable to that of the deformed alloy. Therefore, it is a new process with great pioneering significance for casting titanium.
It is completely convincing that with the in-depth development of the above-mentioned series of research work, the current ideal problems in all aspects of titanium alloy precision casting technology will be solved, the production volume will increase rapidly, and the scope of use of titanium alloy precision castings will spread. Various sectors of industry, especially the civilian industry.