The United States and France adopt superplastic forming to process titanium foil heat insulation plates, 
However, the process can produce high-quality heat insulation panels, it has a long production cycle, the workpiece is in a high-temperature state for a long time, which will absorb oxygen more or less, Titanium no longer has antioxidant capacity above 649 ℃, it will absorb more oxygen and become brittle, resulting in the overall decline of its mechanical properties. In addition, superplastic forming is suitable for preparing workpieces with simple shapes. For the complex workpieces shown in Fig, superplastic forming is very difficult, because it is by no means easy to process molds.
Since the heat shield is made by diffusion welding, the oxygen content should be accurately and strictly controlled, so it is best to weld in the vacuum furnace, but it requires expensive equipment, which increases the investment and operation difficulty.
The researchers proposed that the qualified low-cost, high-quality, and high-efficiency titanium foil aircraft heat insulation panel was successfully prepared by using semi coupling die and cladding protection process. The effect was good and highly praised by users.
During production, TB2 alloy foil is first placed in the sheath, the oxygen in the sheath is removed before hot forming, which can be removed by the conventional vacuum pumping method, and the sheath is sealed after suction. The following matters shall be paid attention to when using jacketing Technology:
Carefully clean the greasy dirt and sundries on the surface of titanium sheet and package, and be sure to be clean;
Strictly select the cladding materials, which will not leak under high temperatures and will not emit any gas. Materials with low high-temperature strength should also be selected as far as possible, so as to reduce the deformation resistance, improve the service life of the die and ensure the dimensional accuracy of the workpiece；
A thin and uniform layer of flux stop shall be coated on the sheath to avoid welding between the sheath and titanium foil, but the flux stop shall not emit any harmful gas at high temperature and shall not contain substances such as water and glue.
The prepared sheath shall be formed at 750 ℃, the pressure shall not be too high, and it shall be preheated for 1min-2min, maintain the pressure for the 20s-30s, take out the package, and workpiece after it is cooled. The brightness of the workpiece surface is almost the same as that of the original foil. The measured results show that the oxygen content in the surface layer is less than 200 ppm, and the thickness of the oxide layer does not change. It can be seen that the cladding not only protects the workpiece from pollution but also undertakes most of the uneven deformation, which greatly improves the deformation uniformity of the workpiece, The measured thickness of the deformed workpiece is 0.067mm-0.072mm, which is completely within the thickness deviation range of the original foil.
