The
titanium alloy honeycomb sandwich structure named by the upper and lower panels and the middle honeycomb core by brazing method has excellent properties such as light mass, high specific strength and specific stiffness, noise elimination, heat insulation, shock absorption and energy absorption, etc. It is widely used in aircraft fuselage, rudder wing surface, engine cabin door, engine short square silencing liner and other parts. At present, titanium alloy honeycomb core is mainly applied layer by layer spot-welding. First, the titanium alloy sheets are rolled into the thickness of 0.05-0.1 mm, then the foil to the required size and specification of half-six-sided corrugated sheets. Finally, the half-six-sided corrugated sheets are baked and welded layer by layer, to produce the honeycomb core, which is a complicated process with a long production cycle.
Due to the above deficiencies in the current preparation process of titanium alloy honeycomb core system, inspired by the structural characteristics of lotus chamber in nature, a sandwich core with the structural characteristics of lotus chamber was proposed. The lotus chamber is independent from each other, only connected by lotus surface, showing typical hollow structure characteristics. According to the structure characteristics of the rosette, the column was formed on one side of the plate surface by vacuum hot spiraling method. At the same time, in order to further reduce the density of the core, vacuum thermal creep method was used to form the holes on both sides of the plate surface to form the double-sided characteristic core. Compared with the preparation process of titanium alloy honeycomb core system, plate can be directly used in the preparation process of lotus characteristic core system, and the core can be prepared in one step by vacuum thermal creep technology, which greatly simplifies the preparation process of sandwich structure core system.
Aiming at the idea of rosette characteristic core, an experimental study on vacuum thermal creep process of rosette characteristic core was carried out in TC4 titanium alloy. In the realization of the titanium alloy imitation of lotus seed pot sandwich core, on the basis of the preparation, using optical microscope (OM) and electron back scattering diffraction test results with electron backscattered diffraction (EBSD) characteristics of imitated lotus seed pot core microstructure were observed, the mechanical performance test equipment for flat crush strength of core body structure mechanics performance test, and analyze the main vacuum thermal creep into a form of process parameters on the core body height, the microstructure.
And mechanical properties. The results show that it is feasible to prepare the characteristic core of rosettes by vacuum thermal creep. During the process of vacuum thermal creep, the TC4 titanium alloy can realize the thermal forming of the core column by dislocation motion and grain boundary slip. After the vacuum thermal creep deformation, the microstructure changed completely from the original fine equiaxed structure to the recrystallized equiaxed structure. With the increase of forming pressure and holding time, the core height, flat compressive strength and specific flat compressive strength increase gradually.
