Development trend of heat treatment process for metal materials for aerospace

 In order to meet the comprehensive performance requirements of aerospace components, in addition to alloying design, micro structural control through heat treatment is a key step to achieve its performance potential and meet application requirements. For a specific aerospace device, a specific heat treatment process is required.

(1) Aluminum alloy

Combined with the thermal deformation process of aluminum alloy, the whole process control of grain structure and precipitation phase is an important direction for the development of aluminum alloy hot working process. Grain refinement and texture optimization through hot deformation processes such as rolling and extrusion are effective means for strengthening and toughening of aluminum alloy. The age-forming technology that combines creep and aging and simultaneously achieves forming and tissue control fits well with the comprehensive requirements for the overall, efficient and reliable manufacturing of complex panels, and is the preferred manufacturing technology for large aircraft-bearing siding. In addition, for the problem that large forgings are difficult to implement traditional aging, non-isothermal aging technology has been developed to ensure reliable handling of large-scale integral forgings such as aircraft tail beams.

(2) Titanium alloy

The evolution of microstructure of titanium alloy during thermal deformation and heat treatment is very complicated, and the difference of microstructure has a significant effect on the forming properties and serviceability of titanium alloy. Therefore, the heat treatment of titanium alloy is closely combined with the hot working process. . The development of key technologies such as near-state forging and equiaxed processing reflects the heat treatment idea of ​​integration of forming and organization control.

(3) Super alloy

The research on the hot working process of nickel-based super alloys mainly focuses on the δ phase forging and surface grain refining process. At present, the widely used heat treatment process is intermediately treated at 1050~1100 °C before aging treatment. The main effect of the intermediate treatment is to precipitate the γ film at the grain boundary to improve the grain boundary state. At the same time, some alloys also precipitate some γ phases with larger particles, which form a reasonable match with the fine γ phase precipitated during aging treatment.

(4) Ultra high strength steel

New technologies for improving the strength and toughness of ultra-high-strength steels are constantly evolving, mainly as follows: 1. Austenite processing: medium-temperature processing of metastable austenite before martensitic transformation. Deformed austenite with high dislocation density is inherited to martensite, increasing strength while maintaining toughness. Second, induced phase change: processing in the austenite-martensitic transformation process, deformation induced martensite transformation, improve strength and fracture toughness. Third, martensite processing: in the martensitic transformation, the processing of deformation to obtain fine martensite, together with the aging treatment to improve the strength of steel, and maintain a certain degree of toughness. 4. Recrystallization treatment: In the temperature range where solid solution is over and recrystallization does not start, fine-grained austenite is processed and deformed to transform into martensite with disordered orientation, fineness and shortness to improve strength. And resilience.

(5) Inter metallic compounds

For inter metallic compounds, how to achieve high elongation while maintaining strength is the goal pursued by material designers. For example, TiAl-based alloys are highly brittle at room temperature, and in view of the difficulty in obtaining fine-grained structures by conventional heat treatment methods, various new heat treatment processes of Ti Al alloys have been developed in recent years. One method is to introduce a high temperature beta phase into the TiAl alloy. The alloy is heated to the α+β phase region instead of the α single phase region, and the α grain growth is inhibited by β phase pinning, and then the cooling is controlled to finally control the grain size. One method is cyclic heat treatment to obtain fine equiaxed structure, fine-grained two-state structure and fine uniform full-layer structure

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