Study On In-situ Synthesized And Organizatioal Performance Of Ti-Al Compounds

The Ti-Al compounds were in-situ synthesized by friction stir processing (FSP) and rotational extrusion alloying (REA). The formation mechanism and organizational performance of Ti-Al compounds were studied via SEM and Micro-area X-ray diffraction. Main study results are as follows:The good uniformity of the Ti-Al compounds was successfully synthesized by FSP. The plastic deformation and greatest content of intermetallic in the rotation speed of 750r/min and low advancing speed (23.5mm/min), through the positive and negative processing of five times. The raw materials occurr significant phenomenon of plastic deformation and fragmentation by FSP. The original Ti particles were existed with spectively residual Ti particles, strips of Ti-Al compounds and particulate intermetallic compounds on friction stir region.The matrix can be efficiently strengthen with intermetallic compounds, and it is obviously increase of strengthen. The specimen outside region of tensile strength compared the friction stir processing center region of the specimen, the maximum strength can be reached 197MPa, and the extension rate of 19%, for 2.3 times and 38% after aluminum of FSP. The sample of friction stir region can be increased which are mainly the result of strengthening mechanisms by the second phase particles.The effect of heat treatment temperature on the microstructure of friction stir region is significantly. The sample area percentage content of intermetallic compounds increased when the holding time was constant with increase of heat treatment temperature. The highest content of Ti-Al compounds was synthesis with the experience of 600℃, 6h insulation, while cracking phenomenon was occurred. The tensile strength of alloying regional samples was decline after 6 hours heat treatment with 550℃.The formation mechanism of Ti-Al compounds was mainly based on diffusion reaction by FSP, and the Ti-Al compounds reaction were mainly through three stages, which mixing, plastic deformation and in-situ reactions, and the produce large amounts of plastic deformation stage of dislocation defects in-situ provide the basis for the realization of the reaction.According to principles of friction stir processing technology, and the Ti-Al compounds were synthesized by using self-develop rotational extrusion equipment. The Ti-Al compounds can be in-situ synthesized, and the product is Al3Ti phase intermetallic compound. The size of Al3Ti particle is about 500nm, and the matrix of aluminum presence a large number of dislocations, which are irregular arrangement of curly state. The average hardness of alloying product is 108HV, four times hardness of matrix.