| Ti-6A1-4V alloy is the most widely used and most mature and has a good comprehensive performance of (α+β) two-phase alloys. Small size bar (Φ5-Φ30mm) of Ti-6A1-4V alloys are widely used in Aerospace, Marine, Electric power, Chemical industry, Medicine and Health care, and many other fields. At present, the small size of Ti-6A1-4V alloy bars were more prepare by Two-roll or Three-roll rolling, forging and drawing process.However, in the process of preparation, and the deformation for small, poor stability, low bar size precision, and the production efficiency is low.High speed wire rolling technology has a groove design precision, mill rigidity of the structure is stable, high-speed continuous rolling wa, can be used for producting Ti-6A1-4V alloy bars, solve the above problems.Therefore, this paper adopts the different high speed wire rolling processes prepared Φ10mm Ti-6A1-4V alloy bar, and conducted the different process of solid solution and aging treatment, the high speed wire rolling technology was studied and the heat treatment process on microstructure and properties of the alloy bars, obtain the following results:Ti-6A1-4V alloy though the high-speed rolling, the alloys strain hardening happen and dislocation interaction, raise the strength and hardness of the material.The initial rolling temperature usually choose under β phase transition point (930℃), the alloy bars were mainly composed of the primary equiaxial a phase and β phase, With the rolling temperature increased ,the equiaxial a phase was gradually reducing, while transformed β phase growing up and patchy distribution,the strength and hardness of the alloy bars were increased. However, the plastic of the alloy bars was decreased.The initial rolling temperature near phase transition point, the organization of the alloy bars were main layers of flake β transition organization, further increases in strength and hardness of the alloy bars, the elongation and the reduction of area of the alloy bars were decreased significantly, and then the mechanical properties can not satisfy with the relevant standard.High-speed rolling was applied to the preparation for small size bars of Ti-6Al-4V alloys, simplify the production process, improve the quality and improve the production efficiency, however, the strength of the alloy bars are lower by the High-speed rolling, in order to improve the rods strength, need to have different process of heat treatment on the alloy bars.The small size of Ti-6A1-4V alloy bars in annealing state is mainly composed of shaft between a and β phase composition, when the temperature at 930 ℃, the furnace cooling, air cooling and water cooling were used respectively to three kinds of solid solution, with the speeding up of the cooling rate, such as shaft a gradually disappear. The a phase grew up in the bar’s organization after furnace cooling, and a small amount of unstable β transformation in the bars organization after air cooling, the β transformation increased and uniform distribution when adopt quenching.Using quenching samples have respectively in different aging heat treatment process.Along with the aging temperature increaseed, the transformed β phase precipitated constantly a phase, and the micro structure of the alloy was consisted of the (a+P) phase and β phase. Meanwhile, the size of a phase growed up and then the microstructure became thick. Furthermore, the tensile strength of the alloy decreased and the elongation increased.Initial rolling temperature at 900℃, small size bar of Ti-6A1-4V alloys (Φ10mm) were prepared by High-speed rolling. Thro ugh the heat treatment of (930℃,30min,WQ)+(550℃,4h,AC) for this alloy bars were preferable of optimum mechanical properties, the tensile strength is 1031MPa and the elongation is 12.5%. |
PDF Full Text Request