TC4 titanium alloy vacuum annealing process
TC4 titanium alloy contains 6% α stabilizing element and 4% β stabilizing element V, falling within the typical α + β type titanium alloy of Ti-Al-V series. The alloy account for about 40% of the market volume of titanium alloy series, cold processing is very difficult, mainly due to poor plasticity of the alloy, high yield ratio, and its mechanical properties and performance depends largely on the microstructure, the The microstructure mainly depends on the heat treatment process, so studying the different vacuum annealing process on the performance impact will play a decisive role in the subsequent processing. In addition, the study of different vacuum annealing de-hydrogen effect, the titanium alloy surface layer of hydrogen content reduced to a harmless concentration, eliminate the possibility of hydrogen embrittlement, to avoid the emergence of processing cracks is also necessary.
Sponge titanium, high purity aluminum (99.99%) and aluminum vanadium alloy by a certain percentage of melting in the vacuum consumable furnace. After forging, rolling into a semi-finished plate 3.7mm thick.
Heat processing heating temperature of 980 ~ 1020. It is found that the original β grain boundaries in the microstructure obtained by the thermal deformation of 95% deformation rate are very obvious, the α phase in the grain boundary is very obvious, and the α phase in the grain is arranged regularly in the form of coarse needles. The main reason for the formation of this structure is that the heating or deformation of the original billet is carried out in the β phase region or the original billet is carried out in the β phase region and the deformation amount is small when the α + β phase region is deformed. Grain boundary α is the grain boundary α phase due to lack of deformation left no recrystallization, this organization poor plasticity, high strength, it must be through the intermediate recrystallization annealing can improve its plasticity, reduce the intensity of cold deformation for the creation of good conditions . The observation also found that the grains in the zone of complete deformation are compact and obviously elongated.
The original 3.7mm sample was annealed in a vacuum annealing furnace, the selection of the plastic sheet properties of the worst specimens, takes 4 samples. Annealing system was 780 2, 800 2, 820 2, 830 2, the degree of vacuum 0.02Pa, incubated for 2 hours, baked at 200. After the determination of the room temperature tensile properties and hydrogen content. The results showed that:
(1) The annealing system is 800 2, holding 2 hours, can achieve lower yield strength and the highest plasticity.
(2) annealing system is 800 2. Heat 2 hours, can be stable α + β phase network structure.
(3) According to the vacuum degree of the existing vacuum furnace is less than or equal to 0.02 Pa, 800 ℃ ± 2 ℃ for 2 hours, the average hydrogen content is 0.009% lower than that of the original sample, and the hydrogen removing effect is obvious. Crisp levels of safety.
TC4 titanium alloy contains 6% α stabilizing element and 4% β stabilizing element V, falling within the typical α + β type titanium alloy of Ti-Al-V series. The alloy account for about 40% of the market volume of titanium alloy series, cold processing is very difficult, mainly due to poor plasticity of the alloy, high yield ratio, and its mechanical properties and performance depends largely on the microstructure, the The microstructure mainly depends on the heat treatment process, so studying the different vacuum annealing process on the performance impact will play a decisive role in the subsequent processing. In addition, the study of different vacuum annealing de-hydrogen effect, the titanium alloy surface layer of hydrogen content reduced to a harmless concentration, eliminate the possibility of hydrogen embrittlement, to avoid the emergence of processing cracks is also necessary.
Sponge titanium, high purity aluminum (99.99%) and aluminum vanadium alloy by a certain percentage of melting in the vacuum consumable furnace. After forging, rolling into a semi-finished plate 3.7mm thick.
Heat processing heating temperature of 980 ~ 1020. It is found that the original β grain boundaries in the microstructure obtained by the thermal deformation of 95% deformation rate are very obvious, the α phase in the grain boundary is very obvious, and the α phase in the grain is arranged regularly in the form of coarse needles. The main reason for the formation of this structure is that the heating or deformation of the original billet is carried out in the β phase region or the original billet is carried out in the β phase region and the deformation amount is small when the α + β phase region is deformed. Grain boundary α is the grain boundary α phase due to lack of deformation left no recrystallization, this organization poor plasticity, high strength, it must be through the intermediate recrystallization annealing can improve its plasticity, reduce the intensity of cold deformation for the creation of good conditions . The observation also found that the grains in the zone of complete deformation are compact and obviously elongated.
The original 3.7mm sample was annealed in a vacuum annealing furnace, the selection of the plastic sheet properties of the worst specimens, takes 4 samples. Annealing system was 780 2, 800 2, 820 2, 830 2, the degree of vacuum 0.02Pa, incubated for 2 hours, baked at 200. After the determination of the room temperature tensile properties and hydrogen content. The results showed that:
(1) The annealing system is 800 2, holding 2 hours, can achieve lower yield strength and the highest plasticity.
(2) annealing system is 800 2. Heat 2 hours, can be stable α + β phase network structure.
(3) According to the vacuum degree of the existing vacuum furnace is less than or equal to 0.02 Pa, 800 ℃ ± 2 ℃ for 2 hours, the average hydrogen content is 0.009% lower than that of the original sample, and the hydrogen removing effect is obvious. Crisp levels of safety.
