What is the heat treatment method for titanium alloy grade 5?

Heat treatment of titanium alloy Grade 5: annealing, quenching aging, chemical heat treatment. Annealing is used for various titanium alloys, including pure titanium and A-type titanium alloys
The only heat treatment method for gold is quenching aging: used for a+B, a+compounds, and metastable B-type titanium alloys.
Annealing: Relieve stress, improve plasticity, and stabilize the structure.
Process: Stress relief annealing, recrystallization annealing, double annealing, isothermal annealing, and vacuum dehydrogenation annealing, etc.
Stress relief annealing: eliminates internal stresses generated during processes such as cold deformation, casting, and welding. The annealing process is mainly
A response is required. The annealing temperature is generally between 450 and 650 ℃. The time required for stress relief annealing depends on the thickness of the workpiece and residual stress
Strength magnitude.
Complete annealing: eliminates work hardening, stabilizes the structure, and improves plasticity. This process mainly involves recrystallization
Called recrystallization annealing; At the same time, there are also changes in the composition, morphology, and quantity of phases a and Bm, most of which are a and a+B titanium alloys
All are used in a fully annealed state. The annealing temperature is between the recrystallization temperature and the phase transition temperature. If it exceeds the Ts point,
Deterioration of alloy properties due to the formation of coarse Weibull structure.
Type A and low concentration A+B alloys: The annealing temperature is 650-800C, and the cooling method is air cooling.
High concentration a+B-type alloy: It is necessary to control the cooling rate after annealing, as different cooling rates can affect the transformation of B-phase
By changing the method, the strength after air cooling is significantly higher than that after furnace cooling.
Unstable B-type alloy: The annealing temperature should be above 80-100 ° C TB, and fast cooling and slow cooling should be used to precipitate the a-phase,
Reduce plasticity.
Heat resistant titanium alloy: ensuring stable microstructure and properties under high temperature and long-term stress, with double annealing in Changchuan; The
Sub high temperature annealing is used to fully carry out recrystallization and control the number of primary alpha phases; The second low-temperature annealing is to bring the structure closer together
In a state of equilibrium.
A+B-type dielectric gold with high content of stable elements B: isothermal annealing is used, which results in high stability of the flash B-phase. Air cooling cannot make B stable
The phase is fully decomposed and isothermal cooling is used to completely transform the B phase.
Vacuum annealing is one of the main measures to eliminate hydrogen embrittlement, and the dissolution and precipitation process of radon in titanium is reversible. Therefore, it is possible
Using vacuum annealing method to reduce the hydrogen concentration in titanium. The annealing temperature is 650-680C, and the insulation time is 1-6 hours. The vacuum degree should not be lower than
1.33X10-1Pa.
Annealing process: After air cooling, needle shaped A precipitates on coarse B grains, which corresponds to higher fracture toughness and creep
Change resistance, but reduce room temperature plasticity.
The main difference in the strengthening mechanism between titanium alloys and steel is:
① The martensite obtained from steel quenching has high hardness and strong strengthening effect, while tempering softens the steel. And the martensitic hardness obtained by quenching titanium alloy
Not high, the strengthening effect is small, and tempering causes diffusion strengthening in titanium alloys.
② Steel has only one martensitic strengthening mechanism, while a+B-type titanium alloys with the same composition have two strengthening mechanisms: high-temperature quenching B-phase
The stable element B contained in it is less than the critical concentration, resulting in martensite. During aging, martensite decomposes and undergoes dispersion strengthening; Low temperature quenching
The stable element B in phase B is greater than the critical concentration, resulting in a metastable Bm+a ". After aging, the Bm phase decomposes into a dispersed phase
Alloy strengthening.
(2) Time effectiveness enhancement effect
It depends on the properties, concentration, and heat treatment specifications of the alloying elements. Because these factors will affect the formation of metastable phases
Structure, quantity, degree of decomposition, and dispersibility.
Under the same quenching and aging conditions, the strengthening effect of the same alloy system increases with the increase of alloy concentration. Usually at the critical concentration
Near Ck, the strengthening peak is reached, and corresponding to the Ck concentration, 100% metastable B-phase can be obtained by quenching the alloy, and B-phase undergoes aging process
The decomposition is also the most complete. Beyond the CK value, the stability of undercooled phase B increases, the degree of aging decomposition decreases, and the strengthening effect actually increases
Weakening.
Alloys with different compositions: The stronger the ability to stabilize the B-phase, the greater the aging strengthening effect. Simultaneous addition of multiple elements compared to a single one
The element strengthening effect is significant, in addition to time dispersion strengthening, there is also solid solution strengthening.
Alloy with a certain composition: The effect of aging strengthening depends on the selected heat treatment process, and the higher the quenching temperature, the better the aging strengthening effect