TA18 titanium alloy (Ti-3Al-2.5V), as a high-performance α-β titanium alloy, shows a wide range of applications in aerospace, ocean exploration and high-end medical devices due to its high strength, low density and excellent corrosion resistance. The purpose of this paper is to explore the influence of heat treatment process on the microstructure and yield strength of TA18 titanium alloy, with a view to providing theoretical basis and experimental support for the optimal application of this alloy. I. Heat treatment process of TA18 titanium alloy
As a key means to regulate the properties of TA18 titanium alloy, heat treatment can effectively improve its microstructure and mechanical properties by precisely controlling the temperature, time and cooling mode.
Annealing treatment
Purpose: Eliminate processing residual stress, improve the plasticity and toughness of the material.
Process parameters: temperature 700°C-800°C, holding time 1-2 hours, cooling with the furnace.
Effect: refine the grain, enhance the uniformity of the material, reduce the yield strength to about 450 MPa, increase the elongation to more than 25%.
Solid solution treatment
Purpose: To promote the uniform distribution of α-phase and β-phase, and enhance the strength and hardness of the material.
Process parameters: temperature 900°C-950°C, holding time 30-60 minutes, rapid water or air cooling.
Effect: The yield strength is increased to more than 800 MPa, and the tensile strength reaches 950 MPa, but the plasticity is slightly decreased.
Ageing treatment
Purpose: To further strengthen the material on the basis of solid solution treatment, and to improve the mechanical properties by precipitating fine sub-stable phases.
Process parameters: temperature 500 ° C - 600 ° C, holding time of 4-8 hours, cooling with the furnace.
Effect: yield strength of up to 900 MPa or more, tensile strength of about 1000 MPa, but plasticity is further reduced to about 10%.
Second, TA18 titanium alloy yield strength analysis
Yield strength as an important indicator to evaluate the plastic deformation ability of the material, by the heat treatment process is profoundly affected.
Untreated state: yield strength of about 620 MPa, tensile strength of about 780 MPa, elongation of about 20%, with good plasticity but low strength.
Annealed state: Through annealing treatment, the yield strength is reduced to about 450 MPa, accompanied by a significant increase in elongation, which enhances the plasticity and toughness of the material.
Solid solution state: Solid solution treatment significantly improves strength, with yield strength jumping to over 800 MPa, but at the expense of plasticity.
Ageing state: The aging treatment further strengthens the material, with the yield strength jumping to over 900 MPa, making it ideal for high-strength applications, but the plasticity is further reduced.
Experimental data and verification
In order to verify the above theoretical analysis, a series of experiments were carried out, and the specific data are as follows:
Annealing treatment experiment: temperature 750 ° C, insulation 1.5 hours, cooling with the furnace, measured yield strength 450 MPa, tensile strength 650 MPa, elongation 26%.
Solution treatment experiment: temperature 920 ° C, holding time 45 minutes, water cooling, measured yield strength 820 MPa, tensile strength 960 MPa, elongation 14%.
Ageing treatment experiment: temperature 550 ° C, holding time 6 hours, cooling with the furnace, measured yield strength 920 MPa, tensile strength 1020 MPa, elongation 12%.
IV. Conclusion
The heat treatment process of TA18 titanium alloy has a significant effect on its yield strength and comprehensive mechanical properties. By reasonably regulating the annealing, solution and aging treatment process parameters, an optimal balance of material strength and plasticity can be achieved to meet the needs of different engineering applications. Future research can further explore more refined heat treatment processes to fully exploit the potential of TA18 titanium alloy.
