Precipitation Of Reinforcement Of Ti-2.5Cu Alloy And Its Effect On Deformation Mechanism And Mechanical Behaviors

The size, shape and orientation of particle in Ti-2.5Cu alloy were changed in different solution and aging treatment way, precipitated process of reinforcement phase was further researched, then mechanical behaviors and deformation mechanism of Ti-2.5Cu alloy reinforced by Ti₂Cu precipitates at different load modes were systematically studied. Finally, twinning deformation feature of α-titanium was analyzed and generalized. By analyzing interact between twin-twin, twin-reinforcement phase, twin-grain boundary, and reinforcement effect on twinning deformation process, appropriate reinforcement phase in titanium alloy was defined, combining with precipitates’ contribution on material strength to design a high strength and high plastic titanium alloy at low temperature. The results are as follows:The hardness value of Ti-2.5Cu alloy reinforced by Ti₂Cu precipitates is between 2000MPa and 2400MPa.Ti-2.5Cu alloy gained high strength and high plastic after monotonic tensile tests. But it achieved bad ductility, so it can’t use at impact work. At low -cycle fatigue behavior, the cycle hardness of Ti-2.5Cu alloy reinforced by Ti₂Cu precipitates is more remarkable. At high strain, the fatigue life is longer at low temperature than at room temperature, and these show its excellent plasticity.Ti-2.5Cu alloy reinforced by Ti₂Cu precipitates has good properties at 77K, which depends on its microstructure. Facture process of the material went through nucleation and growing and polymerization of the micropores. At 293K, dislocation slip is the dominant deformation mechanism, however, twinning shear is the dominant deformation mechanism at 77K. Three twins types were found at low-cycle fatigue tests at 77K, which were （112|-3）, （112|-1） and （112|-2）, the former are tensile twins, the later is compressive twins. It is worth noting that Ti₂Cu precipitates have two effects: one is that they hinder movement of dislocation and bring about obvious hardening; the other is that they have little effect on twinning process, whereas twinning can improve plasticity of Ti-2.5Cu alloy at cryogenic temperature due to twinning induced plasticity （TWIP）.Because twinning mechanism is very active inα-titanium alloy at low temperature, here, a way to design high strength and high plasticity materials was put forward: high strength would be achieved by situ growing intermetallic compounds, at the same time, plasticity of the material would be obtained by TWIP mechanism. So, more and more engineering materials with high strength and high plasticity would be obtained.