The High Temperature Of Tc18 Titanium Alloy Deformation And Creep Behavior Research

TCI8titanium alloy is a near-beta type titanium alloy, it used as force-bearing component of aircraft because of its high strength, high ductility, hardenability, weldability. TC18titanium alloy is generally processed by forging and isothermal forging, its micro structure and mechanical properties are very sensitive to deformation parameters, and alloy always working on stress condition, the creep deformation behavior and microstucture revolution impacts the safe use of the alloy. This paper studied about high temperature deformation behavior and creep behavior of TC18alloy,The results are as follows:(1) On the temperature of two-phase region, the true stress-strain curves have significantly soften characteristics due to the adiabatic temperature rise; on the temperature in the single-phase region and at high strain rates, alloy show discontinuous yield phenomenon, on this condition, the stain rate plays an important role.different activity energy show different deformation mechanism. The activation energies of α+β regime and β regime are288kJ/mol and137kJ/mol.(2) The processing maps of TC18alloy were established based on DMM, and the result indicate that instability regions increased while the true strain increased. Combined with the micro structure observations, the spheroidization of acicular alpha phase take place on the temperature of700℃～800℃, and beta recrystallization take place on the temperature of850～900℃. The sheerbands can be observed when T=700℃～750℃and strain rate was about0.1s-1～10s-1(3)the property processing conditions of TC18titanium alloy:the temperature of700℃～850℃, strain rate at0.01s-1～0.001s-1and temperature of850℃～950℃, strain rate at1s-1～10s-1. The instability domain of processing map is established:the temperature of700℃～750℃and strain rate was about0.1s-～10s-1(4) The creep experiment had be taken and the experiment data was analysed: the activity energy of TC18titanium alloy are:σ=200MPa,Q=123kJ/mol, σ=250MPa,Q=140kJ/mol, a=300MPa,Q=164kJ/mol;.The stress sensitive parameters are:T=400℃, σ=200MPa-250MPa, n=1.31,T=400℃, σ=250MPa-300MPa, n=2.20, T=400℃,σ=200MPa-250MPa, n=3.14, T=500℃,σ=200MPa-250MPa, n=5.24.(5) When T=400℃, σ=200MPa, dislocation slip holds a leading post in the creep of TC18titanium alloy; when T=400℃, σ=250MPa and σ=300MPa, dislocation slip and dislocation climb holds a leading post in the creep of TC18titanium alloy;When T=500℃, σ=200MPa, dislocation climb and grain boundary slide holds a leading post in the creep of TC18titanium alloy; when T=500℃,σ=250MPa and300MPa, dislocation climb holds a leading post in the creep of TC18titanium alloy.