High-temperature Oxidation Behavior And Tensile Property Analysis Of High Strength Titanium Alloys

Titanium and its alloys have been widely used in aerospace and other fields because of their excellent properties.The special requirements of titanium alloy application field part of titanium alloy needs to be used in high temperature conditions,with the increase of the use temperature,the high affinity between titanium and oxygen makes oxidation behavior in high temperature environment is difficult to avoid,but there is no completely isolated oxygen processing and use environment,alloy in the high temperature environment when used,Its oxidation resistance is the key to the long-term service of the alloy.This paper mainly studies the high-temperature air oxidation behavior of three titanium alloys at 600℃～800℃.By investigating the oxidation kinetics,the phase constituents and elemental distribution of the oxide films,the conclusions are as follows:The high temperature oxidation behavior and tensile properties of three titanium alloys were studied at 600℃～800℃.By means of X-ray diffraction(XRD),scanning electron microscope SEM)and energy dispersion spectrometer(EDS),the oxidation kinetics,phase composition and morphology of oxide film were characterized at different temperatures.The high temperature oxidation mechanism of the three alloys and the changes of tensile properties and fracture modes before and after oxidation were discussed and analyzed.The following conclusions are drawn:(1)The oxidation kinetics changed from cubic type to linear-parabolic type at 600℃～800℃of Ti5553 1 alloy and TC1 7 alloy,and the oxidation kinetics changed from linear-parabolic type to linear type of Ti555 1 1 alloy.The oxidation rate of the three alloys increases significantly with the increase of oxidation temperature.(2)For the specimens oxidated at 600℃ for 24 h,Ti55531 alloy and TC17 alloy oxide film is composed of single Ti3O,Ti55511 alloy oxide film is composed of Ti3O and TiO2;For the specimens oxidated at 600℃ for 24 h,the oxide films of the three alloys were composed of Ti3O and TiO2.For the specimens oxidated at 800℃ for 24 h,the oxide film of Ti55531 alloy is composed of Ti3O and TiO2,the oxide film of TC17 alloy and Ti55511 alloy is composed of Ti3O,TiO2 and Al2O3,and Titanium oxides of TiO2 and Ti3O grew at the interface between the oxide film and the matrix,while Al2O3 grew at the outer surface of the oxide film.(3)At 600℃～800℃,the tensile strength of Ti55531 alloy decreases by 40%and the elongation decreases from 7.5%to 1%.The tensile strength of TC17 alloy decreases by 68.6%and the elongation decreases from 6%to 0.5%.At 600℃～700℃,the tensile strength of Ti55511 alloy decreases by 24.8%,and the elongation decreases from 6.5%to 2.5%.This is because the brittle oxygen-rich layer formed on the surface of the sample is easy to induce fine cracks during oxidation,and changes the direction of crack propagation during the tensile process,thus causing the sample to fracture in advance.The oxygen-rich layer on the surface is one of the important reasons for the decrease in the elongation of the alloy after oxidation.