Effect of microstructure evolution of Ti6Al4V alloy on its cavitation erosion and corrosion resistance in artificial seawater

Abstract

• FC-TC4 and AC-TC4 alloys with more content of α phase were obtained by heat treatment. • Nano twins of TiV and TiAl 3 were formed separately in FC-TC4 and AC-TC4 alloys. • Refined recrystallized grain and more high-angle grain boundaries of AC-TC4 alloy enhanced its mechanical properties. • The passivating ability of AC-TC4 alloy was best among three samples because of its microstructure. • The cavitation erosion resistance of Ti6Al4V alloys in artificial seawater was closely related to their mechanical properties and passivating ability. The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application. On the basis of as-received Ti6Al4V(TC4) alloy, FC-TC4 and AC-TC4 alloys were prepared by heat treatment with the cooling method of a furnace and atmospheric environment, respectively. Then the microstructure evolutions of three samples were scrutinized and the effect of microstructure on their cavitation erosion and corrosion resistance was explored. The results showed that more recrystallized grains formed as well as its content of α grains and high-angle grain boundaries increased in AC-TC4 alloy. To FC-TC4 alloy, there was obvious grain growth apart from recrystallization. Moreover, many nanotwins of TiV and TiAl 3 were formed separately in FC-TC4 and AC-TC4 alloys due to the dislocation migration during heat treatment. The microstructure evolution led the hardness and elastic modulus of AC-TC4 alloy were the best, followed by FC-TC4 alloy, that of TC4 were the worst. Similarly, passivating ability of AC-TC4 alloy was the best among three samples because of its microstructure. Although cracks extended along the grain boundaries under the action of continual cavitation erosion, the passivation film formed by TiO 2 and Al 2 O 3 would enhance their resistance to further corrosion and cavitation erosion in artificial seawater.