Corelation between the microstructure, microhardness and corrosionresistance of Ti-5Al-2.5Fe

摘要

The electrochemical impedance spectroscopy (EIS) and the polarization techniquesrnhave been used to study the corrosion behaviour of different samples of Ti-5Al-2.5Fe afterrnundergoing specific heat treatments at 1025℃. The analysed alloy is a α + β alloy and containrna mixture of α (hexagonal close-packed structure) and β (body-centred cubic structure) phasesrnat room temperature. The microstructure of the titanium alloy is strongly influenced by thernprocessing history and heat treatment. The effect of cooling rate on the microstructure of Ti-rn5Al-2.5Fe annealed above the β transus was analysed and was found that as the cooling raternincreases, the lamellar hexagonal close-packed (hcp) crystal structure becomes finer. Thernmicrohardness of the titanium alloy (at 15 seconds, 200 grams) shows that there is arndifference of about 100 in the Vickers microhardness of the α and β phases and that thernmicrohardness of both of the phases increases with the increasing of the thermal treatmentrntime. The experimental results emphasised that the heat treatment, cooling rate,rnmicrostructure and microhardness, as well as corrosion behaviour, are strongly enhanced. Arnlong time heat treatment and a low cooling rate generate an homogeneous structure with highrncorrosion resistance and higher microhardness.