Effect of heat treatment and boron addition on corrosion behavior of Ti-35Nb-7.2Zr-5.7Ta (wt%) ?-titanium alloy in simulated body fluid

Abstract

The corrosion behavior of Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys subjected to different heat treatment conditions was investigated in Hank's solution. Depending on the heat treatment conditions, the microstructure of the water-quenched, single-stage aged or duplex aged samples consists of very small amounts of ? or a precipitates in equiaxed � grains. Addition of boron to the TNZT alloy results in the formation of dispersed precipitates of titanium boride (TiB) in the � matrix. The other features present in the TNZTB alloy are similar to those in the TNZT alloy. Compared with single aging, duplex aging decreases the corrosion potential (Ecorr) and substantially decreases corrosion current density (icorr) and passive current density (ipass) values. Addition of boron to the TNZT alloy shifts the Ecorr value toward a more active direction and increases the icorr as well as ipass values significantly, and therefore deteriorates the corrosion resistance of the titanium alloys. In general, duplex aged TNZT samples show better corrosion resistance than other heattreated TNZT or TNZTB samples. � 2011, NACE International.