Effect of the Severe Plastic Deformation on the Corrosion Resistance of a Tantalum–Tungsten Alloy

Abstract

Tantalum and its alloys are regarded as equipment construction materials for processing aggressive acidic media due to their excellent properties. In this study, the influence of severe rolling (90%) on the dissolution rate of a cold-rolled Ta-4%W sheet in different directions was investigated during immersion testing and the corresponding mechanism was discussed. The results show that the dissolution rate of the cold-rolled sample is significantly lower than that of the undeformed sample. The corrosion resistance followed the sequence of “initial” < “90%-ND” < “90%-RD” < “90%-TD”, while the strength is in positive correlation with the corrosion resistance. Severe rolling promotes grain subdivision accompanied by long geometrically necessary boundaries and short incidental dislocation boundaries on two scales in the cold-rolled sample. The volume elements enclosed by geometrically necessary boundaries form preferential crystallographic orientations. Such preferential crystallographic orientations can greatly weaken the electrochemical process caused by adjacent volume elements, resulting in greatly reduced corrosion rates in the severely deformed sample. The unexpected finding provides a new idea for tailoring the structures of tantalum alloys to improve both their strength and corrosion resistance.

Investigating mechanical deformation’s role in cochlear implant durability

“…It was found that grain subdivision was caused by rolling, which resulted in texturization. As a result, electrochemical processes were weakened and corrosion rates were reduced in highly deformed samples [ 18 ]. In the work of Deng et al, the WE43 alloy also showed better corrosion resistance in the hot rolled specimens [ 17 ].…”

“…For instance the strength of the magnesium alloys WE43 is reported to increase as the rolling temperature increases, and tailored heat treatments result in improved corrosion resistance [ 17 ]. Other materials, such as cold rolled tantalum/tungsten alloys also show significantly less dissolution than the undeformed reference samples [ 18 ]. Thus, better understanding the microstructure-process-property relationship could be an avenue to enhance the long-term service behavior of platinum electrodes used in cochlear implants.…”

The effect of plastic strain and temperature on the corrosion resistance of the Al-5.6Zn-2Mg powder metallurgy alloy during hot upsetting

“…The study revealed that increasing plastic deformation leads to an increased acceptor density in the passive film, thicker space charge layers, a weakened resistance of the passive film, decreased Fe and Cr oxides, and heightened electrochemical dynamics, ultimately reducing the corrosion resistance of the alloy. Ma et al [16] investigated the corrosion resistance of cold-rolled Ta-4%W sheets in aggressive acidic conditions. Severe rolling decreased dissolution rates, connecting corrosion resistance with strength via grain subdivision and crystallographic orientations.…”

Corrosion and Mechanical Behavior of Metal Materials

“…The seismic vulnerability of an aging bridge system was obtained by considering the failure functions of several related components [23]. Crucial attention was paid to the effect of severe plastic deformation on the corrosion behavior of a tantalum-tungsten alloy [24]; the severely deformed crystallographic orientations in the tantalum-tungsten alloy could be greatly weakened by an electrochemical process and could reduce the corrosion rate. The pre-exposure SCC (PESCC) of a ZK60 alloy induced by preliminary immersion in a NaCl-containing solution was systematically studied in one paper [25], and it was argued that the hydrogen stored within the corrosion product layer and the corrosion solution was responsible for the formation of these two zones.…”