The role of \b{eta} pockets resulting from Fe impurities in hydride formation in titanium

TL;DR

This study investigates how ta phase pockets caused by Fe impurities in titanium influence hydrogen trapping and hydride formation, affecting corrosion and failure mechanisms in titanium alloys.

Contribution

It reveals the role of ta pockets as hydrogen traps and their impact on hydride nucleation in titanium, highlighting impurity effects on material degradation.

Findings

ta pockets act as hydrogen traps.

Fe and H segregate at ta pockets.

ta pockets facilitate hydride growth along grain boundaries.

Abstract

The corrosion potential of commercially pure titanium in NaCl solutions is dramatically affected by trace Fe additions, which cause the appearance of submicron pockets of \b{eta} phase at grain boundary triple points. Furthermore, the low solubility of hydrogen in hexagonal close-packed {\alpha}-Ti makes titanium alloys prone to subsequent hydride-associated failures due to stress corrosion cracking. We analyzed {\alpha}-{\alpha} and {\alpha}-\b{eta} sections of the abutting grain boundary of a \b{eta} pocket in a Grade 2 CP-Ti, and the {\alpha}-\b{eta} phase boundary. Fe and H partition to \b{eta} and segregate at the grain boundary, but no segregation is seen at the {\alpha}-\b{eta} phase boundary. In contrast, a significant Ni (>1 at%) accumulation is observed at the {\alpha}-\b{eta} phase boundary. We propose that the \b{eta}-pockets act as hydrogen traps and facilitate the nucleation and growth of hydrides along grain boundaries in CP-Ti.