Impact of gamma' particle coarsening on the critical resolved shear stress of nickel-base superalloys with low aluminium and/or titanium content

TL;DR

This study models how gamma' particle coarsening in low Al/Ti Ni-base superalloys reduces their mechanical strength over time, specifically affecting the critical resolved shear stress at intermediate temperatures.

Contribution

It introduces a statistical model linking gamma' coarsening to changes in shear stress, providing quantitative predictions for alloy degradation.

Findings

Gamma' coarsening significantly reduces shear stress within a year.

The model predicts more than 50% reduction in gamma' hardening effect at 973 K.

Coarsening impacts mechanical properties critically over time.

Abstract

In Ni-base superalloys with low Al and/or Ti content the precipitation and subsequent coarsening of gamma' particles at intermediate temperatures contribute to the degradation of the mechanical properties of the alloy. In the present paper the coarsening process is modelled and the change of the critical resolved shear stress of the alloy due to coarsening of the gamma' particles is calculated by means of statistical analysis of the depinning of a single gliding edge dislocation. It is found that the contribution of gamma' hardening to the critical resolved shear stress at 973 K reduces to more than half of its original value in less than one year.