Role of structural parameters of ultra-fine grained Cu for its fatigue and crack growth behaviour

► High cycle fatigue and near threshold crack growth of HPT Cu were investigated. ► HPT materials show increased HCF life but also increased crack growth rates. ► Higher stability of commercial purity HPT Cu leads to superior HCF behaviour. ► High purity HPT Cu coarsens during fatigue loading and very slow crack growth. ► Bimodally structured HPT Cu has higher stability but no improvement in fatigue.