Steady-state characteristics of fcc pure metals processed by severe plastic deformation: experiments and modelling

ABSTRACT

A series of experimental studies are carried out to investigate the steady-state microstructures and mechanical properties of Cu, Ni, and Al obtained by equal-channel angular pressing (ECAP) at homologous temperatures. Under 0.32T_m the steady-state grain sizes d_s of the three metals are below 1 μm, and dominated by dynamic recovery mechanism. Discontinuous dynamic recrystallization (DDRX) occurs in Cu and Ni processed by ECAP at 0.4T_m. The variation of dislocation density at 0.32T_m (ρ_Cu>ρ_Ni>ρ_Al) shows a dependence on stacking fault energy (SFE), and it is consistent with the change of kernel average misorientation (KAM) values (Cu > Ni > Al). The SFE not only influences the strain hardening capacity of metals but also the critical strain needed to get steady-state. In order to understand the relationship between SFE and d_s quantitatively, a steady-state grain size model based on the Mohamed’s dislocation model is proposed through considering dynamic recovery mechanisms. Two important factors temperature and SFE are involved in the model, and other parameters and constants are determined from our experimental data. The predictions of d_s by the model are compared with d_s obtained by experiments for five fcc pure metals (Au, Ag, Cu, Ni, and Al), and the characteristic and limitation of the model are discussed.

KEYWORDS:

• Severe plastic deformation
• steady-state grain size
• dislocation model
• stacking fault energy
• temperatures

Disclosure statement

No potential conflict of interest was reported by the authors.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

The authors gratefully acknowledge the support from the National key research and development programme [grant number 2016YFB0700404] and the Science Challenge Project [grant number TZ2016004].