Influence of strain rate on the mechanical response of nanostructured coppers elaborated by SPD and SPS

François Barthélémy,Rémi Boulanger,Itamar Gutman,F Gálvez Díaz-Rubio,Florian Bussiere,Yuri Khoptiar,Hervé Couque,Foad Naimi,D.A Cendón Franco,Frédéric Bernard

doi:10.1051/epjconf/202125003014

Abstract

The influence of strain rate on the mechanical response of two different nanostructured pure coppers was investigated under uniaxial compression. The first nanostructured copper was elaborated by powder metallurgy using the Spark Plasma Sintering (SPS) process. The second nanostructured copper was elaborated by Severe Plastic Deformation (SPD). Conventional characterizations were conducted with quasi-static compression and tensile tests, hardness tests and, with microstructure analysis. The effect of strain rate was evaluated under uniaxial compression at strain rates varying from 10-4 to 10+4 s-1. The high strain rate data were generated with a direct Hopkinson impact technique. The increase of strength with strain rates was analysed and discussed from the Scanning Electron Microscope observations and grain size distribution. The mechanical properties are consequently dependent on the metallurgical history of these samples prepared according to two different routes.

Highlights

Many examples in the literature illustrate the specific characteristics of nanophased materials in electronics, magnetic recording, cosmetics, catalysis, etc. [1,2,3,4,5,6]
Some examples showed clearly that the improvement of mechanical properties of metals and alloys is historically related to a refinement of microstructure, since with a decreasing of the grain size the yield strength increases according to the Hall-Petch law [8,9,10]
This figure compares, for a dependence at a true strain 0.05, the behaviour of: (i) two samples prepared by Spark Plasma Sintering (SPS), CuSPS2 bi-structure (10 μm and 1 μm) without oxides and CuSPS3 bi-structure (10 μm and 1 μm) with oxides and (ii) two samples produced by Equal Channel Angular Pressing technique (ECAP), CuSPD1 non-recrystallized (1 μm) and CuSPD2 partially recrystallized with bi-structure composed of recrystallized grains of 20 μm and non-recrystallized grains (1 to 5 μm)

Summary

Introduction

Many examples in the literature illustrate the specific characteristics of nanophased materials in electronics, magnetic recording, cosmetics, catalysis, etc. [1,2,3,4,5,6]. Some examples showed clearly that the improvement of mechanical properties of metals and alloys is historically related to a refinement of microstructure, since with a decreasing of the grain size the yield strength increases according to the Hall-Petch law [8,9,10]. The combination of mechanical and electrical activations techniques involving fast heating rates has been recognized to be a suitable solution to produce dense nanostructured materials. Such approach has been optimized through the Spark Plasma Sintering (SPS) technique allowing the elaboration of dense metallic parts having a fine microstructure [12]. A microstructure analysis was performed in order to analyse such results

Material processing and microstructural analysis procedures

Mechanical characterisation data

Microstructural analysis procedures data

Strain rate influence on mechanical response

Conclusion