Influence of strain rate and Sn in solid solution on the grain refinement and crystalline defect density in severely deformed Cu

Abstract

A commercially pure Cu and a Cu-8wt.%Sn alloy were subjected to high pressure torsion (HPT) to study the effect of Sn as solute element and deformation rate on the grain refinement mechanism and the defect accumulation in Cu. The microstructure and hardness of produced ultrafine grained (UFG) states of both materials were carefully characterized. We show that addition of Sn in Cu leads to significant decrease in grain size, accumulation of higher stored energy and increase in hardness accompanied with the delay of hardness saturation with shear strain. Increasing HPT deformation rate induces significant heat dissipation in the processed materials markedly pronounced in CuSn8 as compared to Cu. Surprisingly, deformation rate has the opposite effect on the microhardness of UFG Cu and CuSn8, which decreases with the deformation rate for the case of Cu, while exhibits faster saturation to higher values for CuSn8. We also show that despite higher self-heating at higher deformation rates, higher HPT rotation speed provides reduction in grain size and increase in the defect density for CuSn8 alloy. This effect is assumed to be related to strong interactions between Sn solute atoms and strain-induced defects so that mechanically driven effects prevail over dynamic annihilation of dislocations. Finally, we present a qualitative model based on the phenomena of production and annihilation of dislocations. This model was able to reproduce the evolution of grain size, concentrations defects and hardness with different deformation parameters and after the addition of solute element in material.

Nanostructuring of Beryllium Bronze: Contribution of Grain Boundaries Segregation and Solid Solution

“…[12]. A higher Be content in solid solution likely reduces dislocation mobility with associated recovery processes, enhancing stability with grain size reduction through GB segregations [12]. This correlates well with the observation that despite inhomogemenius Be atoms redistribution and nonuniformed final grain size for Cu-1 wt.%Be, copper XRD peak have the same width as for homogeneous Cu-2 wt.%Be, i.e.…”

“…Microhardness of Cu -1 wt.% Be alloy after HPT sector processing, homogenization and subsequent room temperature HPT processing (b). [12]. A higher Be content in solid solution likely reduces dislocation mobility with associated recovery processes, enhancing stability with grain size reduction through GB segregations [12].…”

Effects of sintering aids on microstructure, mechanical, and optical properties of AlON ceramics synthesized by SPS

“…Moreover, with a decrease in grain size, the number of grain boundaries increases. Hence, more surface energy is required for crack propagation along the interface 60,61 . Third, the addition of La 2 O 3 increased the content of twin boundaries in the AlON ceramics by more than two times compared to that without the addition.…”

“…Hence, more surface energy is required for crack propagation along the interface. 60,61 Third, the addition of La 2 O 3 increased the content of twin boundaries in the AlON ceramics by more than two times compared to that without the addition. Figure 15 shows a micrograph of the crack propagation path on the AlON ceramic.…”

Influence of crystalline defects on nitrogen implantation in copper for surface hardening

“…Discs (20mm diameter, thickness 1mm) were deformed at room temperature under a pressure of 6GPa up to 20 rotations at a speed of one rotation per minute. A previously published work shows that it leads to ultrafine grained (UFG) structures with a high fraction of grain boundaries in both materials [19]. To obtain a reference material with a low amount of defects, a recrystallization treatment was carried out at 600°C during 1h giving rise to a grain size of about 50m.…”