Abstract text (incl. figure legends and references)

The grain refinement can be described as a process of counterbalanced generation and annihilation (recovery, dynamic recrystallization) of dislocations during deformation. The stacking fault energy (SFE) or the solid solution hardening (SSH) contribution plays a decisive role and affects the grain refinement including the saturation grain size. [1, 2] The goal of this study is to investigate the solute effects on mechanical behavior, microstructure changes, and thermal stability in the Cu alloys after HPT processing at room temperature.

Cu and Cu alloys (CuSn5, CuZn5, CuZn30) were processed by severe plastic deformation (SPD) using a semi-constrained high-pressure torsion press under 4.5GPa. The isochronal heat treatment at different temperatures was applied to study the thermal stability of this alloy. Transmission electron microscopy (TEM) investigations indicated that dislocation wall structures are the main feature of Cu and Cu alloys after annealing treatment at different temperatures. Automated crystal orientation mapping (ACOM), which can provide full orientation maps with nanometer resolution, was used to test grain orientation, a fraction of high-angle grain boundaries, and mean grain size.

The grain growth kinetics in alloys are typically governed by the local elemental distribution e.g. the presence or absence of segregations (solute drag) or secondary phases (Zener drag). The Cu-X series remains single-phase upon annealing, indicating that the enhanced thermal stability of the alloys compared to pure Cu is related to the solute content, which provides dragging forces for grain boundary migration. A comparison of CuZn5 and CuZn30 indicates higher microstructural stability for CuZn5, as CuZn5 shows a constant hardness up to 250°C where CuZn30 has already started to soften significantly.

[1] Mohamed, F.A. and Dheda, S.S., On the minimum grain size obtainable by high-pressure torsion. Materials Science and Engineering: A, 2012. 558: p. 59-63 DOI: 10.1016/j.msea.2012.07.066.

[2] Bruder, E., Braun, P., Rehman, H.u., Marceau, R.K.W., Taylor, A.S., Pippan, R., and Durst, K., Influence of solute effects on the saturation grain size and rate sensitivity in Cu-X alloys. Scripta Materialia, 2018. 144: p. 5-8 DOI: 10.1016/j.scriptamat.2017.09.031.