Effect of Hf Doping of Commercially Pure Copper on Evolution of its Microstructure under High Pressure Torsion

Evolution of the structure of commercially pure copper and Cu-0.8%Hf alloy under high pressure torsion (HPT) is compared. It is demonstrated that doping with Hf affects appreciably a tendency to relaxation processes inherent to copper. Introduction of additional impurities enables to achieve finer fragmentation of structure and increase of microhardness with the strain growth, compared to the commercially pure copper, in which these parameters are weakened by the intensively developing relaxation processes. However, these processes can serve a limiting factor for fragmentation and microhardness increase in the Cu-0.8Hf alloy as well, under the HPT by 5 revolutions of anvils.

Analysis of the Stress-Strained State of Billets Processed by Rotary Forging with Special Shape of the Tool

In this paper, we investigated the process of rotary forging of commercially pure copper grade M2 ​​using standard and special-shaped anvils and presented the results of studies obtained by the method of numerical and physical modeling. It is established that the use of anvils with special geometric shapes provides a higher level of accumulated strain and the formation of more dispersed structural states with the same elongation ratio under conditions of multi-cycle processing [1]. The formation of a finer structure in its turn increases the hardness and strength of the material. In addition, the special shape of the anvils provides a positive field of values ​​of the Lode-Nadai coefficient in the cross section of the samples, predominantly in a range of 0.3-0.7 and, correspondingly, a more "comfortable" stress state close to non-uniform all-round compression, which contributes to increasing technological plasticity.