D.V. Shangina

Structure and Properties of Ultrafine-Grained Cu-Cr Alloys after High Pressure Torsion

The effect of chromium content (0.75, 9.85, 27%) and initial state on the thermal stability of copper-chromium alloys after severe plastic deformation has been studied by microhardness and electrical resistivity measurements. The stability of the structures is established to depend on the initial state of the alloys and on the content of chromium phase. In the low-alloy bronze, quenching before HPT substantially increases the thermal stability of the alloy relative to that observed after annealing. The softening temperature increases with increasing chromium phase content and reaches 450°C for the alloy with 27% Cr.

Structure and Properties of Cu Alloys Alloying with Cr and Hf after Equal Channel Angular Pressing

Equal channel angular pressing (ECAP) results in grain-subgrain structure formation in Cu0.75 %Cr alloy with the average size of structure elements of 320 ± 73 nm Addition of hafnium into the Cu-Cr alloy leads to decrease of average size down to 225±82 nm and to increase of the high angle boundaries fraction from 40% to 53%. Microhardness of the Cu-0.7 %Cr-0.9 %Hf alloy is higher, than of the Cu-0.75 %Cr alloy, as after ECAP, so after heating when the aging processes occur in the temperature interval 400–550 °С. The strength in the tension tests of the Cu-0.7 %Cr-0.9 %Hf alloy after ECAP rises in 2.2 times compared with the quenched state. The aging leads to additional strength growth by 19%.

Aging processes in low-alloy bronzes after equal-channel angular pressing

In this work, the aging processes in the alloys Cu–0.7% Cr, Cu–0.9% Hf, and Cu–0.7% Cr–0.9% Hf after equal-channel angular pressing (ECAP) are studied. ECAP leads to the dispersion of grains/subgrains up to 200–250 nm in the Cu–0.7% Cr–0.9% Hf alloy. It is shown that the Cu5Hf particles upon aging lead to more considerable strengthening and improvement of thermal stability as compared to Cr particles. The combined alloying with Cr and Hf results in the maximum strength upon aging. The optimal aging conditions making it possible to obtain simultaneously high strength, plasticity, and electrical conductivity in the alloys under study are determined.