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It is urgent to develop new copper alloys for future fusion reactors (e.g. DEMO and CFETR). This work involved the design and fabrication of an alloy, Cu-0.8Cr-0.12Zr-(0.05Si), with increasing high-temperature softening resistance by thermo-mechanical treatment. The influence mechanism of Si on its mechanical properties and softening resistance at high temperature was investigated. The peak-aged Cu–Cr–Zr alloy containing Si exhibits higher ultimate tensile strength of 622 MPa, yield strength of 588 MPa with a considerable elongation of 17% and electrical conductivity of 76% IACS. The dislocation and Orowan strengthening trigged for finer Cr precipitates are proven to be the main reasons for the improvement in strength. Moreover, the increase in elongation originates from the deformation twins due to the lower stacking fault energy, as confirmed by the first principles. Meanwhile, the addition of Si can significantly improve the high-temperature softening resistance of the alloy. The main reason is that the growth of Cr precipitates is suppressed by adding Si, and its pinning effect on the boundary is better, thereby inhibiting the occurrence of recrystallization. [ABSTRACT FROM AUTHOR]

The CuCr 0.8 Zr 0.12 Si x (wt.%, x = 0, 0.02, 0.05 and 0.2) alloys were designed and prepared by casting method. The function mechanism of Si content on as-cast microstructure evolution and properties was revealed with the guidance of thermodynamic analysis and first-principles calculation. Cr 3 Si tends to form during solidification at higher Si content due to its relatively low excess Gibbs free energy, which was proven to significantly affect the mechanical properties of alloys. The relationship between microstructure and mechanical properties of as-cast CuCr 0.8 Zr 0.12 Si x alloy was also experimentally investigated. With Si content increasing from 0 to 0.2 wt%, the tensile strength and elongation of the CuCr 0.8 Zr 0.12 Si x alloys simultaneously increase from 251 MPa to 29.0% in CuCr 0.8 Zr 0.12 Si 0 to 268 MPa and 33.0% in CuCr 0.8 Zr 0.12 Si 0.05 , and then decrease to 229 MPa and 23.7% in CuCr 0.8 Zr 0.12 Si 0.2. Simultaneously, the electrical conductivity and hardness of CuCr 0.8 Zr 0.12 Si 0.05 respectively reach 57.2 %IACS and 85.1 HV, CuCr 0.8 Zr 0.12 Si 0.05 was thus identified to be the best composition with relatively high comprehensive properties in this case. • The microstructure and property of Cu–Cr–Zr alloy were optimized by Si addition. • The 0.05 wt% Si addition can lead to great grain refinement of Cu–Cr–Zr alloy. • Cr 3 Si phase tends to form with increasing Si content due to relatively low E G m i x l i q . • The interaction between Cr, Zr, Si atoms is most adequate when Si is 0.05 wt%. • The Cu-0.8Cr-0.12Zr-0.05Si alloy presents UTS of 268 MPa and 33% EL. [ABSTRACT FROM AUTHOR]