Enhancing high-temperature strength and thermal stability of Cu-Cr-Zr via twin structure by cryogenic rolling

Cu-Cr-Zr alloy is a candidate material for the heat sink components of divertor in future fusion device, which is required for high strength and thermal stability simultaneously. In this study, the Cu-0.76Cr-0.23Zr (wt%) alloy is prepared through room temperature rolling-aging-liquid nitrogen rolling (LNR) to form fine precipitates and twin/matrix coexisting structures. Besides, room temperature rolling-aging (RTR) method is also adopted as the contrastive route. The results indicates that the twin boundary with an average width of 53 nm is achieved in LNR. The yield strength of LNR Cu-Cr-Zr are 638, 544, 414 and 213 MPa at 273, 473, 673 and 873 K, which are higher than those of RTR sample by 180, 139, 80 and 37 MPa, respectively. The higher strength is attributed to the high dislocation density and unique twin boundary. Then both kinds of samples are subjected to isothermal annealing at 500, 600, 700, 800 and 900 K for 1 h to study the softening behavior . The LNR sample always shows higher hardness than RTR sample. The high thermal stability is related to the newly formed precipitates (on twin boundaries), Σ9 boundaries and stair-rod dislocations during the annealing process . Besides, studies of static recrystallization behavior suggest that the low mobility of partial dislocations and the hindrance of twin boundaries to dislocation motion led to a high recrystallization activation energy of 111 kJ/mol for newly developed Cu-Cr-Zr alloy. These findings underline the important interplay among precipitates, twin structures, and mechanical properties, and offer a promising design strategy for developing Cu-Cr-Zr alloy suitable for high-temperature applications. • The CuCrZr alloy with twin/matrix structure is prepared by room temperature rolling-aging-liquid nitrogen rolling (LNR). • The LNR Cu-Cr-Zr present a high yield strength of 638, 544, 414 and 213 MPa at 273, 473, 673, 873 K, respectively. • After isothermal annealing, the LNR consistently exhibits higher hardness than the sample rolling at room temperature (RTR). • The interplay among dislocations, precipitates and twin structures increase the structure stability of LNR sample.