Abstract
The trade-off between strength and ductility has been an enormous difficulty in the field of materials for an extended time due to their inverse correlation.In this work,friction stir processing(FSP)was for the first time performed to high-strength and high-melting-point Ni-Co based superalloy(GH4068),and enhanced strength and ductility were achieved in FSP samples.At room temperature,the FSP sam-ple demonstrated significantly higher yield strength and ultimate tensile strength(1290 and 1670 MPa)than that of the base material(BM,758 and 904 MPa)and advanced wrought GH4068 alloy(982 and 1291 MPa),concurrent with high tensile ductility(～24％).Compared with the BM,70％higher yield strength of the FSP sample results from the remarkable contribution of grain-boundary and nanotwin strengthening,which has been confirmed by the multimechanistic model studied in this work.More im-portantly,with increasing temperature,an excellent strength-ductility synergy was obtained at 400℃,i.e.,the yield strength of the FSP sample was increased by more than 50％compared with the BM(from 789 to 1219 MPa);more interestingly,the elongation was also significantly increased from 17.9％in the BM to 28.5％in the FSP sample.Meanwhile,the Portevin-Le Chatelier effect was observed in the engi-neering stress-strain curve.The occurrence of this effect may be attributed to the interaction between solutes and defects like twins and mobile dislocations.Moreover,the grain refinement mechanism of FSP samples was proved to be discontinuous dynamic recrystallization.
基金项目
National Key R&D Pro-gram of China(2017YFA0700703)
National Key R&D Pro-gram of China(2019YFA0705300)
National Natural Science Foundation of China(11872354)
National Natural Science Foundation of China(11627803)
National Science and Technology Major Project(J2019-V-0006-0100)
Strategic Priority Re-search Program of the Chinese Academy of Sciences(XDB22040502)
NETL
NSTL
维普
万方数据