Effect of Heat Treatment Combined with an Alternating Magnetic Field on Microstructure and Mechanical Properties of a Ni
- PDF / 3,268,852 Bytes
- 14 Pages / 593.972 x 792 pts Page_size
- 90 Downloads / 222 Views
DUCTION
NI-BASED superalloys are widely applied in aero and industrial gas turbine engines owing to their high strength, excellent tensile, and fatigue strengths as well as their resistance to corrosive conditions at high temperatures. The excellent properties evidently depend on alloy composition and processing conditions during solidification and subsequent heat treatment. In general, as-cast superalloy components undergo a two-step heat treatment, i.e., solution and aging heat treatments. The
CHUANJUN LI is with the State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering, Shanghai University, Shanghai 200072, P.R. China and also with the Otto Schott Institute of Materials Research, Friedrich-SchillerUniversita¨t-Jena, 07743 Jena, Germany. Contact e-mail: [email protected] MARTIN SEYRING and MARKUS RETTENMAYR are with the Otto Schott Institute of Materials Research, Friedrich-Schiller-Universitt-Jena. XI LI, YUNBO ZHONG, and ZHONGMING REN are with the the State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering, Shanghai University. Contact e-mail: zmren@staff.shu.edu.cn Manuscript submitted September 4, 2018. Article published online February 12, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
former is used to dissolve non-equilibrium microstructural constituents and to reduce the chemical segregation[1,2] and the latter is adopted to adjust morphology, size, and distribution of c¢ precipitates in order to obtain an optimum mechanical performance.[3,4] It is well known that directionally solidified superalloys have a heterogeneous dendritic structure with a certain fraction of c/c¢ eutectic. During solidification, some alloying elements such as Cr, Co, Mo, W, and Re segregate into the dendrite cores, whereas others like Al, Ti, and Ta segregate into the interdendritic region. Structural heterogeneities and chemical segregation severely degrade the mechanical properties of superalloys.[5,6] Therefore, it is necessary to dissolve the c/c¢ eutectic and to reduce chemical segregation as much as possible by a solution heat treatment. As a result, homogenization increases creep strength and ductility.[5] Additionally, coarse and incoherent c¢ precipitates in the interdendritic region have to be dissolved in the c matrix with the help of a solution heat treatment in order to afterwards re-precipitate fine, regular, and coherent c particles. Traditional heat treatment routines can achieve the qualitative aspects of the above goals, but some conflicts in the optimization of properties arise. One example is that higher solution temperatures improve the creep properties at the expense of reduced tensile and fatigue strengths.[7] Another example is that
VOLUME 50A, APRIL 2019—1837
the total content of heavy alloying elements (Ta, W, and Re) has continuously increased in recently developed single-crystal superalloys.[6] Although this increases stre
Data Loading...
