Anisotropic behavior of tensile properties in a hot-extruded polycrystalline nickel-base superalloy
- PDF / 776,430 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 34 Downloads / 210 Views
Research Letter
Anisotropic behavior of tensile properties in a hot-extruded polycrystalline nickel-base superalloy Xiaotao Liu , State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083, China; National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Zaiwang Huang, State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083, China Liang Jiang, State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083, China; Institute for Advanced Studies in Precision Materials, Yantai University, Yantai, Shandong 264005, China Address all correspondence to Zaiwang Huang at [email protected] (Received 29 September 2019; accepted 22 October 2019)
Abstract The authors report an unexpected anisotropy in tensile properties of a polycrystalline nickel-base superalloy after hot extrusion. The tensile strength of longitudinal specimens (parallel to extrusion direction) is 170–276 MPa higher than that of the transverse counterparts at the temperature ranging from 25 to 750°C. Microstructural investigation excludes possible causes leading to this phenomenon such as variation in the grain size, texture, and γ′ precipitates in two orientations. However, further transmission electron microscopy observation reveals that plenty of twins uniquely exist in longitudinal tensile samples after deformation which are probably responsible for the mechanical gap between the two orientations.
Nickel-base superalloys manufactured by a powder metallurgical (P/M) technique have been widely used as turbine disk materials in the advanced aeroengine due to their excellent mechanical properties, i.e., extraordinary high-temperature strength, exceptional creep, and low cycle fatigue resistance.[1–7] Polycrystalline nickel-base superalloys possess a two-phase microstructure comprising the γ-phase (face-centered cubic) and the L12-type intermetallic γ′ precipitate.[6,8,9] It is commonly accepted that the mechanical strength of nickelbase superalloy is primarily determined by the grain size, in combination with the γ′ precipitate (geometry, size, distribution, and volume fraction).[4,9–13] In the past decades, substantial research work[5,7,13–17] has demonstrated that tensile strength and failure mechanism are closely associated with the working temperature and strain rate in nickel-base superalloys. Considering the isotropic nature of polycrystalline superalloy, the influence of specimen orientation on its mechanical behavior receives little attention in the community. As a result, few relevant papers have been published so far. In this report, we investigated the impact of specimen orientation on the tensile property of a polycrystalline nickel-base superalloy, after the accomplishment of hot extrusion processing. Two groups of tensile samples cut from the extruded superalloy ingot along with longitudinal and transverse directions were mechanically tested at elevated temperatures (25–750°C
Data Loading...
