Mechanical behavior of a DD5 single crystal superalloy with different misorientations under quasi-static and dynamic com
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ARTICLE Mechanical behavior of a DD5 single crystal superalloy with different misorientations under quasi-static and dynamic compression Zhenpeng Liu, Hong Zhong,a) Yumin Wang, Shuangming Li, and Hengzhi Fu State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, People’s Republic of China (Received 31 January 2018; accepted 2 July 2018)
The effects of misorientation on the quasi-static and dynamic mechanical behaviors of a second generation Ni-based single crystal superalloy DD5 were investigated. A Split-Hopkinson pressure bar system was used to perform dynamic compression. The crystallographic misorientation between the stress axis and the [001] direction was characterized through rotating orientation X-ray diffraction. The results demonstrated that the flow stress was closely related to the misorientation. It decreased first and consequently increased as the misorientation increased from 0° to 45°. The dynamic flow stress was significantly higher than the quasi-static stress. Moreover, the flow stress under dynamics was more sensitive to the misorientation. A constitutive model was used to illustrate the misorientation effect on the mechanical behavior. Finally, the effect of strain rate on the crystal orientation was also investigated. It was discovered that the orientation deviation change following quasi-static compression could be neglected. By contrast, the orientation changed by 3–9° subsequently to dynamic compression.
I. INTRODUCTION
Nickel-based single crystal superalloys (SC-superalloys) have been widely utilized to gas turbine engine components, due to excellent strength and microstructure stability, as well as resistance to creep and fatigue at elevated temperatures.1–3 Compared to polycrystalline materials, the SC-superalloy presents noticeable microstructural and mechanical property anisotropy.4 Over the past years, many studies regarding the effect of crystallographic anisotropy on the mechanical properties of superalloys were conducted,5–10 combining theoretical calculations and experimental data. Earlier studies were mainly focused on the mechanical behaviors along the h001i, h011i, and h111i orientations. Certain alloys displayed the highest yield strength along the h111i orientation, such as the first generation PWA 1480 alloy at room temperature.9 Certain SC-superalloys displayed the highest yield strength along the h001i orientation, such as the SRR998 and CMSX-410 alloys. The mechanical property anisotropy could be affected by the SC-superalloy composition. Furthermore, the h001i-oriented single crystals are widely utilized due to their good mechanical properties at high temperature.11,12 A potential problem is, as turbine blades are produced with increasingly complex shapes, along with the addition of more heat resistant metal elements to improve the a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.251 J. Mater. Res., 2018
high temperature performance, the h001i orientation would be more diffic
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