On Shear Testing of Single Crystal Ni-Base Superalloys
- PDF / 2,229,193 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 94 Downloads / 182 Views
On Shear Testing of Single Crystal Ni-Base Superalloys G. EGGELER, N. WIECZOREK, F. FOX, S. BERGLUND, D. BU¨RGER, A. DLOUHY, P. WOLLGRAMM, K. NEUKING, J. SCHREUER, L. AGUDO JA´COME, S. GAO, A. HARTMAIER, and G. LAPLANCHE Shear testing can contribute to a better understanding of the plastic deformation of Ni-base superalloy single crystals. In the present study, shear testing is discussed with special emphasis placed on its strengths and weaknesses. Key mechanical and microstructural results which were obtained for the high-temperature (T 1000 C) and low-stress (s 200 MPa) creep regime are briefly reviewed. New 3D stereo STEM images of dislocation substructures which form during shear creep deformation in this regime are presented. It is then shown which new aspects need to be considered when performing double shear creep testing at lower temperatures (T < 800 C) and higher stresses (s > 600 MPa). In this creep regime, the macroscopic crystallographic [112](111) shear system deforms significantly faster than the [011](111) system. This represents direct mechanical evidence for a new planar fault nucleation scenario, which was recently suggested (Wu et al. in Acta Mater 144:642–655, 2018). The double shear creep specimen geometry inspired a micro-mechanical in-situ shear test specimen. Moreover, the in-situ SEM shear specimen can be FIB micro-machined from prior dendritic and interdendritic regions. Dendritic regions, which have a lower c¢ volume fraction, show a lower critical resolved shear stress. https://doi.org/10.1007/s11661-018-4726-9 The Author(s) 2018
I.
INTRODUCTION
SINGLE crystalline Ni-base superalloys (SX) are used for first-stage blades of gas turbines which have to withstand mechanical loads up to very high temperatures.[1,2] SX are heat-treated cast materials which represent technical single crystals, where the atoms of
G. EGGELER, N. WIECZOREK, F. FOX, S. BERGLUND, D. BU¨RGER, P. WOLLGRAMM, K. NEUKING, and G. LAPLANCHE are with the Institut fu¨r Werkstoffe, RuhrUniversita¨t Bochum, Universita¨tsstr. 150, 44801 Bochum, Germany and also with the Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universita¨t Bochum, Universita¨tsstr. 150, 44801 Bochum, Germany. Contact e-mail: [email protected] A. DLOUHY is with the Institute of Physics of Materials, ASCR, Zizkova 22, 61662 Brno, Czech Republic and also with the Interdisciplinary Centre for Advanced Materials Simulation, RuhrUniversita¨t Bochum. J. SCHREUER is with the Institut fu¨r Geowissenschaften, Ruhr-Universita¨t Bochum, Universittsstr. 150, 44801 Bochum, Germany and also with the Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universita¨t Bochum. L. AGUDO JA´COME is with the Bundesanstalt fu¨r Materialforschung und -pru¨fung (BAM), Abteilung fu¨r Werkstofftechnik, Unter den Eichen 87, 12205 Berlin, Germany. S. GAO and A. HARTMAIER are with the Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universita¨t Bochum. Manuscript submitted March 13, 2018.
METALLURGICAL AND MATERIALS TRANSAC
Data Loading...
