TY - JOUR
T1 - Deformation mechanism of Ni-based single crystal superalloy under ultrasonic surface rolling and subsequent thermal exposure
AU - Chen, Huitao
AU - Sun, Shouyi
AU - Tian, Fuzheng
AU - Dou, Min
AU - Liu, Lu
AU - Li, Lei
N1 - Publisher Copyright:
© 2024 Elsevier B.V.
PY - 2024/10/30
Y1 - 2024/10/30
N2 - In present work, ultrasonic surface rolling (USR) is applied to DD6 Ni-based single crystal (NBSC) superalloys, and the thermal relaxation behavior of the pre-treated alloys are investigated at 650 °C. Combined with mechanical properties, the plastic deformation and recovery mechanisms of the hardened layers are revealed in detail. Results show that compressive residual stress amplitude of 1163 MPa, 75.1 % improvement of surface nano-hardness and 83.02 % reduction on surface roughness are achieved by USR. Both deformed layer thickness and slip density progressively increases with USR cycles, where initial octahedron {111}<110> slips transform to a mixture of octahedron {111}<110> and dodecahedron {111}<112> slips. Meanwhile, shear step length expansions form γ′ segment/γ terminal interface with superlattice extrinsic stacking fault (SESF) on 1¯11, which may have inferior energy threshold for γ dislocation invasions than primary ones through shortening mean free path. Also, this drives γ′/γ solute mingling to induce tortuous interfaces. While dislocation proliferation dominates γ channel hardening, the γ′ hardening derives from planar fault strengthening and net system energy augmentation. During thermal exposure, surface integrities of USRed DD6 are strongly degraded, attributable to slip trace elimination and local γ′ coarsening. Thermal exposure further compels the γ dislocation to migrate towards γ′ segment across γ′ segment/γ terminal interface. Then, they are probably consumed to motivate solutes to phase boundary to reshape the γ′ morphologies through interface rearrangements under the assistance of γ dislocation network. The orientation transformation of SESF on 1¯11 to 010 and the mixture of SESF and superlattice intrinsic stacking fault on 1¯11 are thought to be possible manipulated mechanisms for γ′ coarsening, significant impairing the work hardening of alloy due to interfacial coherency deterioration. This paper could provide guidance for USR strengthening designs of NBSC.
AB - In present work, ultrasonic surface rolling (USR) is applied to DD6 Ni-based single crystal (NBSC) superalloys, and the thermal relaxation behavior of the pre-treated alloys are investigated at 650 °C. Combined with mechanical properties, the plastic deformation and recovery mechanisms of the hardened layers are revealed in detail. Results show that compressive residual stress amplitude of 1163 MPa, 75.1 % improvement of surface nano-hardness and 83.02 % reduction on surface roughness are achieved by USR. Both deformed layer thickness and slip density progressively increases with USR cycles, where initial octahedron {111}<110> slips transform to a mixture of octahedron {111}<110> and dodecahedron {111}<112> slips. Meanwhile, shear step length expansions form γ′ segment/γ terminal interface with superlattice extrinsic stacking fault (SESF) on 1¯11, which may have inferior energy threshold for γ dislocation invasions than primary ones through shortening mean free path. Also, this drives γ′/γ solute mingling to induce tortuous interfaces. While dislocation proliferation dominates γ channel hardening, the γ′ hardening derives from planar fault strengthening and net system energy augmentation. During thermal exposure, surface integrities of USRed DD6 are strongly degraded, attributable to slip trace elimination and local γ′ coarsening. Thermal exposure further compels the γ dislocation to migrate towards γ′ segment across γ′ segment/γ terminal interface. Then, they are probably consumed to motivate solutes to phase boundary to reshape the γ′ morphologies through interface rearrangements under the assistance of γ dislocation network. The orientation transformation of SESF on 1¯11 to 010 and the mixture of SESF and superlattice intrinsic stacking fault on 1¯11 are thought to be possible manipulated mechanisms for γ′ coarsening, significant impairing the work hardening of alloy due to interfacial coherency deterioration. This paper could provide guidance for USR strengthening designs of NBSC.
KW - DD6
KW - Local coarsening
KW - Shear step length
KW - Slip behavior
KW - Thermal exposure
KW - Ultrasonic surface rolling
UR - http://www.scopus.com/inward/record.url?scp=85204473232&partnerID=8YFLogxK
U2 - 10.1016/j.surfcoat.2024.131369
DO - 10.1016/j.surfcoat.2024.131369
M3 - 文章
AN - SCOPUS:85204473232
SN - 0257-8972
VL - 494
JO - Surface and Coatings Technology
JF - Surface and Coatings Technology
M1 - 131369
ER -