title: Uncommon deformation mechanisms during fatigue-crack propagation in nanocrystalline alloys.
abstract: The irreversible damage at cracks during the fatigue of crystalline solids is well known. Here we report on in situ high-energy x-ray evidence of reversible fatigue behavior in a nanocrystalline NiFe alloy both in the plastic zone and around the crack tip. In the plastic zone, the deformation is fully recoverable as the crack propagates, and the plastic deformation invokes reversible interactions of dislocation and twinning in the nanograins. But around the crack tip lies a regime with reversible grain lattice reorientation promoted by a change of local stress state. These observations suggest unprecedented fatigue deformation mechanisms in nanostructured systems that are not addressed theoretically.
authors.affiliation: Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA. scheng.msg@gmail.com
authors.forename: Sheng
authors.initials: S
authors.lastname: Cheng
authors.forename: Soo Yeol
authors.initials: SY
authors.lastname: Lee
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Changhui
authors.initials: C
authors.lastname: Lei
authors.forename: Jon
authors.initials: J
authors.lastname: Almer
authors.forename: Xun-Li
authors.initials: XL
authors.lastname: Wang
authors.forename: Tamas
authors.initials: T
authors.lastname: Ungar
authors.forename: Yinmin
authors.initials: Y
authors.lastname: Wang
authors.forename: Peter K
authors.initials: PK
authors.lastname: Liaw