title: High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies.
abstract: The ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni2TiAl/NiAl or single-Ni2TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxation behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200, USA.
authors.forename: Gian
authors.initials: G
authors.lastname: Song
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200, USA.
authors.forename: Zhiqian
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: Lujan Center, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
authors.forename: Bjørn
authors.initials: B
authors.lastname: Clausen
authors.affiliation: ISIS, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK.
authors.forename: Shu Yan
authors.initials: SY
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200, USA.|Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Yanfei
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200, USA.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Liaw