Study of magnesium composites by neutron diffraction method
G.Farkas1,
K. Máthis1, Z. Száraz2
1Department of Physics of Materials,
2The University of Manchester, Oxford Road, Manchester M13
9PL, UK
farkasgr@gmail.com
Neutron diffraction has been applied to investigate lattice deformation and internal stresses in magnesium alloy Mg-5wt.%Al -1wt. %Sr (AJ51) reinforced with short Saffil® fibers Al2O3 with volume fraction 18% deformed in compression at room temperature. Lattice strain was calculated from position changes of diffraction peak {10.1} by using the Bragg equation.
The residual stress was measured with ex-situ neutron diffraction in the axial and radial direction with respect to the loading axis. It was found that in the matrix phase at initial state tensile residual stress is present in the matrix. In axial direction tensile residual stress evolution in matrix phase shows inverse behavior; it increases with applied compressive deformation. In radial direction the residual stress exhibits significant changes only at the beginning of deformation, during further deformation stays constant within the experimental error.
In-situ neutron diffraction was used for determining lattice strain in axial detector direction in samples with two different fiber orientations. The measurements revealed more intensive plastic deformation in the matrix for perpendicular fiber orientation, which is in agreement with the shear lag model [1], describing the load transfer from the matrix to the fibers.
The authors are grateful for
the financial support of the Czech Science Foundation under the contract
P108/12/J018. GF acknowledges the support from the
1. R. M. Aikin, L. Christodoulu, Scripta Metall.
Mater., 25, 1991, p. 9.