Abstract
The room-temperature strength of Mg-4 wt%Zn polycrystalline (grain size, about 50 μ) alloys at various aging stages was studied by the tensile test and electron microscopic observation. It was found that this alloy is age-hardened by the following mechanisms.(1) The yield strength in the early stages of aging (pre-β′) is determined by the increase of the energy which is required to make an interface dislocation between particles and the matrix due to the cutting of particles by dislocations.(2) The yield strength in the middle of aging (β′+β) is determined by the increase in energy of Mg·Zn pairs, which are put out of order by dislocations passing through the particles.(3) The yield strength in the stage of over-aging is due to the by-pass of dislocations on the basis of Orowan’s mechanism.(4) The work hardening in this alloy is explained by Ashby’s theory of secondary slip.
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