The effect of annealing on the deformation behaviour and microstructure of crystallized Mg–23.5Ni (wt.%) alloy
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Rapidly solidified amorphous Mg–23.5Ni (wt.%) ribbons were crystallized at 300 and 400 °C for 90 min. After annealing at 300 °C the microstructure was heterogeneous, consisting of rounded eutectic–lamellar domains, which contained magnesium grains smaller than 500 nm. In the case of ribbons annealed at 400 °C the microstructure, however, was homogenous, and composed of well-formed magnesium grains and Mg2Ni particles. At room temperature both crystallized materials were brittle due to the high volume fraction of Mg2Ni particles, but they exhibited some ductility with increasing test temperature. Above 200 °C, the microstructure of the ribbons annealed at 300 °C was characterised by the formation of particle free zones during the tensile test. This structure was not observed in the material annealed at 400 °C. Deformation behaviour and changes in the microstructure during plastic flow of both crystallized materials were explained according to grain boundary sliding mechanisms.
KeywordsStress Exponent Grain Boundary Slide Annealed Material Pipe Diffusion True Strain Curve
M. Eddahbi thanks postdoctoral stage in Departamento de Física—Universidad Carlos III Madrid. The authors are grateful to MEC for financial support for this work under project MAT2003–02845.
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