MICROSTRUCTURE OF HEAVILY DEFORMED MAGNESIUM-LITHIUM COMPOSITES CONTAINING STEEL FIBERS

The microstructure of deformation-processed metal-metal composites (DM MC) of Mg-Li alloys containing steel reinforcing fibers was characteri zed to correlate the fiber size to the deformation strain and mechanic al properties of the composite material, Micrographs taken using scann ing and transmission electron microscopy techniques revealed fiber siz es larger than predicted from the deformation applied to the bulk comp osite, Deformation strain in the fibers, therefore, was less than in t he bulk material. Measurements from SEM and TEM micrographs were used to calculate the actual deformation strain present in the fibers. This strain was then used to adjust rule-of-mixture (ROM) predictions of t he strength of the composite material. However, the experimental stren gths of these materials were still less than the adjusted ROM values, potentially due to the presence of fibers considerably larger than the average size measured stereologically. Of the many models used to des cribe the strengthening observed in DMMC materials, the Hall-Fetch rel ationship best describes the experimental data. Details of the strengt hening models are discussed in relation to these composite materials.