Analysing hysteresis and residual strains in thermal cycling curves of short fibre reinforced Mg-MMCs

Hysteresis and residual strains as exhibited by thermal cycling curves of QE22 based Mg alloy reinforced with Maftech®, Saffil® or Supertech® short fibres are analysed in order to interpret them correctly. It is found that parts of these arise from the instrument and therefore they do not have much meaning as such. The real permanent dimensional change in the material is imparted by plastic deformation of the matrix above 250–260 °C in the longitudinal direction and by release of residual compressive strain arising from the squeeze casting process above 195–205 °C in the transverse direction. This irreversible strain is measured by the deviation from the linear portion of the strain vs. temperature curves at higher temperatures. No microstructural change is observed on thermal cycling of metal matrix composites.