Martensitic transformation occurring under the influence of applied stress may be regarded as an alternative mode of plastic deformation of the transforming phase. Transformation plasticity may arise both directly from the shape deformation that accompanies transformation and indirectly from the accommodation strains associated with the shape change. Stress-activated transformation and the associated transformation plasticity can have a pronounced effect on the properties and behavior of a range of engineering materials. For a soft, ductile parent material, the formation of a brittle transformation product may have deleterious effects on properties, as is the case with hydride embrittlement in hydride-forming metallic alloys. However, if the parent material is inherently brittle but designed to comprise or incorporate a metastable phase susceptible to stress-activated transformation, transformation plasticity may provide an effective mechanism for the relief of applied stress and lead to improved toughness. Such is the case with the range of transformation-toughened ceramics incorporating metastable tetragonal zirconia. That group of metastable austenitic steels known as TRIP steels derive an increase in strength from the transformation product and an improvement in toughness from the process of stress-activated martensitic transformation.
|Number of pages||12|
|Publication status||Published - 1 Dec 1988|