Microstructure modifications by tensile deformation in Ti-Ni-Fe alloy

The origin of anomalous ductility in Ti-Ni alloy systems has been investigated by using Ti₅₀Ni₄₈Fe₂ with tensile tests at wide temperature range about 200 to 800 K and TEM observations. The advantage of the alloy used is that there is no decomposition during tensile test at elevated temperature. Tensile stress-strain curve is divided into three types. Below 400 K tensile deformation behavior relates to stess and or strain induced martensitic transformation. Between 400 and 700 K serration is observed in stress-strain curve, which is derived from the formation of various deformation twins with rather large twinning shear. Anomalous ductility is attribute to the formation of these twins and increment of slip system. Above 700 K necking take place during tensile test and only dislocations are seen in the deformed specimen. However, type of burgers vector dose not change with deformation temperature throughout the present study.