Why Carbon filament is elastic at room temperature and becomes plastic when heated by current? How to understand the phase transition from crystalline to amorphous ?
Every material except brittle materials undergo elastic to plastic deformation. It is a stimulus response kind of relationship. Current is a stimulus and at a certain magnitude of it strain is developed in the material at which material deforms (strain) to a magnitude called plastic limit which refers to onset of irrecoverable or irreversible deformation. Current energizes the material to such an extent beyond plastic limit by virtue of stretching and bending of bonds between the atoms to irretrievable degree. Below plastic limit the deformation is elastic which is reversible ulike plastic one. Crystalline to amorphous transition can be examined by characterizing the material using analytical techniques like XRD, microscopy etc.
It also probably has to be with the diffusion of defects in carbon at hight temperature. Defects are not statist, and the thermal energy provides a way towards defect migration towards more energetically favorable positions.
How do you know there is a crystalline-amorphous phase transition?
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