Isothermal Transformations in Alkane Alloys

We show that it is possible to make mixed n -alkane samples to change isothermally from the ordered crystal state (Φ ord ) to the rotator state R. This isothermal transition has been observed in DSC and X-ray powder diffraction experiments, for all compositions in various binary systems, by maintaining mixed samples for a long time in the R state. Thermodynamic analysis of the isothermal data, which correspond to experimental EGC temperatures, results in a successful calculation of the [Φ ord + R] equilibrium temperatures. The thermodynamic interpretation and X-ray diffraction observations show that the phenomenon corresponds to diffusionless, or martensitic transitions, in metal alloys.