A thermodynamically consistent framework able to model both diffusive and displacive phase transitions is proposed. The first law of thermodynamics, the balance of linear momentum equation (in the linearized strain approximation) and the Cahn–Hilliard equation for solute mass conservation are the governing equations of the model, which is complemented by a suitable choice of the Helmholtz free energy and consistent boundary and initial conditions. To highlight thermo-chemo-mechanical interactions, some numerical tests are performed in which the phase transition is triggered by setting the value of the initial temperature; a time–temperature–transformation diagram is determined.