Abstract: A method of generating twin lamellas in a metal body includes the steps of introducing the metal body into a chamber, filling the chamber with a cooling medium having a temperature that will enable generation of twin lamellas in the metal body upon deformation thereof, and deforming the metal body while the latter is surrounded by the cooling medium. The cooling medium surrounds the metal body upon deformation of the latter is in a gaseous state. The present disclosure also relates to a device for generating twin lamellas in the metal body, the device including a chamber, a chamber inlet connected to a cooling medium source, and a deformation device arranged to deform the metal body. The deformation device is positioned inside the chamber so that the metal body will be surrounded by the cooling medium in a gaseous state while being deformed by the deformation device.