Transformation Plasticity in Steel Weld Metals

Professor Ulrich Dilthey’s passion for the science and technology of joining processes is amply reflected in the enormous archive of published work which will forever serve the community. It is a pleasure therefore to be able to present this small story as a tribute to someone who has been a scholar, a gentleman and a leader in this most difficult of subjects. The matter of our everyday world is made up of atoms and it is the behaviour of collections of these entities which governs the properties of macroscopic samples. The choreography of atomic motions during transformation is particularly important when dealing with martensite or bainite. These phases evolve by the synchronised movement of atoms, leading to visible displacements which can in principle be exploited to do work, a phenomenon intrinsic to the mechanical behaviour of TRIP– assisted steels. The subject of this paper is somewhat different, i.e., the control of the transformation strains to compensate for the contraction when a constrained welded component cools. We begin with a rigourous description of the deformation caused by the change of austenite into martensite or bainite.