Mechanical Properties of Metals

The subject is introduced by a review of experimental techniques for characterising mechanical properties with emphasize on simple tensile testing. It is given an introduction to dislocation theory necessary for the understanding of the mechanical properties of metals based on their crystalline nature. In particular the structures of aluminium, and steel are considered as these are of great importance for our national industry. Accordingly the basic mechanisms of yield phenomena and deformation hardening are treated. Relations between the microstructure and the mechanical properties are handled based on simple dislocation models. Furthermore, basic physical metallurgical theories for fracture is examined and an introduction to fatigue is made.

Having completed this course the student should know how to: - Make simple assumptions and derive based on these the theoretical strength of an ideal crystal. - Explain how and why plastic deformation of metals occurs by dislocation glide. - Estimate cutting reactions and explain interactions between dislocations. - Calculate the distance between partial dislocations. - Explain how a Frank-Reead dislocation source act and calculate the critical stress to activate it. - Account for strengthening mechanisms due to work hardening, grain boundaries, alloying elements in solid solution or asparticles. - Derive the strength contribution from shearable and non-shearable particles. - Make simple assumptions and derive the theoretical fracture strength of an ideal crystal. - Account for and apply Griffiths theory about brittle fractures, simple fracture mechanics and a dislocation based model for ductile fractures. - Explain the difference between low and high cycle fatigue, Paris-Erdogans low for crack growth and give a physical metallurgical description of fatigue in single crystals. - Make simplifying assumptions and derive Orowans low for dislocation speed. - Determine the critical slp system and relate the critical resolved shear stress to the tensile stress in a tensile test of a single crystal. - Describe the various stages of the stress-strain curve resulting from a single crystal tensile test. - Carry out simple fracture mechanical calculations, discuss the transition from ductile to brittle fracture based on temperature, chemical composition, grain size etc. - Perform simple mathematical fatigue calculations, apply the Goodman diagram and calculate the lifetime from Miners rule. - Account for microstructure and slip activity during single crystal fatigue.

Lectures and exercises. Lectures are given in English if there are students from the International master programme. Expected time spent: Lectures: 56 hours. Exercises: 24 hours. Self study: 120 hours. 8 out of 12 exercises must be approved,.