30131 - Mechanical Metallurgy M

Learning outcomes

The aim of this course is to illustrate the mechanical behaviour of metallic materials, under different service conditions. Starting from the basic relationship between microstructure and mechanical properties, the main metallurgical aspects influencing the static and fatigue resistance, the low and high temperature behaviour, as well as the wear resistance, will be presented and discussed. The effects of the production technique, including solidification conditions, plastic deformation, heat treatment or surface engineering modifications, will be evidenced. The characteristics of the main engineering metallic materials will be presented, including: iron-based alloys, aluminium and titanium alloys, metal matrix composites. By the end of this course one should have the ability to select the material and the processing conditions more suitable for the design and construction of reliable mechanical components.

Course contents

Requirements/Prior knowledge

A prior knowledge and understanding of basic knwoledge in Metals Science is required to attend with profit this course, normally obtained passing the Metallurgy T course in the Bachelor degree.

COURSE CONTENTS

Plastic deformation of metals. Plastic deformation by slip due to dislocation motion and by twinning. Effect of crystal structure on plasticity. Properties of dislocations.

Cold plastic deformation. Flow curve and strain hardening exponent. Effect of crystal structure and stacking-fault energy on strain hardening. Effect of cold working on microstructure and mechanical properties. Applications of the strain hardening mechanism.

Warm and hot working: recovery and recrystallization processes. Variables affecting recrystallization. Examples of application of recrystallization: Friction Stir Welding and Friction Stir Processing.

Short introduction to tradional and innovative production processes of steels.

Extra-low carbon steels for cold forming: Interstitial Free e Bake Hardening steels.

Carbon-manganese steels for structural applications and high strength low alloy steels (HSLA): chemical composition, production process, heat treatment and thermo-mechanical treatments, microstructure and mechanical properties, applications.

Multi-phase advanced high strength steels: Dual-Phase (DP) e Transformation Induced Plasticity (TRIP) steels.

Special steels for high mechanically loaded components: quenched and tempered, carburised, nitrided, carbonitrided and nitrocarburised. Springs and bearings steels. Tool steels. Bainitic steels. Maraging steels.

Stainless steels: ferritic, martensitic, austenitic, duplex and precipitation hardening.

Cast irons. Gray, spheroidal, compacted, austempered and white cast irons.

Fatigue. Main fatigue tests. The role of crystal structure and dislocation on fatigue failure. Metallurgical and mechanical aspects of fatigue. The role of solidification defectes, heat treatment and surface modification techniques on fatigue strength. A short introduction to linear elastic fracture mechanics: stress intensity factor and fracture toughness. Case studies on fatigue failed components.

Tribology. The theory of friction and its control. Processes and mechanisms of wear of main mechanical components. Selection criteria of materials and treatments to control friction and wear. Case studies on mechanical components subjected to tribological problems.

Cast and wrought aluminium alloys. Designation, alloying elements, strengthening mechanisms, heat treatments, properties and applications. Case studies on aluminium based mechanical components.

Titanium alloys and magnesium alloys. Designation, alloying elements, strengthening mechanisms, heat treatments, properties and applications.

Failure analysis. Fractography and Metallography.

Readings/Bibliography

Course Material (slides and notes) supplied by the teacher (available in the AMS Campus repository)

Specific references are reported at the end of the slides for each subject of the course.

Teaching methods

Lectures according to the timetable. Pratice in laboratory

Assessment methods

Achievements will be assessed by means of a final oral exam.

The oral session consists of 3 questions aimed to an analytical assessment of the "expected learning outcomes" described above.

To obtain a passing grade, students are required to demonstrate a knowledge of the key concepts of the subject and a comprehensible use of technical language.

A failing grade will be awarded if the student shows knowledge gaps in key-concepts of the subject and an inappropriate use of technical language.

Higher grades will be awarded to students who demonstrate an organic and deep understanding of the subject, a good capability of connecting different topics and a proper use of technical language.

Teaching tools

PC and projector, blackboard. Teaching lab (equipment for materialographic preparation; optical and stereo microscopy with image analyser; hardness testers; tensile tester).

Office hours

See the website of Lorella Ceschini