METALLOGRAPHY AND FAILURE ANALYSIS
Academic year and teacher
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- Versione italiana
- Academic year
- 2022/2023
- Teacher
- ANNALISA FORTINI
- Credits
- 6
- Didactic period
- Secondo Semestre
- SSD
- ING-IND/21
Training objectives
- Aim of the course is to initiate the students to the metallographic practice and to provide methods to understand the most important microstructures of ferrous alloys, according to production processes, heat treatments and supply conditions. The student will learn the potentiality of the well-established and advanced techniques for the characterization of metallic materials. Fundamentals of both non-destructive and destructive testing will be presented. The students will also learn to understand the micro and macro mechanisms involved in static, dynamic and fatigue failures.
Moreover, the methodological approach to the Failure Analysis as well as to the laboratory routine analysis will be presented.
The knowledge of these aspects is a key aspect in the working life of a mechanical engineer in both cases of the management of a metallurgical laboratory and the maintenance of industrial plants. Prerequisites
- The student must have the knowledge of the most important characteristics of ferrous alloys.
Course programme
- The programme of the course is divided in two parts:
1) Classroom-taught lessons on the following topics:
- Solidification of metals and alloys. Thermal and constitutional undercooling. Segregations.
- Metallographic techniques: macrograph and micrograph. Procedures for metallographic specimen preparation.
- Optical microscopy applied to metallography. Replica techniques in metallography. Quantitative metallographic techniques for measuring the grain size and to evaluate the non-metallic inclusions.
- Hardness tests and impact strength tests.
- Scanning electron microscopy (SEM). Microanalytical techniques (EDS and WDS).
- Failure Analysis techniques: methodological approach, case histories. Diagnosis of metallurgical defects.
- Non- destructive testing (NDT). Description and identification of the most important micro and macro mechanisms of fracture.
2) Laboratory experiences on the following topics:
- Metallographic practice: specimen preparation and specific critical issues. Bright field and dark field inspections, differential interference contrast and polarised light observations. Interpretation of microstructure and analysis of some of the most important alloys available for mechanical applications (plain carbon steels, low and high alloy steels, stainless steels, cast irons).
- Microstructural analysis of bulk and surface hardening treatments: hardness and microhardness testing.
- Fracture surface analysis of tensile, impact strength and fatigue samples: fractography by means of scanning electron microscopy (SEM) and EDS microanalysis.
- Application of image analysis techniques in ferrous alloys.
- Instrumented impact strength tests and interpretation of the results.
The normative aspects (UNI, EN, ISO and ASTM) are considered as a reference during the course. Didactic methods
- The course is arranged as follows:
- classroom-taught lessons on all the course’s topics;
- laboratory lessons concerning practical aspects of the course’s topics together with technical report of the practical activities. Learning assessment procedures
- The examination is oral and divided into open-answer questions.
The examination is aimed at evaluating the correct understanding of the theoretical subjects tackled during the frontal lectures. In particular, the ability to critically linking the different subjects covered during the course, rather than the capacity to simply repeat the specific topics, are evaluated.
Besides, the student has to demonstrate the understanding of the fundamental skills for the metallographic preparation and for the interpretation of the microstructure of studied metallic materials, in relation to production processes and heat treatments. Moreover, the ability to tackle failure analysis problems with an appropriate methodological approach will be evaluated.
Through the practical lessons, the student could reach a bonus of 2 points to add to the oral examination, provided that it is sufficient. Reference texts
- - Lesson notes and teacher’s handouts.
Textbooks for further study:
- B.L. Bramfitt e A.O. Benscoter, Metallographer’s guide – Practices and procedures for irons and steels, ASM International.
- E. Totten et al., Failure analysis of heat treated steel components, ASM International.
