Experiment (1): Metallography

Experiment (1) Metallography

Objective (write your own version in the report)

The aim of this experiment is to introduce metallographic preparations techniques (grinding, polishing and etching) for microscopic investigations to get acquainted with the preparation of metallographic specimens and to gain hands-on experience.

Key Words

Generate your Abstract and line of thought using (some of) the following keywords (use others if possible):
Metallography: microstructure, phases, Material Structure identification: levels: macro-, micro-, ultra- & nano-, Specimen preparation: sectioning, mounting, grinding, polishing, etching, precautions, Grain morphology: factors affecting, grain size and shape.

Introduction

Discuss the following topics in correct language and organized flow of ideas within your introduction:
1. Definition: Metallography
2. Need for microstructural investigations: application in fracture mechanics (fractography), material selection, material history
3. Overview of levels of material structure investigations, used devices, material structure phenomena observed (e.g. dimples, cleavage facets, phases, dislocations, micro-void coalescence)
4. Brief overview of the needed preparation techniques (further details should appear under the procedures section)

Procedures

--Make sure to include sketches or images for the following in the report.
Optical Microscope
Mounting, Grinding and Polishing machines

The section has to include a complete description of the procedures: used devices and their complete specifications (pictures), magnification power, etching solution (composition/concentration), heat treatment specifications (temperature/time) if any.

Include full account for the experimental procedures, giving full account for specimen preparation techniques:
1. Sectioning
2. Mounting
3. Course (planar) grinding gradually from rough to fine grinding
4. Rough polishing
5. Fine polishing
6. Etching

Explain in details the need for the above steps, highlighting the precautions.

Results/Discussion

Required: A "neat" sketch for the microstructure

Use (ALL) the following questions to build your discussion in a correct language and organized flow of ideas 1. Describe the grain structure (refer to your textbook pages 128-129, 146,153)
2. What are the parameters affecting the grain structure? What are the types of grains?
3. Why do we need to maintain flat surface for the specimen during grinding?
4. What are the precautions that should be taken during the grinding stages?
5. Why is it necessary to wash the specimens immediately after etching?
6. With what to wash the specimen after etching? (water, alcohol or acetone?)
7. What is the function of the etching solution? and the importance of using the correct concentration and time?
8. Why do the grains appear in different color grades under the microscope, even for single phase materials?
9. Why do the grains boundaries appear darker than the grains themselves?

Further References/Images

--Use (some of) the following pictures (make sure to cite) and comment on them in your lab report

--The following sites and books contain useful information and images for several articles that we have encountered in this experiment. Make sure to check them.

Lab handouts.

Kalpakjian, Serope. Manufacturing Process for Engineering Materials. Addison Wesley, 3^rd Ed., 1997.

Smith, William F. . Principles of Materials Science and Engineering. McGraw Hill, 3^rd Ed., 1996.

Metallographic Specimen Preparation Basics¶¶¶¶¶ http://www.metallographic.com/Basics.htm

Specimen Preparation Equipment Company¶¶¶¶¶ http://www.metatechind.com/products.htm

Academic Page for a similar experiment¶¶¶ http://compfab.me.lsu.edu/me3701/experiments/metallography/expt3.htm

Specimen Preparation Equipment in NASA¶¶ http://arioch.gsfc.nasa.gov/313/html/1-2-3.html

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