Experiment (2): Microstructural Identification

Experiment (2) Microstructural Identification

Objective (write your own version in the report)

1. Identifying the differences in microstructure between as-cast pure metals, and impure as-cast metals.
2. Pinpointing the characteristics of single phase (isomorphous) alloys versus 2 or more phase alloys.

Key Words

Generate your Abstract and line of thought using (some of) the following keywords (use others if possible):
Cast microstructure: effect of impurities, alloying elements, and heat transfer, Grain morphology: grain and grain boundary, Solidification: nucleationm crystallization and grain boundary formation, Nucleation: homogenous, heterogenous, impact on material properties.

Introduction

Discuss (some of) the following topics in correct language and organized flow of ideas within your introduction:
1. Factors controlling the solidifcation of pure metals and alloys
2. Solidification process: cooling curves, nucleation (heterogeneous or homogeneous), crystallization and grain formation
3. Grain boundaries: atomic mismatch
4. Conditions for forming SSS (full/partial), ISS, 2-phase alloys

Procedures

Include full details: magnification power, etching solution (composition/concentration), heat treatment specifications (temperature/time) if any.

Specimen:
1. Pure Zinc
2. Impure Zinc
both etched with a dilute HCl solution, 50% dilution

3. Copper-4% Tin Alloy
4. Al-4% Cu Alloy

Results/Discussion

Required: A "neat" sketch for the microstructure, indicating the specimen composition, etching solution & magnification power

Use (ALL) the following questions to build your discussion in a correct language and organized flow of ideas 1. Why is it difficult to differentiate between pure metals and extensive SS metals using microstructure?
2. What method can be used to differentiate between pure metals and SS metals?
3. Which is stronger: ISS, SSS, pure metal, 2-phase system for the same base metal?
4. What are the conditions for forming extensive (full) SS alloy and ISS?
5. What are the grain boundaries? and what is their effect on the mechanical properties?
6. What are the factors controlling the grain size?
7. What is the effect of different alloying elements (mechanical/physical/chemical)?

Further References/Images

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

[By Moataz Attallah] [After S. Kalpakjian] High Resolution [Ref. 2: Photomicrograph]

[After http://info.lu.farmingdale.edu/depts/met/met205/index.html]

--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.

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. (p. 128-132)

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

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