Experiment (3): Hypo-, Hyper- and Eutectic Alloys

Experiment (3) Eutectic, Hypo-eutectic & Hyper-eutectic alloys

Objective (write your own version in the report)

The aim of this experiment is to:
     1. Get acquainted with phase diagrams, invariant reactions, and phase transformations.
     2. Studying the effect of the invariant reactions on microstructure.
     3. Differentiating between eutectic, hypo-eutectic, and hyper-eutectic microstructures.

Key Words

Generate your Abstract and line of thought using (some of) the following keywords (use others if possible):
Solid Solution Alloys: Substitutional, interstitial, Phase diagrams: nomenclature (phases, phase diagram construction), Phase transformation: invariant reactions, Eutectic reaction: conditions, microstructure (hypo-, hyper- & eutectic)

Introduction

Discuss the following topics in correct language and organized flow of ideas within your introduction:
1. Definition: Phase diagram nomenclature (lines/phases)
2. Shapes of phase diagrams for different alloy systems (pure, extensive SSS, partial SSS, ISS and insoluble phases)
3. Invariant reactions
4. Significance of studying phase diagrams, invariant reactions, and other related issues.

Procedures

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

The specimen is made of an interstitial Cu-P binary alloy system. Three specimens with different phosphorus content (4.5%, 8.4%, 10.5%) were ground, polished, etched and prepared for microstructure investigations.
Specimen (1): 8.4% phosphorus content: etch or 30 seconds in aqueous ferrous chloride.
Specimen (2): 4.5% phosphorus content: etch or 40 seconds in aqueous ferrous chloride, which makes a dark surface after etching.
Specimen (3): 10.5% phosphorus content: etch for several seconds in a solution containing 2 parts of water/1 part ammonia solution and hydrogen peroxide.

Results/Discussion

Required: A "neat" sketch for the viewed microstructures. Describe the phase transformation for each specimen from the liquid state to the solid state with the aid of the following (Cu-Cu₃P)phase diagram.

Use (ALL) the following questions to build your discussion in a correct language and organized flow of ideas 1. Define the eutectic, hypo-& hyper- microstructures, giving full nomenclature for the composing phases.
2. Discuss the agreement between the theoretical eutectic microstructures and the viewed ones highlighting any shortcomings in the specimen preparation procedures if any.
3. Investigate various eutectic morphologies (review W. F. Smith, p.455)
4. Write the format of the eutectic reaction for the studied phase diagram

Further References/Images

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

Full Cu-P Phase Diagram Courtesy of Georgia Tech Phase Diagrams

[Figures by Moataz Attallah]

--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.

Georgia Tech Phase Diagrams Page

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)

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