Metallography

Objective:
To develop an understanding of the principles of practical metallography and the examination of some typical microstructures. Note: You will NOT be writing a lab report for this lab. Your lab notebook WILL be graded on the items in bold below:

Procedure:
Examine the specimens at different magnifications. Start with low power examination to obtain an overall picture. Then, at successively higher magnifications, resolve the fine detail. Draw a neat sketch of each specimen you examined at any suitable magnification. The sketch should include the magnification used.

Answer the following questions in your lab notebook PRIOR to coming to lab (this is part of the Pre-lab):

• What is the significance of microstructure in the material properties?
• Give examples of some microstructure-dependent material properties.
• What are the important steps metallographic sample preparation?

	SPECIMEN NO.	TYPE OF STRUCTURE
1)	X1	Pure Metal: Pure zinc, sand cast
2)	XlA	Impure Metal: Impure zinc, sand cast
3)	X2	Solid solution: Copper/4% Tin alloy, sand cast
4)	X5	Eutectic Type: Cu/8.4% P, eutectic alloy, sand cast
5)	X6	Hypoeutectic alloy: Cu/4.5% P, sand cast
6)	X9	Peritectic tvpe structure: Sn/10% Sb alloy, sand cast
7)	X10	Widmanstatten structure: Cu 58/ Zn 42, sand cast
8)	X17	Eutectoid reaction: 0.8 %C steel, 1 hr at 800 degrees C, furnace cooled (fully annealed)
9)	X18	Eutectoid reaction: 0.8% C steel, 1 hr at 800 degrees C, cooled in still air (normalized)
10)	X19	Hypoeutectoid steel: 0.35% C steel bar, furnace cooled from 870 degrees C.
11)	X20	Hvpereutectoid steel: 1.3% C steel bar, furnace cooled from 970 degrees C
12)	X25	Martensite: 0.35% C steel, water-quenched from 875 degrees C

Note: Specimens 8-12 will require the use of the oil immersion lens. Use the oil with the oil immersion lens only.

If the microstructure of a sample is not visible or the sample is bad, exchange the sample with one that is viewable. If a suitable sample is not found, ask the T.A. to assist you in polishing and etching the sample so that the microstructure is visible.

Before leaving the lab, have your T. A. examine and grade your lab notebook.

Go Back to Materials Science Main Page