Kinetics of Engineering Materials

Experimental investigations of rate processes in engineering materials emphasizing the fundamental relationships between fundamental processes and the resulting microstructures.



TEM image of copper precipitates in an aluminum-copper alloy.

1. Heat Treatment of Aluminum Alloys, Precipitation Hardening
Aluminum alloys are strengthened primarily by precipitating many fine hard particles from a saturated "solid solution". In this experiment the students solution treat and age three aluminum alloys and observe the influence of time and temperature on peak hardness, the stages of the aging process and the effect of over-aging.

  • Procedure - Notes and the complete procedure for this experiment.

 

 

 

Back to top


The eutectoid structure of 1095 steel.  A small amount of proeutectoid cementite can be seen at the grain boundaries.

2. Heat Treatment of Steel, Eutectoid Systems
There are many ways to harden steel and the method used is based not only the desired hardness but also the desired strength, ductility, toughness and cost. In this experiment students learn which factors determine the maximum attainable hardness and the responsiveness of several steels to heat treatment. They heat treat the steels, hardness test them and examine their microstructures using the optical microscopes. From this one can begin to understand the basic reasons for the observed relationships between the heat treatments, the evolution of the microstructure and the mechanical properties.

  • Procedure - Notes and the complete procedure for this experiment.

 

 

Back to top


Large grains produced by annealing 70/30 brass for one hour at 750C.

3. Kinetics of Grain Growth
Many materials are polycrystalline and the size of these crystals (grains) can range from nanometers to inches. In this experiment the students anneal specimens of brass, examine the resulting microstructure using optical microscopes and measure the grain size using standard stereological techniques. The results are analyzed in terms of the ideal grain growth behavior and are discussed in terms of the role of the diffusivity of the copper and zinc in the brass.

Back to top


Jominy sample mounted in the hardness tester.

4. Hardenability of Steels
Hardenability is the ability to harden a steel at a given distance from the surface. If the steel has good hardenability it may be possible to get high hardness several inches into the material. In this experiment students anneal 1-inch diameter steel rods at over 900C then water quench them on only one end. The hardness is then measured every sixteenth of an inch or so from the quenched end and the distance where the hardness starts to fall off is noted. This is the classic Jominy End-Quench test. Using it the students learn that the carbon content in a steel determines its maximum hardness while it is the other alloying elements that determine its hardenability.

  • Procedure - Notes and the complete procedure for this experiment.

 

 

Back to top