Introduction

Two thermal gradient experiments were designed to generate a single sample with a range of thermal histories. The fisrt was a temperature gradient to represent different aging temperatures. The second is along the lines of Jominy End Quench Test to represent different quench or cooling rates. The following post is a short documentation of the initial tests.

High Throughput Aging Temperature Experiment

The sample geometry is a cylindrical rod with holes drilled to the center for 8-10 thermocouples. One end of the rod is inserted in a salt bath held at a constant temperature (hot end), and the other end is screwed into a cooling block which is cooled by a liquid chiller (cold end). The sample material was Al-6061 in the T6 condition. We expect there to be a range of mechanical properties and microstructures along the direction of the temperature gradient.

Sample Drawing (Dimensions in Inches) Aging Expt sample

Cooling Block Aging Expt cooling block

Setup Pictures

Aging Expt Test 01-02

Aging Expt Test 01-02-annotated

Aging Expt Test 01-01

Aging Expt Test 01-01-annotated

Aging Expt Test 01-Salt Set Temp

Aging Expt Test 01-Chiller Set Temp

Results

Aging Expt Test 01-TempVTime

In the temperature versus time plot a small drop in temperature was caused by the chiller being turned on. The increase in temperature after the initial settle time was because we kept increasing the salt bath temperature to get the temperature range closer to the desired between thermocouples 1 and 8. Thermocouples 1-8 were inserted in the holes closest to the hot end of the sample. This plot demonstrastes that the desired temperature gradient can be achieved.

High Throughput Quench Rate Experiment

The sample geometry here similarly is a cylindrical rod with 8-10 thermocouple holes; in this case they are not equally spaced. A pin is inserted in the top to hold the sample in place on the quenching rig. The quench rig was made to follow ASTM Standard A255 for a Jominy End Quench Test (everything but the sample dimensions were based on A255 for this experiment and the fact that we are using Al-6061 and not a steel alloy).

The sample was solution heat treated at for 1 hour and 45 minutes in an air furnace. The sample was quickly moved the quench rig. After quenching the sample will be aged at for 18 hours. Again, we expect a range of mechanical properties and microstructures along the direction of the quench gradient.

Sample Drawing (Dimensions in Inches) Quench Expt sample

Setup Picutres

DSC03708

DSC03712

DSC03712-annotated

DSC03716

DSC03713

DSC03713-annotated

DSC03722

DSC03722-annotated

DSC03719

Results

Quench Expt TempVTime

Quench Expt RateVPosition

Notice that Thermocouple 2 is missing in this experiment because it malfunctioned during the test. Cooling rate was calculated as the difference in temperature over time between and .

Discussion

When these experiments are coupled with structure-property characterization, they serve as a way to quickly explore thermal processes in new alloys. Critical to the high throughput nature of structure-property-processing relationships is using spherical indentation stress-strain curves to measure properties. This study on Al-6061 will be continued from here with structure (Optical, SEM, and/or TEM) and property (microindentation stress-strain curves) characterization. This general framework is applicable to a variety of materials.

Acknowledgements and Resources

  • Special thanks to Andrew Castillo, an undergraduate at Georgia Tech, who helped with the drawings and design.

  • A useful resource for Jominy End Quench Testing from the University of Cambridge can be found here: Jominy End Quench Flow Simulation