NASA
&
The
University of Alabama in Huntsville, Center for Materials Research
These pages describe a new technique to directly observe the solidification (freezing) process in metal alloys in real-time by using x-rays. In the following pages you will find: images and explanations of what we can see, how it's done, and what we plan. Our method of X-ray Microscopy uses a special microfocus x-ray source to create images of the solid-liquid interface during solidification under controlled conditions. Features having dimensions below ten micrometers are being observed and studied in real-time. The information from this fundamental research is used to produce stronger alloys and composite materials. Every experiment is an exploration into previously unseen worlds.
The first example, above, shows the kind of fascinating internal structures we can observe. This is a medium magnification post-solidification x-ray micrograph of an aluminum-indium monotectic alloy unidirectionally solidified (from right to left) while the level of gravity was cycled up and down (along the long axis of the specimen) from 1.8 to 0.01 times earth gravity.
This was done by flying the furnace in a
NASA aircraft flown in a special, parabolic trajectory to simulate the low
gravity conditions in space for 20 seconds at a time.
The distribution of the indium particles that formed during the solidification are periodically clustered in bands according to the level of gravity imposed at that moment. (The specimen is 5 mm in diameter.) The X-ray Microscope is presently too large to fly in a microgravity environment but the XTM is used to examine flight samples before and after the experiments are run on the Shuttle or ISS. The true scientific value of the XTM is explore solidification phenomena as it happens in real-time. Examples of x-ray microscopy during solidification of aluminum alloys (in the laboratory) using the X-ray Transmission Microscope (XTM) can be found on the next page.
This work is being performed by Dr. William Kaukler at Marshall Space Flight Center in Huntsville, Alabama.
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What Can We Do? & Picture Gallery |
How to Do Hard X-Ray Microscopy: |
Planned Experiments & Publications |
Related Web Sites |
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one of these subject pointers below to continue...Last Updated October 5, 2006