Solidification sensing using high-energy X-ray diffraction

A high-energy transmission X-ray diffraction technique that combines the capabilities of conventional high- and low-energy X-ray systems has been developed at the National Institute of Standards and Technology as a noncontact sensor for locating the liquid/solid boundary in metal castings. The high-energy (160 to 320 kV) X-rays can penetrate the thickness of most castings, as well as the mold and furnace walls. One practical goal for this new method is to collect data on the position, velocity, and possibly the shape of the solidification front of directionally solidified castings. Such information is vital for development and verification of improved solidification models, but it has been difficult to gather because of high temperatures, strong magnetic fields, and vacuum casting furnaces.