X-rays have high energy and short wavelength when compared to visible light making them ideal for probing the interplanar distances in crystalline materials. Xstress X-ray diffractometers are engineered specifically to measure residual stress and retained austenite content unlike traditional powder XRD machines. Tailored Xstress X-ray diffractometers can measure various sample sizes and geometries, with little to no sample prep. Efficient measurement times yield significant benefits whether in the lab or on the production line.
X-ray diffractometer – X-ray production
X-rays are produced within an X-ray tube
- Heated filaments emit electrons by thermionic emission.
- Electrons are accelerated by a high voltage.
- Electrons hit a metal target and produce X-rays.
- Positively charged metal filament is heated with a high accelerating voltage (30 keV).
- Heat removes electrons from the filament.
- Electrons accelerate towards target material as an electron beam.
- Electron beam collides with the target material and removes an electron from the atom’s inner shell leaving a vacancy.
- Outer shell electrons drop in to fill the vacancy, emitting nearly monochromatic, characteristic X-rays (specific to the target material) in the process.
X-ray diffractometer – diffraction detection
Traditionally, 1-dimensional line detectors have been used in X-ray diffraction (XRD) residual stress and retained austenite measurements. With advances in detector technology 2-dimensional, or area, detectors can now be utilized in XRD measurements with the proven and standardized sin 2 ψ technique in both the modified χ and Ω orientations.
X-ray diffractometer – Measuring residual stress and retained austenite
First XRD machine exposures X-rays to part to be measured and detectors detect the diffraction. Residual stresses are calculated from the diffracted data by measuring the movement of the diffracted peak positions as the sample/XRD machine is tilted. Bragg’s law describes diffraction from crystallographic planes.
In retained austenite measurement the diffraction peak areas from different phases of steel are compared instead of determining the shifts in peak positions.