X-ray intensity decrease from absorption effects in mechanically milled systems
- North Carolina State Univ., Raleigh, NC (United States). Dept. of Materials Science and Engineering
Ball milling, i.e., mechanical attrition, has become a popular nonequilibrium processing technique to synthesize metastable materials such as amorphous or nanocrystalline structures. X-ray diffraction is often used as a major method to follow the evolution of the structural/compositional changes which occur during all milling of dissimilar powders, i.e., so-called mechanical alloying. Mechanical alloying (MA) can result in the formation of, for example, extended solid solubilities, metastable crystalline phases, nanocrystalline grain sizes, quasicrystalline, or amorphous phases. It has often been observed that during milling the x-ray diffraction lines of one of the components become anomalously weak or disappear. This may be attributed to the component going into solid solution in a crystalline solution of the majority phase or possibly to amorphization. However, in a number of experiments it was observed that the diffraction lines of the lower atomic number component disappeared or became very weak even though solid solution formation or amorphization were not occurring as determined by other techniques such as TEM. Understanding the evolution of the microstructure for mechanically milled immiscible systems provides insight into this phenomenon. By considering the microstructure for the mechanically milled Ge/Sn and Si/Sn systems, and by including x-ray absorption effects, decreased diffraction intensity can be quantitatively predicted for mechanically milled material systems containing strong and weak x-ray absorbers. The decrease in the diffraction intensity upon mixing materials with different linear absorption coefficients has been described by Klug and Alexander. The authors will quantitatively compare their diffraction results with the model of Klug and Alexander and extend the model to predict x-ray diffraction behavior in other weak/strong absorber systems.
- OSTI ID:
- 417801
- Journal Information:
- Scripta Materialia, Vol. 36, Issue 1; Other Information: PBD: 1 Jan 1997
- Country of Publication:
- United States
- Language:
- English
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