Announcement of a computer program for the analysis of compositionally broadened X-ray diffraction peaks
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Communications Announcement of a Computer Program for the Analysis of Compositionally Broadened X-Ray Diffraction Peaks
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KARL E. WIEDEMANN and JALAIAH UNNAM Compositional broadening of X-ray diffraction peaks is the result of composition gradients in the diffracting material. When these gradients are normal to the surface of a flat specimen, composition-depth profiles can be calculated from a single diffraction peak using the program entitled "Transformation of an Intensity Band for the Analysis of Composition" or "TIBAC", which is available through the Computer Software Management and Information Center (COSMIC); ~documentation accompanying the program develops the underlying theories and describes the methods of solution. Compositionally broadened peaks are sometimes called intensity bands. They have been used in diffusion studies and other areas requiring high precision profiles. 2'3'4 Heretofore, the analysis of such peaks was a lengthy, trial-anderror process. Even with high-speed computers, analysis of a single band required days of the investigator's time. Due to the recent development of a direct solution, this analysis can now be done in minutes. The intensity band in Figure 1 is a compositionally broadened (002) oe-titanium peak. (The peak has also been broadened by the receiver slit, nonuniform strain, etc., but this will be corrected during the analysis.) The compositional broadening is the result of an oxygen gradient in the metal that d e v e l o p e d during o x i d a t i o n . Figure 2 is the composition-depth profile for the peak in Figure 1 obtained using "TIBAC." The time required to obtain the profile was 45 minutes: ten minutes for the peak scan, thirty minutes for manual data entry, and five minutes for computation. Of course, if an automated diffractometer with a serial interface had been available, then the manual data entry step could have been omitted and the time required would have been less. The profiles found by this method are very reproducible. For instance, in Figure 3 are the composition-depth profiles of two titanium specimens oxidized for 48 minutes at 704 ~ The symbols mark points selected at arbitrary intervals: circles for the first specimen and triangles for the second. The accuracy of this technique is demonstrated in Figure 4 where composition-depth profiles for the same specimen, which have been measured with microhardness and X-ray diffraction, agree within experimental error. Microhardness is known as a sensitive technique for determining composition in the titanium-oxygen systems'6 and has been used by investigators for constructing compositionKARL E. W I E D E M A N N , Materials Scientist, and JALAIAH UNNAM, Senior Scientist, are with Analytical Services & Materials, Inc., 28 Research Drive, Hampton, VA 23666. Manuscript submitted April 24, 1985. METALLURGICAL TRANSACTIONS A
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Fig. 1--Compositionally broadened (002) s-titanium diffraction peak. Broadening is the result of an
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