Does lanthanum has any effect on TZC alloy chemical composition of grain boundary?
Scanning Auger electron microprobe analysis shows that, without the addition of lanthanum (La) of the PM-TZC alloy, a large number of alloy elements carbon and oxygen impurity elements segregate at grain boundaries, such an analysis Segregation considered to be atomic state segregation, not to compound the state gathered at the grain boundaries.
Fig.1 is a non-lanthanum (La) of the PM-TZC alloy grain boundaries of the energy-and Auger electron Auger electron intensity diagram, the upper line in the figure is the original distribution of elements at the grain boundaries, which can be seen, in a large number of grain boundary segregation of carbon and oxygen, and the base body of Mo Auger peaks very low, the grain boundary covered by a number of impurity elements.
Fig.1 No Lanthanum (La) - TZC alloy Typical Fracture Surface Auger Electron Spectra
The bottom line in Fig.1 is two minutes atmosphere through fire-brigade ion distribution of elements, hydrogen ion sputtering peeling speed of about 400/min, so as to see the composition away from the grain boundaries, this time, carbon, and oxygen Auger peaks almost non-existent, while the matrix Mo Auger peak is very significant, indicating that the grain boundary impurity elements already covered kill shot off.
In addition lanthanum (La) alloys, carbon and oxygen segregation greatly reduced, Fig.2 containing lanthanum (La) 0.68% alloy fracture surface Auger electron spectra, the spectral figure on top grain boundary line is a distribution of elements, which can be seen that the top of the line in Fig.1 compared to the grain boundaries of the alloy, carbon and oxygen Auger peaks decreased, molybdenum substrate was Auger peaks increase, indicating lanthanum (La) could decrease the grain boundary segregation of carbon and oxygen, the bottom line in Fig.2 is the electron beams on the grain boundary precipitates is obtained by Auger electron spectroscopy, the precipitate is front of the kind referred to La2Zr2O7 as the core, carbide precipitates attached above the symbiotic phase.
Fig.2 Plus Lanthanum (La) - TZC alloy Typical Fracture Surface Auger Electron Spectra
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