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X-ray amorphous samples were obtained with laser power at and below 75 W. The aB-processed bulk metallic glass was found to devitrify by a two-stage crystallization process within which the presence of oxygen was concluded to play an essential role .
 X-ray, samples, laser power, metallic glass, crystallization, oxygen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 X-ray, samples, laser power, metallic glass, crystallization, oxygen