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We performed X-ray computed tomography , optical microscopy , and scanning electron microscopy to observe the spatial distribution , size , and shape of micropores and reveal their formation and evolution mechanisms during the deposition and heat treatment of the WAAM 2319 Al alloys .
 X-ray computed tomography, optical microscopy, scanning electron microscopy, spatial distribution, evolution, deposition, heat treatment, WAAM, Al alloys
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 computed tomography, optical microscopy, scanning electron microscopy, spatial distribution, evolution, deposition, heat treatment, WAAM, Al alloys