6947
Three different powders with increasing oxygen content were used to produce specimens and characterize its effect on microstructure and tensile properties before and after heat treatment .
 powders, oxygen, microstructure, tensile properties, heat treatment
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:
 powders, oxygen, microstructure, tensile properties, heat treatment