7115
The variation of microhardness within the molten pool was ascribed to the number of grain boundaries and the stress characteristics of different kinds of microstructures under mechanical load .
 variation, microhardness, molten pool, grain boundaries, stress, microstructures, mechanical
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:
 variation, microhardness, molten pool, grain boundaries, stress, microstructures, mechanical