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The improvements in the mechanical properties after post heat-treatment are mainly due to the elimination of thermal stresses and the changes of microstructures .
 concept or principle: mechanical properties; manufacturing process: post heat-treatment; machanical property: thermal stresses; material: microstructures
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: 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:
 concept or principle: mechanical properties; manufacturing process: post heat-treatment; machanical property: thermal stresses; material: microstructures