681
The heat treatment was conducted in the B2 + O ( HT1 ) and B2 + α2 + O ( HT2 ) phase field to obtain different microstructural characteristics .
 manufacturing process: heat treatment; material: O; material: O; concept or principle: phase; concept or principle: microstructural
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:
 manufacturing process: heat treatment; material: O; material: O; concept or principle: phase; concept or principle: microstructural