6668
Epitaxial growth of semi-circular and columnar δ ferrite grains accompanied by a marginal volume fraction of retained austenite and transformed martensitic phases was observed .
 machanical property: Epitaxial; material: ferrite; process parameter: volume fraction; material: retained austenite
Given options, please tell me the categories of all the listed entity words.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} 
 Entities: Epitaxial, ferrite, volume fraction, retained austenite 
Answer:
 machanical property: Epitaxial; material: ferrite; process parameter: volume fraction; material: retained austenite