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Most of the research that has been done focused mostly on austenitic stainless steel grade , 316L and also on martensitic grade AISI 420 .
 concept or principle: research; material: austenitic stainless steel; machanical property: martensitic grade; material: AISI 420
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: research; material: austenitic stainless steel; machanical property: martensitic grade; material: AISI 420