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The fractured surfaces indicated a typical brittle mode of fracture with cleavages on the 420 stainless steel matrix whereas dimples and ridges were observed within the bronze phase .
 surfaces, brittle, fracture, 420 stainless steel, bronze
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:
 surfaces, brittle, fracture, 420 stainless steel, bronze