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Even though UAM has been demonstrated to produce robust metal builds in Al–Al , Al–Ti , Al-steel , Cu–Cu , Al–Cu , and other material systems , UAM welding of high strength steels has proven challenging .
 manufacturing process: UAM; material: metal; process characterization: builds; material: material; manufacturing process: UAM; machanical property: strength; material: steels
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: UAM; material: metal; process characterization: builds; material: material; manufacturing process: UAM; machanical property: strength; material: steels