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It is also found addition of silicon in small amount ( 2.1 % –2.4 % ) effectively improves hardness , tensile strength and 0.2 % offset Yield Strength in comparison to pure copper‑aluminum alloy .
 material: silicon; machanical property: hardness; machanical property: tensile strength; concept or principle: offset; machanical property: Strength; material: alloy
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:
 material: silicon; machanical property: hardness; machanical property: tensile strength; concept or principle: offset; machanical property: Strength; material: alloy