1261
It is oversaturated with copper , like other alloys of the precipitation hardening 2 # # # series , which are used for structural applications in aviation .
 copper, alloys, precipitation hardening
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:
 copper, alloys, precipitation hardening