1398
Another reason for the poor commercial application of WAAM in aluminum is that some series of aluminum alloys , such as Al 7xxx and 6xxx , are challenging to weld due to turbulent melt pool and weld defects , which frequently occur during the deposition process .
 manufacturing process: WAAM; material: aluminum; material: aluminum alloys; material: as; material: Al; engineering feature: weld; material: melt pool; engineering feature: weld; concept or principle: defects; manufacturing process: deposition process
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: WAAM; material: aluminum; material: aluminum alloys; material: as; material: Al; engineering feature: weld; material: melt pool; engineering feature: weld; concept or principle: defects; manufacturing process: deposition process