1504
It is reported that after ultrasonic impact treatment , the surface residual stress of WAAM-fabricated Ti6Al4V part can be reduced to 58 % and the microhardness can be increased by 28 % compared to the aB-fabricated sample .
 process characterization: ultrasonic impact treatment; concept or principle: surface; machanical property: residual stress; material: Ti6Al4V; material: be; concept or principle: microhardness; material: be; concept or principle: sample
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:
 process characterization: ultrasonic impact treatment; concept or principle: surface; machanical property: residual stress; material: Ti6Al4V; material: be; concept or principle: microhardness; material: be; concept or principle: sample