2131
Here we investigate the transient and spatial evolution of the fusion zone geometry , temperature gradients , and solidification growth rates during pulsed electron beam melting of the powder bed with a focus on the role of key physical phenomena .
 transient, evolution, fusion zone, temperature gradients, solidification, electron beam melting, powder bed
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:
 transient, evolution, fusion zone, temperature gradients, solidification, electron beam melting, powder bed