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On the other hand , air-cooling heat treatment was found to homogenize the microstructure of the WAAM ship plate , causing a slight decrease in the hardness and tensile strength , while the water-quenching cycle led to the formation of acicular ferrite and intergranular pearlite , contributing to the improved mechanical properties of the part .
 heat treatment, microstructure, WAAM, hardness, tensile strength, led, ferrite, pearlite, mechanical properties
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:
 heat treatment, microstructure, WAAM, hardness, tensile strength, led, ferrite, pearlite, mechanical properties