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Results showed the presence of high tensile residual stresses at and near the surface of both titanium and Inconel alloys samples , whereas compressive residual stresses were seen at the center region .
 tensile residual stresses, surface, titanium, Inconel alloys, residual stresses
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:
 tensile residual stresses, surface, titanium, Inconel alloys, residual stresses