1421
For example , severe oxidization for titanium alloys , porosity for aluminum alloys , poor surface roughness in steel as well as severe deformation and cracks in bimetal components have been found to typically occur .
 material: titanium alloys; machanical property: porosity; material: aluminum alloys; machanical property: surface roughness; material: steel; material: as; material: as; concept or principle: deformation; machine or equipment: bimetal components
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:
 material: titanium alloys; machanical property: porosity; material: aluminum alloys; machanical property: surface roughness; material: steel; material: as; material: as; concept or principle: deformation; machine or equipment: bimetal components