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The exception to this homogeneity occurs in the near-substrate region immediately adjacent to the pure Ti substrate used in these experiments , where the alloying process is not as well controlled as in the higher regions .
 material: Ti substrate; engineering feature: alloying; material: as; material: as
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: Ti substrate; engineering feature: alloying; material: as; material: as