made of

(i) is made of alloy EI437 - This means that EI437 is the particular designation of one of many alloys, and this one was used to make the item.

(ii) is made of EI437 alloy - This means it's made of alloy, more specifically, alloy EI437. (iii) is made of an EI437 alloy - This means that there is a series of alloys called the EI437 series, and the item is made of one alloy out of this series. (iv) is made of an alloy EI437 - This suggests that the speaker is unclear about exactly what kind of alloy he is talking about. Means something like: It was made of some alloy or another, I think it was EI437. (v) is made of an alloy, EI437 - This means that EI437 is the name of one alloy out of many (vi) is made of the EI437 alloy - This means there is a particular alloy designated as EI437, and it was used to make the item. Means the same as "is made of alloy EI437" but it a context where you might be talking about different alloys and want to emphasize that EI437 was the particular alloy used. (vii) is made of the alloy EI437 - This sounds awkward but not unfamiliar. Understood to mean "is made of the EI437 alloy".