An alloy consist of a metal that is combined with other ingredients.
Often, the alloy is stronger and more resilient than the original metal. Thus, an alloy in a dream can represent the concept of the whole being stronger or more valuable than the individual parts.
If you dream about an alloy, your unconscious could be attempting to draw your attention to the importance of working together and communicating with others.
A dream about an alloy can be about the need for you to integrate different aspects of your personality.
If the alloy in your dream is weak, it can represent something in your waking life that is impure.