This sounds like a typical material selection question, and I believe this type of question is fine, as long as you aren't asking for a recommendation of a particular manufacturer or product. Personally I would love to see more of this type of question as this is related to what I do.
Additionally, material selection falls under materials engineering, which falls under engineering. You should not, in my opinion, use the "mechanical engineering" tag for "materials engineering" specific questions, such as a material selection question, unless the question centers on selection of a material for a mechanical purpose. It is of course possible to use material selection principles for aesthetic, thermal, chemical, electrical, nuclear, and multi-domain applications as well.
In order to correctly select an optimal material, one must consider every aspect of the design, including shape, use case, loading, and environment. A material selection solution typically follows a rigorous quantitative process and can be quite involved for non-trivial applications. Even knowing what materials are available and what specific qualitative properties and idiosyncracies they have that may be beneficial or deleterious is not something that is developed except through experience and exposure to a wide array of materials or specialized material database software. It is also important to consider the effect of manufacturability and processing on costs. With all that in mind, it is important for a material selection question to include a lot of relevant information to get a high-quality answer.
