Different alloys are created to provide different properties, so perhaps you should recast this differently. What, exactly do you want your material to do (what properties are important?) and the alloy might already exist for you to select from a materials handbook.
Your particular idea (iron, carbon, chromium, aluminum and titanium) is unlikely even today because the vastly differing properties of the materials, in particular aluminum. Aluminum has very different density than the iron, as well as different melting points etc. The inclusion of carbon (to make iron into steel) is usually done in minute amounts so the carbon can diffuse through the melt and the crystallization of the iron is affected by the presence of the carbon (generally no more than 2%). The addition of 10%+ chromium to the melt makes stainless steel.
I'm not entirely clear what the inclusion of aluminum will do to iron, (or for that matter, adding iron to aluminum mixtures), but since this does not seem to have been done to date, I suspect there is a reason for that.
WRT wanting to make a stronger steel structure, you can see that adding enough chromium to make stainless steel would probably make the steel skeleton prohibitively expensive. Carbon steel is much harder, but also more brittle, and can tend to rust quickly. Once specifications are made, metallurgists can start to experiment to create new formulations to meet the standard. Generally the state of the art will advance incrementally, in OTL the demand for strong, inexpensive and "tough" steel grew as more and more skyscrapers were being ordered (and this was due to a combination of land prices, the invention of the elevator and the prestige associated with tall buildings from the late 1800's to about the late 1960's). So the steel follows the demands rather than leads them.