High entropy alloy composition

Sorry if this isn’t the right platform to ask this. So high entropy alloys usually contain elements in pretty much equal percentage. But in the research papers related to HEAs, some of the elements’ percentage is varied to see what effect it has. For example, in AlCoCrFeNi alloy, Al content is varied & the results are documented. In another paper about HfNbTaTiZr alloy, Ti content is varied. However, no exact reasons are mentioned as to why. What is the process behind selecting Al & Ti? Thanks in advance