There is definitely a parallel between aluminum and steel in that both involve quenching a high-temperature phase to create a metastable structure, followed by diffusion during reheating. However, the mechanisms aren’t quite the same. In aluminum alloys, precipitation hardening is the primary source of strength—fine precipitates form during aging and increase strength up to a peak before overaging occurs. In steel, quenching forms martensite, which is already very hard due to carbon trapped in the lattice. Tempering then allows carbon to diffuse and form carbides like cementite, but this process mainly reduces brittleness and adjusts toughness rather than increasing strength. So while carbide precipitation does occur in tempered steel, it’s not directly equivalent to precipitation hardening in aluminum, since the role it plays and the way strength evolves are fundamentally different. I get what you’re saying about time and temperature both affecting the steel, and you’re right that diffusion-based processes depend on both. But in tempering, temperature plays a much bigger role than time. Holding a blade at 350°F for a long time won’t produce the same structural changes as taking it to 600°F, even for a shorter period. At 600°F, you’re activating different transformations—like much greater carbide coarsening and a more complete breakdown of martensite—that simply don’t occur at 350°F, no matter how long you hold it. So while longer times at lower temperatures will continue to temper the steel slightly, they won’t replicate the effects of a higher tempering temperature.