Though you won’t hear them referred to as such, aluminum knife handles are also alloys just like those made from zinc. The reason why is that aluminum is quite soft and stretchable in its natural state, characteristics that don’t make for durability. However, that changes once manufacturers add in other metals, most typically copper, manganese, silicon, magnesium, and/or zinc itself. Aluminum alloys generally outperform zinc alloys on every measure of strength, including tensile strength, yield strength, and hardness. (Note that this may vary with certain very specific kinds of alloys.)
When it comes to density, aluminum also outperforms zinc — in the opposite direction. Aluminum alloy is about half as dense as zinc, making it much, much lighter. This is the primary reason why many prefer aluminum over zinc from a performance perspective. Another is the fact that you can anodize aluminum, granting it a hard, protective layer by running the aluminum through an acid electrolyte bath with current passing through it. Anodizing also can lead to color or pattern changes, making it an attractive decorative option.
However, aluminum does possess some drawbacks. It’s susceptible to dings and scratches. It conducts ambient temperatures well, meaning it can get uncomfortably cold in cooler climates. It may prove hard to hold if not textured or covered (more on that below). And it’s significantly more expensive than zinc alloys.
In short, aluminum alloys enjoy greater strength, lighter weights, and more decorative options, but you can expect to pay for it.