Also many high-strength alloys, especially titanium products, are considerably difficult to form once the casting process is finished. The behavior of alloys in extreme environments is also an important factor. Many steel alloys tend to outgas some of their alloy elements when exposed to vacuum for example.
Taking all these factors into account, aluminum turns out to be the best choice metal material for extreme environment applications. Past and current aerospace applications clearly support this view.
Fiber-Metal composites share a very promising glimpse at the future of lightweight metal structures.