Dear Jazzo: Titanium can be made fairly hard. I have a set of drill bits that package said were titanium, but I am sure they are just plated or something. For aircraft, the wonderful thing about titanium is that when air friction at high speed heats it up a lot, it does not sag the way aluminum would. One undesirable thing about it for boats is that it is a bit brittle when very cold. I wonder if it will ever be used as girders in big buildings for that reason. I thought at one time magnesium would have very desirable uses in buildings, until I remembered seeing German WWII aircraft made of magnesium burn like gigantic Forth of July displays.