Why not use aluminum in drilling?

The need for more expensive, stronger drilling components can be satisfied by the use of aluminum-based alloys in drillstrings. Use of lighter drillstrings reduces maximum anticipated axial stress. Using aluminum for drillstrings and casing results in a 65% reduction in equivalent derrick loads, as compared to steel. Von Mises stress calculations show that required minimum yield strength for aluminum pipe is 52% less than for steel pipes. Aluminum pipe can buckle into a helix more easily than steel pipe. With no tension acting on the tubulars, internal yield strength of aluminum pipe is slightly less than steel pipe.