I read up that aircraft compressor blades are generally made out of titanium. I was curious as to why is titanium the choice of material used for aircraft compressor blades? What alloys are involved and are there alternative materials used in the designing of such blades?
Have found a reference to "high grade steel" and to titanium. According to the (paper format) book, the parameter that dimensions the compressor is the perimeter speed (tip speed) of the blades $u_2$.
For steel: maximum $u_2$ = 450 m/s. With a total inlet entry temperature of 300 K, pressure ratio is 4.2
For titanium which has a higher strength/mass ratio: $u_2$ can be up to 500 m/s, leading to a pressure ratio of 6.
The book was written at the time of the B757/767 engines so there may be more modern materials around.
Also refer to this answer.
A more recent reference is provided by this presentation for the Trent 1000 engine:
- Fan and LP compressor blades are made from titanium alloy, containing small amounts of Fe, V, O, and Al.
- IP compressor: 8 stages of titanium blades.
- HP compressor: 6 stages of titanium blades.
The reason titanium is selected is that up to a certain temperature, titanium has the highest specific strength (strength/weight ratio), and in the compressor the temperatures stay below the transition temperature for nickel alloys:
Most famous one is Nimonic 263, which is 50% nickel and 20% Chrome and created with additions of Titanium and Aluminium. Used in Concord engines.