JaneDoH
Why didn't RR try diffusion bonded titanium fan blades?
The GE-4 which was designed for the failed SST program used wide-chord titanium compressor blades that were formed this way (it's effectively like glass blowing with hot metal) and it was pretty much as light as if it was a honeycomb blade except it wasn't. As far as I know the blades worked fine (the plane simply didn't)
The question is, how do you know (100% positively sure) the bond has been made? Perhaps today there is adequate inspection technology to survey the bonds and detect abnormalities now, but then inspection technology wasn't as advanced as today. The plane never got a chance to work, the contract (funding) by the US government was cancelled before any planes were built.
Turbine D