Iron Horse DW link rear pivot removal

 If the bolt is steel and goes into aluminium, you could wrap it all in rags and slowly pour a kettle of boiling water over it all. The alu will expand more than the steel, releasing the bolt a little. You may be able to unscrew the bolt with the hex or torx. If it is too rounded, you could drill a hole through the bolt and use an easy-out screw extractor tool and the kettle trick. It worked for me when the chain stay pivot bolt broke off in my frame. Unfortunately the kettle trick does not work if both are steel but the easy out might still work.