They now go forward to play New Zealand who accounted for South Africa on the 26-11 scoreline in the earlier semi-final.
The final is set for Hughenden on Sunday with a 4.15 kick-off.
Ireland:Andrew Finn (Dolphin); Richard Lane (UCC), John Hearty (Blackrock College), Glen Telford (Dungannon), Paul McKenzie (Loughborough University); Gareth Steenson (Queens University), Tomas O'Leary (Cork Constitution);John Wickham (Clontarf), Denis Fogarty (Cork Constitution), Declan Fitzpatrick (Belfast Harlequins); David Gannon captain (Blackrock College), Shane O'Connor (Cork Constitution), Brendan O'Connor (Cork Constitution), David O'Brien (Old Belvedere), Jamie Heaslip (Dublin University). Replacements: 16 Conor Geoghegan (UCD), 17 Keith Doyle (UCD), 18 Neil McComb (Dundee HSFP), 19 Oisin Hennessy (Dungannon), 20 Robbie Shaw (Wasps), 21 Michael Glancy (Loughborough University), 22 Breiffne O'Donnell (UL Bohemians).
Australia: 15 Drew Mitchell captain; 14 Henari Veratau, 13 Josh Graham, 12 Chris Siale, 11 Cameron Shepherd, 10 Daniel Halangahu, 9 Josh Valentine, 8 Mitch Chapman, 7 Lei Tomiki, 6 Rocky Elsom, 5 Alex Kanaar, 4 Simon Hockings, 3 Rodney Blake, 2 Steve Moore, 1 Hermon Hunt.Replacements: 16 Luke Holmes, 17 Greg Holmes, 18 Richard Brown, 19 Josh Fuimaono, 20 Luke Burgess, 21 Adam Ashley Cooper, 22 Chris Lyons.
Referee: - Bryce Lawrence (New Zealand)