Davies scored his first with a 70-meter dash after a brilliant interception in the 12th minute.
He then sent a baying crowd of 45, 000 at Lang Park into ecstasy by completing his treble with two more searing runs in a 10-minute burst after the break that knocked the wind out of the Blues and ensured the Reds would host next Saturday's final.
"Tonight was just unbelievable," said an elated Davies, the first Reds player to notch a hat trick of touchdowns. "The guys were scoring tries off our defense ... so I'm going to put that down to the forward.
"It's a great atmosphere (here) ... whoever we play we're going to be ready for." The Reds, who topped the table in the regular season, next face the Canterbury Crusaders or the Stormers who meet in Cape Town later on Saturday in the other semi-final.
Queensland continued their fairytale turnaround under coach Ewen McKenzie, who in two seasons has taken the team from the bottom of the southern hemisphere competition to one win shy of their first title in the tournament's professional era.
Although coming into the match full of steam after their crushing playoff win over the New South Wales Waratahs last week, the Blues were kept scoreless for 40 minutes before lock Chris Lowrey grabbed their only try.
A penalty goal from inside center Luke McAlister shortly after the break trimmed the deficit to 15-10 but the New Zealand side shot themselves in the foot with handling errors and were powerless to stop the surging red tide led by the marauding Quade Cooper.
Despite slotting only four of his eight kicks the Wallabies flyhalf was at his mesmerizing best, having a hand in three tries and booting a drop-goal five minutes from time.
The home side were given a flying start by Davies who pounced on an errant pass by fellow winger Lachie Munro and bolted 70 meters to plant the ball between the posts.
Cooper converted the try before setting up the second for the Reds with a breathtaking run that raised the roof.
After taking a clearing kick, the 22-year-old brushed away the hapless Munro with an arrogant fend-off, then charged down the right wing feinting two passes before slipping a ball to inside center Ben Tapuai who caught the ball by his bootlaces and crossed at the right corner.
"We were just having fun. Having fun with your mates is what it's all about," laughed Cooper.
He almost conjured a third for the Reds minutes later with another dashing run down the right, feeding Scott Higginbotham with an inside pass hurled from behind his back, but the flanker was stopped meters from the try line.
The Reds dropped their guard to allow Lowrey to cross under the posts after a 30-meter burst from the back of a ruck that cut the Reds defense to ribbons.
Any hopes of a concerted fight back were wrecked eight minutes after the break by Davies.
His second try, ducking inside to cross left of the posts, capped a brilliant maneuver that started with a lineout on the right before crossing the width of the field to punch a whole in the Blues defense.
Davies completed the rout out wide after receiving from outside center Anthony Faingaa before eluding three defenders on the touchline and planting the ball in the right corner.
Stunned, the Blues blew a chance to get within a converted try 10 minutes before fulltime when fullback Jared Payne spilled a pass meters from the left corner.
"We were able to put on some good pressure and then let them off the hook with some little mistakes and I guess a quality side like this over here in Brisbane — it's gonna work against you," said Blues captain Keven Mealamu.
"We threw everything we had at them ... we're just really gutted that we couldn't give the performance for all our fans at home."
