The world number one continues her impeccable play, having dropped just 21 games in route to the final while striking 20 winners. She broke Keys four times while not being broken herself.
Barty will seek to become the first Australian woman to win her home Slam since Chris O'Neil in 1978 when she faces 27th seed Danielle Collins in Saturday's championship match.
Another dominant effort from world number one as Barty coasts into final
Barty continued her excellent play with a break in the opening game of the match, a forehand winner setting up the chance and a mid-court winner taking it.
Keys held to stay in touch, trailing just 2-1, but she was broken a second time, missing an easy shot to give the Aussie a break point that was converted for a 4-1 advantage.
The American pressured the Barty serve and even have break point, which was saved and she held. A game later, she was a set to the good after another winner.
The second set was much more competitive as Keys smacked a winner to hold for 2-2. Her next service game proved to be decisive as the world number one broke for a 4-2 lead.
Each woman held and Barty stepped up to serve for the match. After losing the first point, her serve, such a potent weapon now, got her to double match point.
Another strong delivery set up a forehand into the open court as the Australian reached the final in Melbourne and looks on course for her third major title.