Serena Williams has continued her pursuit of a record seventh Australian Open singles title with a straight-sets quarterfinal win over Johanna Konta.

Williams had too much firepower for the British ninth seed, winning 6-2 6-3 in 75 minutes at Melbourne Park on Wednesday.

Williams' progress to the semifinals means players aged 36 (her sister, Venus Williams), 35 and 34 (her opponent Mirjana Lucic-Baroni) will play off for two places in the final.

"No matter what happens, somebody 34 or older will be in the final," the 22-time major winner said. "That's great."

Serena Williams and Lucic-Baroni will play the second of the semifinals on Thursday, following Venus Williams against her fellow American Coco Vandeweghe, who is 25.

Earlier an emotional Lucic-Baroni continued her remarkable run into the semifinals with a topsy-turvy 6-4 3-6 6-4 upset victory over No.5 seed Karolina Pliskova.

It came 18 years after Lucic-Baroni's only previous grand slam semifinal appearance.

The Croatian then spent many years away from the sport and later claimed she had been abused from early childhood by her father.

"I can't believe it - this is crazy," said Lucic-Baroni.

"God is good - that's really all I can say."

The world No.79 said one day she would open up fully about all the hardships she has endured before this unexpected late-career renaissance.

"I know this means a lot to any player to reach the semis, but for me it is overwhelming," she said.

The 34-year-old took a medical timeout when trailing 3-4 in the final set against Pliskova on Wednesday, before returning to streak through the final three games in a match lasting one hour and 48 minutes.

Both players had plenty of trouble serving throughout, with the Czech dropping serve three times in the decider.(Stuff)