Alize Cornet survived stifling heat to outlast former world No 1 Simona Halep 6-4, 3-6, 6-4 in a battle of attrition at the Australian Open on Monday, advancing to her first Grand Slam quarter-final where she will meet Danielle Collins.

Collins earlier became the third American woman after Madison Keys and Jessica Pegula to reach the quarters of this year's event after she overhauled Elise Mertens 4-6 6-4 6-4.

Frenchwoman Cornet, making her 63rd main draw appearance at a Grand Slam, improved her record against 2018 finalist Halep to 4-1 after the 32-year-old came through a battle lasting two hours and 33 minutes at the Rod Laver Arena.

Cornet, who had both thighs heavily taped, buried her face in a towel and broke into tears after converting her third match point.

'It was a battle with Simona today in this heat. After 30 minutes of the game we were both dying on the court. We kept going for two and a half hours with all our heart,' Cornet said on court amid warm applause from the crowd.

'Congrats to Simona because I know she struggled a lot and I admire this player so much. She's such a fighter and an example to me. To beat her today to go to my first quarter-final is a dream come true.

'I don't know what to say. It's just magic. It's never too late to try again.'

Halep missed Wimbledon and the French Open during an injury-plagued 2021 but looked in peak form at the start of the season as she notched nine wins in a row, including a title in Melbourne in the lead-up to the Australian Open.

The Romanian had conceded only 12 games en route to the fourth round but the 30-year-old looked exhausted as the match progressed, leaning on her racquet between points to catch her breath.

Conditions were no less brutal earlier on Monday as Collins needed all her resilience to come through a gruelling clash of former semi-finalists, the 27th-seeded American taking the win with a barrage of power hitting as Mertens served to stay in the match.

Belgian Mertens saved two match points, the second with a gutsy second serve, but then surrendered meekly on the third with a double-fault.

'I think I had my ups and downs during the match, mentally and physically,' said Collins, who looked to be hampered by a back issue during the contest.

'Elise was really working me to the max. Some of the points were incredible, how many balls she was getting back. So I had to kind of put some pressure on her.'