MELBOURNE, Jan. 27 (Xinhua) -- World number three Alexander Zverev leaned on a dominant serve to beat American 25th seed Learner Tien on Tuesday and reach the Australian Open semifinals.
Zverev fired 24 aces and saved all three break points to prevail 6-3, 6-7 (5), 6-1, 7-6 (3) in three hours and 11 minutes, keeping alive his bid for a first Grand Slam title.
"Without my aces, I wouldn't have won today. Obviously very happy with my serve," Zverev said.
With temperatures in Melbourne pushing past 40 degrees Celsius, the roof at Rod Laver Arena was closed, easing conditions for players and fans.
Tien, 20, was playing his first major quarterfinal and initially struggled under the spotlight, but he showed poise to level the match with a forehand winner that lifted the crowd.
Zverev, last year's finalist, regrouped to control the third set and then edged a tight fourth-set tiebreak to seal the win.
The 28-year-old will next face either top seed Carlos Alcaraz or Australian hope Alex de Minaur, who meet later in a night-session quarterfinal.
