forehand down the line winner to hold her service game to go ahead 2-0.
Williams held serve in her second service game of the match as did Ivanovic as she led 3-1.
With Williams serving, Ivanovic failed to convert any of three breakpoints for a 4-1 lead as at the same time Williams raised the level of her game to reach deuce each time.
Williams erased the first and second breakpoints with an ace down the tee and a crosscourt forehand winner.
Serving to stay in the set at down 4-5, Ivanovic fell behind 0-30 before hitting a crosscourt backhand winner to reach 15-30.
However two consecutive double faults from Ivanovic ended the set she would drop serve.
In set two, Williams broke serve at 2-1 and again at 4-1 to take a 5-1 lead.
Serving for the match and up 15-0, the American struck an ace down the tee then another ace out wide to reach match point at 40-0.
Ivanovic hit a forehand down the line wide to end the match after 1 hour and 2 minutes of play.
Williams finished the day with 12 aces among her 26 winners.