Both players signed a futures contract in January.
Williams, 27, appeared in two games with the Eagles last season, making three tackles and a pass breakup. He entered the NFL as an undrafted free agent in 2016, signing with the Chargers.
Williams also has played for the Cardinals.
In four NFL seasons, he has appeared in 41 games with 27 starts and has 113 tackles, three interceptions and 23 pass breakups.
The Steelers also officially signed defensive back Shakur Brown, defensive back Mark Gilbert, defensive back Arthur Maulet, receiver Isaiah McKoy, defensive back Lamont Wade and linebacker Jamar Watson. Those signings made Williams and Battle expendable.