Is it possible to become a researcher in Artificial intelligence through a statistics phd?
Nobody cares what species of PhD you have.
If you publish research in machine learning venues, you are a machine learning researcher.
In particular, if you publish good research in good machine learning venues, you are a good machine learning researcher.

Just at my own university, I can think of machine learning researchers with PhDs in computer science, statistics, applied mathematics, pure mathematics, computer engineering, electrical engineering, mechanical engineering, astronomy, linguistics, library science, operations research, aeronautics, and economics.  I'm sure I've missed a few.  They all do different types of machine learning, but whatever.

The correct question to ask is Will a statistics PhD from [department] working with [advisor] support my ambition to work in machine learning?  And the answer to that question depends on [department] and [advisor].