Robert Downey Jr. signs on as Iron Man for next two Avengers LOS ANGELES (Reuters) - Actor Robert Downey Jr., who has gained huge box-office success with his portrayal of Iron Man, has signed on to star as the superhero in the next two installments of the "The Avengers," Marvel Studios said on Thursday. Downey, 48, was one of the main stars of the 2012 all-star superhero film "The Avengers," which united Iron Man, The Hulk, Captain America, Thor and the Black Widow. "The Avengers," made by Walt Disney Co's Marvel Studios, became the third highest-grossing film of all time, with $1.5 billion at the worldwide box office. Downey is expected to be joined by Chris Evans, Chris Hemsworth, Mark Ruffalo and Scarlett Johansson in reprising their superhero roles for "The Avengers 2." "The Avengers 2," set for release on May 1, 2015, will be directed by Joss Whedon. Marvel said the film would reunite the superheroes from the first film, as well as introducing Marvel characters never seen in film before. The three "Iron Man" films starring Downey from 2008 to 2013, have grossed more than $2.4 billion at the worldwide box office. "Iron Man 3" released last month has become the highest-grossing film of the year, with $1.2 billion in global ticket sales, and the fifth highest-grossing film of all time, Marvel said in a statement. Reporting by Piya Sinha-Roy; Editing by Peter Cooney