Hellcat Challenger versus ZL1 Camaro

I read somewhere that GM claims they have developed a way to "weld" aluminum to steel. Those are my quotes. In the article, they didn't say how, but I'm guessing they are glueing the dissimilar metals together. Anyway, the point they were trying to make is that by "welding" aluminum to steel, and other methods, they are going to cut the weights of their vehicles by up to 500#'s each.