A team of researchers in Michigan have come up with a low-cost method to remove 3D printed 1100 aluminum parts from a reusable substrate, and it involves the use of coatings of aluminum oxide and boron nitride. The method has been tested on 1100 aluminum, and A36 low-carbon steel substrates, and the team did “lap shear tests” to assess the interlayer adhesion between the printed metal part and the print substrate. Their method may well have found breakthrough-level success as the parts they creating during their testing didn't warp the substrate and allowed them to easily remove parts from their inexpensive, open-source metal printer. You can read the details of their work here: http://3dprint.com/29944/diy-metal-printing-garage