A method of making a diffusion bonded sputter target assembly is provided. A target blank comprising a first metal or alloy has a first surface defining a sputtering surface and a second surface. A second metal or alloy is placed around the target blank. A backing plate is provided adjacent the second metal or alloy that is positioned alongside of the second target surface. This assembly is then diffusion bonded, and a portion of the second metal overlying the sputtering surface of the target is removed to expose the target sputtering surface. W target or W alloy target/Ti or Ti alloy backing plate assemblies are provided with an Al interlayer positioned intermediate the W or W alloy target and backing plate. The assembly has a bond strength exceeding 50 MPa.