Tensile Property Improvement in Ti/Al Clad Sheets Fabricated by Twin-Roll Casting and Annealing

Abstract

A new fabrication method of Ti/Al clad sheet by bonding a thin Ti sheet on to Al alloy melt during twin-roll casting was presented to broaden industrial applications of Ti alloys. In the twin-roll-cast Ti/Al clad sheet, a homogeneously solidified microstructure existed in the cast Al side, while a Ti/Al interface did not contain pores, cracks, or lateral delamination, which indicated a successful fabrication. When this cast sheet was annealed at 400 degrees C, metallurgical bonding was expanded by interfacial diffusion, thereby leading to improvement in tensile properties. After the 600 degrees C-annealing, a TiAl3 intermetallic compound was formed at the Ti/Al interface, which deteriorated tensile properties because of its brittle characteristics. The yield and tensile strengths of the 400 degrees C-30-min-annealed sheet (132 MPa and 218 MPa, respectively) were higher than those (103 MPa and 203 MPa, respectively) calculated by a rule of mixtures using tensile properties of a 5052-O Al alloy and a pure Ti. Its ductility was also higher than that of 5052-O Al alloy (25%) or pure Ti (25%) because the strain at the interfacial delamination point reached 41%. The 400 degrees C-30-min-annealed sheet showed the overall homogenous deformation behavior by complimenting drawbacks of mono-layer of Al or Ti.