Application of Zr-Based Bulk Glassy Alloys to Golf Clubs

Bulk glassy alloys have high tensile strength, while the Young’s modulus is lower by 20 to 40% than those for the corresponding crystalline alloys. These unique mechanical properties are effective to increase the coefficient of restitution at the impact between a golf club and a golf ball. Bulk glassy alloys have in general been produced by the copper mold casting and die casting methods. We have developed a new manufacturing process for Zr-based bulk glassy alloys. By the use of the new process, we have succeeded in producing a glassy Zr–Al–Ni–Cu alloy in a shell shape with a dimension of about 90×40 mm and a thickness of 3 mm for glassy driver golf clubs. It exhibits excellent mechanical properties such as tensile strength of 1700 MPa, Young’s modulus of 81 GPa, and impact fracture toughness of 130 kJ/m2. These properties are suitable for the material for driver golf club heads. The glassy driver golf club with the shell shape in the impact region was confirmed to have a high coefficient of restitution.