Golf ball including metal foam layer

A golf ball comprising:

• at least one first layer comprised of at least one metal foam having a first specific gravity of no greater than 0.25, and
• at least one second layer that is disposed radially outward from the at least one first layer comprised of the at least one metal foam,
• wherein the at least one metal foam of the at least one first layer has a first tensile strength, and the at least one second layer is formed from a material having a second tensile strength, wherein the golf ball has a strength gradient ratio defined by a ratio of the first tensile strength to the second tensile strength, and the strength gradient ratio is at least 2.0.

A golf ball comprising:

• a core layer comprised of at least one metal foam having a first specific gravity of no greater than 0.25, wherein the at least one metal foam is formed from at least one of aluminum, copper, tantalum, tin, titanium, or zinc, wherein the core lacks any rubber, and wherein the at least one metal foam has a porosity of at least 70.0%, and
• at least one second layer that is disposed radially outward from the core layer, wherein the at least one second layer has a second specific gravity, and a density layer gradient ratio is defined by a ratio of the first specific gravity to the second specific gravity, and the density layer gradient ratio is no greater than 0.30.