A wire structure, which may be configured for a semiconductor device, is disclosed. The wire may include an elongate flexible core formed of a conductor material and a cladding layer covering an outer surface of the core. The cladding layer may be a conductor. In various aspects the cladding layer and core have different grain sizes. An average grain size of the core material may be several orders of magnitude greater than an average grain size of the cladding layer material. The cladding layer may be an alloy having a varying concentration of a minor component across its thickness. Methods of forming a wire structure are also disclosed.