Platinum-nickel-based ternary or higher alloys include platinum at about 65-80 wt. %, nickel at about 18-27 wt. %, and about 2-8 wt. % of ternary or higher additions that may include one or more of Ir, Pd, Rh, Ru, Nb, Mo, Re, W, and/or Ta. These alloys are age-hardenable, provide hardness greater than 580 Knoop, ultimate tensile strength in excess of 320 ksi, and elongation to failure of at least 1.5%. The alloys may be used in static and moveable electrical contact and probe applications. The alloys may also be used in medical devices.