Unalloyed rhymes with:
alkaloid, amyloid, celluloid, mongoloid, nedlloyd, ackroyd, adenoid, alkaloid, amyloid, android, asteroid, aykroyd, boothroyd, celluloid, corticosteroid, hemorrhoid, holroyd, mongoloid, nedlloyd, oldroyd, ovoid, paranoid, polaroid, rheumatoid, rhizoid, sinusoid, spheroid, vescinoid
Unalloyed sounds like:
unhealthy, unleaded, unload, unloaded, unwieldy