Downhole hanger systems and methods for hanging a first structure from a second structure in downhole environments are described. The systems include a first structure and a second structure, with the first structure disposed within the second structure. A composite joint is arranged on an outer surface of the first structure. The composite joint is formed of a material configured to be fused to both the first structure and the second structure and form a hanger joint having a shear strength of at least 2 ksi when the material is fused to the outer surface of the first structure and an inner surface of the second structure.