PH copper alloys are heat-treatable alloys. The high strength of PH copper alloys is attributed to the uniform distribution of fine precipitates of second — phase particles in the copper matrix. PH copper alloys are produced by conventional solution treatment

and aging treatment. Solution treatment produces a homogeneous solid solution by the heating of an alloy to a sufficiently high temperature to dissolve all solutes. The alloy is then quenched to a lower temperature to create a supersaturated condition. A subsequent aging treatment heats the alloy to an intermediate temperature below the solvus tem­perature, to precipitate fine second-phase particles. Precipitates not only give rise to high strength, but also reduce the solute content in the matrix, main­taining good conductivity. The strength of a PH alloy depends on particle size, particle shape, volume frac­tion, particle distribution, and the nature of the inter­phase boundary.7 Despite their ability to develop significant strength, PH copper alloys may be soft­ened substantially as a result of precipitation coars­ening (overaging) at intermediate to high service temperatures or because of recrystallization during brazing or diffusion bonding. Therefore, heat treat­ment and thermal processing histories can have a large influence on the strength and conductivity of this class of alloys.

A number of commercial PH copper alloys have been investigated for applications in fusion design, for example, CuCrZr, CuNiBe, and CuNiSi.