Medium & High Voltage Electrical Contacts

Dispersion Strengthened Copper

Dispersion Strengthened Copper

Modison Limited has developed high performance dispersion strengthened copper in order to provide high mechanical strength along with Copper’s high electrical conductivity.

Copper has been widely used in many industrial applications such as: contact supports, frictional break parts, electrode materials among others. Pure copper though having excellent electrical and thermal properties, has relatively low mechanical properties, like low hardness, low tensile and creep strength. Hence there is an increased demand for copper alloy having high electric conductivity and mechanical strength.

The development of Cu-based alloys having high tensile strength and hardness along with the electrical and thermal properties have picked up pace in the recent years. Such alloys find their applications in a coil material for generating high magnetic fields, spot welding electrodes, high performance switches etc. In a recent development such Cu alloys are also proposed to be used in the thermonuclear reactors. Due to their incompatibility, it is difficult to obtain a copper alloy having both a high electrical conductivity and a high mechanical strength. Many conventional ingot metallurgy manufacturing methods of alloying, solution hardening and precipitation hardening have been attempted, but these have not yielded the required fruits. Moreover alloying results in the considerable loss in the electrical conductivity. Hence a need to identify a technique where one can increase copper strength without disturbing its electrical and thermal conductivities. In this respect Metal matrix composites are considered as important engineering materials with potential applications in a variety of fields.

Some metals may be strengthened by incorporating in them relatively small quantities of another material such that the added materials do not form a homogeneous solid solution phase, but are uniformly dispersed in fine particulate form throughout the metal. These small quantity material forms the dispersoid and the metal the parent matrix. Many ceramic oxides are utilized as the dispersoid due to their insolubility in the metal matrix, stability at high temperature and better mechanical properties. Such metal matrix composites combine both metallic properties and ceramic properties. Strengthening copper by means of a dispersed phase, in contrast with the conventional methods of solid solution hardening or precipitation hardening, renders a significant increase in strength while retaining a substantially pure metal matrix with very little or virtually no alloying element remaining in solid solution.

This has the advantage of giving markedly higher strength without significant loss in electrical or thermal conductivity or in corrosion resistance.

Micrograph of Alumina strengthened Copper Alumina is well dispersed in copper

Oxide dispersion strengthened copper has been identified as an effective method to increase copper strength without affecting its electrical and thermal properties. The advantages of such an alloy are:

  • Resistance to softening at elevated temperatures and the electrical and thermal properties are retained,
  • Reinforced matrix composites possess an increased wear resistance and better refractory properties than the non-reinforced ones. The dispersions are generally stable refractory metal oxides and amongst these metal oxides, alumina as dispersion has found more applicability because of its obvious mechanical properties (high toughness and hardness with low bulk density).
  • Cost Competitive

Due to the presence of alumina, copper alloy with alumina cannot be produced by the conventional melting and casting process. Hence alumina reinforced copper alloy is manufactured by the powder metallurgy. The alumina is found to be uniformly dispersed in the copper matrix eventually giving better mechanical properties to the composite while retaining the physical properties.

In Modison the powder metallurgy technique is utilized to manufacture alumina strengthened copper. Fine individual powders of pure copper and alumina are blended in a mixer and then compacted, sintered and machined. The Modison alumina strengthened copper has competitive mechanical and physical properties with uniformly dispersed alumina in the copper matrix.