Material Properties of High Strength Beryllium Free Copper Alloys
Igor Altenberger , Hans-Achim Kuhn and Hilmar R. Muller
Abstract: High strength copper alloys can be produced either by generating
very fine grained low alloyed single phased or precipitation hardened copper
alloys or by highly alloyed precipitation hardened copper alloys. The latter
process requires special processing methods such as spray forming in order to
achieve a sufficiently homogeneous microstructure. Systematic investigations
on the aging behaviour of the highly alloyed nickel-manganese bronze
CuNi20Mn20 demonstrate that fully crystalline copper alloys with hardness
exceeding 500 HV can be produced. In addition to age hardening, swaging or
severe plastic surface deformation can be used for additional grain refinement
and strain hardening before precipitation hardening. In contrast to
CuMn20Ni20, the low-alloyed precipitation hardened copper alloy
CuNi3Si1Mg exhibits excellent thermal and electrical conductivity while
maintaining acceptable strength after swaging and precipitation hardening.
Finally, a systematic comparison between spray-formed or precipitation high
strength hardened copper alloys and classical well-known materials such as
steels or aluminium alloys was carried out by using material property charts
(Ashby-maps) and highlighting the fields of application and unique property
combinations of copper alloys.
Keywords: high-strength copper alloys; materials selection; spray forming;
precipitation hardening; fatigue; mechanical surface treatment; ultra fine
• Several concepts for designing high-strength copper alloys are suggested: Besides
the classical strengthening mechanisms such as precipitation hardening and cold
working, some more novel methods such as severe plastic deformation followed by
artificial aging, amorphisation as well as in-situ nanocrystallisation of metallic
glasses appear to be promising methods. Preferential hardening of surface zones
(e.g., by mechanical surface treatments) or special processing of semi-finished billets
such as spray forming may further increase the strength and serve to further optimise
the quality and homogeneity of the desired component.
• The strengths of several copper alloys are equally high as those of steels or titanium
alloys while maintaining satisfactory conductivity (Figure 21).
• ‘Ashby-maps’ are very useful tools to explore the potential of copper alloys and
widen their applications, since strength of copper alloys is only attractive in
combination with other functional properties, such as superb electrical and thermal
conductivity, low permeability and good thermal stability (as opposed to aluminium
alloys). Since the commercial success of copper alloys depends so strongly on their
‘secondary properties’ great heed has to be taken by the marketing and development
engineer if copper alloys are to be recommended as the first choice.
• Increasing miniaturisation of electromechanical components will promote the use of
high strength copper alloys in more and more high-end applications.
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