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For the typical alloy CuBe1.9 (1.8- 2%) the alloy is heated between 720°C and 860°C. At this point the contained beryllium is essentially “dissolved” in the copper matrix (alpha phase). By rapidly quenching to room temperature this solid solution structure is retained. The material at this stage is very soft and ductile and can be readily cold worked by drawing, forming rolling, or cold heading. The solution annealing operation is part of the process at the mill and is not typically used by the customer. Temperature, time at temperature, quench rate, grain size, and hardness are all very critical parameters and are tightly controlled by NGK Berylco.
Age hardening significantly enhances the material’s strength. This reaction is generally carried out at temperatures between 260°C and 540°C depending on alloy and desired characteristics. This cycle causes the dissolved beryllium to precipitate as a beryllium rich (gamma) phase in the matrix and at the grain boundaries. It is the formation of this precipitate which causes the large increase in material strength. The level of mechanical properties attained is determined by the temperature and time at temperature. It should be recognized that beryllium copper has no room temperature aging characteristics. Material is available from NGK Berylco in the annealed cold worked or age hardened condition.
Age Hardenable Tempers - This term means the material can be strengthened by simple heat treatment after stamping or forming. The strength level will be roughly doubled by optimum heat treatment.
Heat Treated Tempers - These tempers describe the resulting strength after optimum heat treatment of their age hardenable counter parts.
Mill-Hardened Tempers - These tempers have been heat treated through carefully controlled processing to develop a strength level between age hardenable and fully heat treated tempers. They are normally formed and put into service at this strength. They are also used to provide sturdy, miniature parts for subsequent full heat treatment. This approach protects small parts from damage and improves dimensional stability during final heat treatment.
Heat treatment is the most important process for this alloy system. While all copper alloys are hardenable by cold working, beryllium copper is unique in being hardenable by a simple low temperature thermal treatment. It involves two basic steps. The first is called solution annealing and the second, precipitation or age hardening.
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