4J29 Expansion Alloy 4J29 Iron-Nickel-Cobalt Composition

Introduction to Precision Alloy 4J29

With the increasing demands for high-resolution detection accuracy in space-based Earth observation and deep space exploration, operating photoelectric systems in low-temperature environments has become an effective approach, imposing higher requirements on system integration. In the optimization design of cryogenic integrated systems, computer simulations require accurate data on material thermal properties and mechanical performance. However, with the development and application of new materials, data for these novel materials in the cryogenic range are often lacking. 4J29 Kovar alloy (also known as Kovar alloy) possesses unique expansion characteristics, with coefficients of thermal expansion and rates of thermal contraction closely matching those of borosilicate hard glass during heating and cooling processes. This enables strong matched sealing with glass, making it suitable for vacuum sealing. It is currently a commonly used material in aerospace infrared cryogenic photoelectric systems. Additionally, 4J29 Kovar alloy exhibits good low-temperature microstructural stability above the liquid nitrogen temperature range, along with excellent processing, welding, and electroplating properties, making it a common material for electrical connectors in aerospace cryogenic systems.

Scott developed 4J29 Kovar alloy in the 1930s. The expansion coefficient of 4J29 Kovar alloy is relatively close to that of borosilicate hard glass, which can effectively wet the oxide film on the surface of 4J29 alloy, ensuring the sealing of encapsulated devices. The emergence of this alloy quickly replaced refractory metals such as tungsten and molybdenum and was widely used as a sealing structural material for vacuum instruments in aircraft and spacecraft. With the extensive use of hard glass as a packaging material for semiconductor transistors, 4J29 alloy has been widely applied in the manufacturing of transistors, integrated circuits, and other devices.

Chemical Composition of 4J29

4J29 (Executive Standards GB/T 15018-1994 YB/T 5231-1993)

Thermal Properties of Precision Alloy 4J29

4J29 Kovar alloy exhibits different thermal properties in the cryogenic and room temperature ranges, and these changes have a certain impact on system design, which has attracted the attention of researchers. This study used the "steady-state longitudinal heat flow method" to measure the thermal conductivity of 4J29 Kovar alloy in the 77–300 K temperature range, the "steady-state method" to measure its specific heat capacity in the 77–300 K temperature range, and an elastic modulus testing machine to measure its elastic modulus coefficient in the 77–300 K temperature range. The obtained thermal property parameters and mechanical performance parameters for 4J29 Kovar alloy from liquid nitrogen to room temperature meet engineering requirements. Thermal property tests show that the specific heat capacity and thermal conductivity of 4J29 Kovar alloy decrease with decreasing temperature, with measurements in the 77 K range being more than three times smaller than those at room temperature. In mechanical elastic modulus tests, the elastic modulus value changes little with decreasing temperature, with the trend showing randomness. By using TC4 titanium alloy as a standard reference material for comparison and error analysis, it is confirmed that the measurement errors are within an acceptable range, making the data suitable for reference by engineering system designers.

Various specifications of plates, rods, strips, wires, discs, ring blanks, and ring forgings are available. Rods are supplied in forged-rolled condition, with surfaces ground or turned; discs and ring blanks are supplied in forged condition; rings are supplied in solution-treated condition; plates are supplied after solution treatment, alkali-acid pickling, straightening, and edge trimming; strips are delivered after cold rolling, solution treatment, and descaling; wires are delivered in solution-pickled coil or straight bar form, or in solution-treated straight bar fine-ground condition.