Effect of thermal-cold cycling treatment on microstructural stability of Al-Cu-Mg alloy hemispherical component

Abstract

The microstructural stability of aluminum alloy hemispherical components in gyroscope navigation systems is the determinant for navigation precision. In this work, a thermal-cold cycling treatment (TCT) was applied to evaluate the microstructural stability of the hemispherical components. The results showed that the dislocations and precipitation of Al2CuMg in the component annihilated with the increasing TCT cycles, improving the microstructural stability. After 16 cycles, the dislocation density reached the minimum value of ∼1.51 × 1014 m−2 in the die fillet area (DFA), indicating an earlier stabilization than that in the bottom of the hemisphere (BOH) after 38 cycles. Such a difference was mainly attributed to the initial dislocation density. The high initial dislocation density in the DFA reduced the nucleation work and diffusion activation energy, which accelerated the nucleation of Al2CuMg phases, thereby reducing the stored energy and lattice distortion remarkably. Additionally, the high initial dislocation density increased the superimposed effect of two dislocations of opposite signs, accelerating the annihilation of dislocations. The annihilation of dislocations and precipitation of tiny Al2CuMg phases contributed to the optimized microstructural stability. In this sense, the TCT may serve as an effective method for the fabrication of aluminum alloy components with high stability for gyroscopes.