Isotropic Thermal Expansion Properties of Cast Aluminum Plate
Cast aluminum plate delivers isotropic thermal expansion across all orthogonal axes due to its stress-relieved equiaxed grain structure.
Micro-Porosity
Meaning
Internal material voids with dimensions on the micrometer scale typically develop during the solidification or sintering of metals and ceramics. These microscopic cavities, known as micro-porosity, act as stress concentrators that reduce the fatigue life of cast enclosures. In hermetic packages for outdoor electronics, such voids can form leak paths that allow moisture to enter the assembly.
Formation Vector
Gas dissolution and shrinkage during phase change are the primary drivers for the generation of these small voids. As the liquid metal cools, its solubility for hydrogen drops, forcing the gas out of solution to form bubbles. Simultaneously, the contraction of the metal during freezing creates voids if liquid cannot flow into the shrinking regions.
Detection Technique
High-resolution radiography and helium leak testing are utilized to identify these internal defects in critical enclosures. While superficial defects are easy to see, deep internal voids require industrial computerized tomography to map their distribution. This evaluation ensures that only high-density cast parts are sent to assembly.
Structural Impact
Mechanical weakness occurs because the voids reduce the effective load-bearing area and initiate crack propagation under cyclic stress. Designers offset this risk by specifying hot isostatic pressing to collapse the internal voids through the application of high pressure at elevated temperatures. This thermal process restores the mechanical properties of the cast component to values close to those of forged parts.
Implementing these density standards is necessary when the enclosure must protect sensitive transceivers in undersea or high-altitude environments.