Austenite Branch Crystals on Residual Stress
Crystal structures are the set of atoms that make up the bulk of a material. Austenite, for instance, is a crystal structure that is a type of iron-carbon alloy, with carbon interspersed between iron atoms in the crystal lattice. Austenite branch crystals (ABCs) are a type of crystal structure that are present in the residual stress of many materials, especially those with low carbon content such as aluminum alloys, stainless steels and titanium alloys.
ABCs are composed of two connected crystal structures, although their shapes and size vary. On a microscopic scale, these crystals form when one crystal structure divides into two smaller crystals. One of the smaller crystals is referred to as the “branch”, while the other is the “parent”. These crystals have a stronger inherent bonding energy between the two structures than between individual atoms, which results in a higher degree of strain energy in the material.
The strain energy stored in the ABCs can be released when they are subjected to the external loads or forces. This energy release can lead to a decrease in the materials strength or have other detrimental effects in certain cases, such as a decrease in the materials ductility or a decrease in the materials toughness. Furthermore, ABCs can affect how the residual stresses in a material are distributed, leading to a decrease in the overall strength of the material.
ABCs also have an influence on the fatigue life of a material. When ABCs are present in a material, they can cause the material to fail sooner than it would without their presence. This is because, due to their inherent bonding energy, ABCs can store extra energy, so when subjected to a cyclic load, this excess energy can be released more quickly than in the absence of ABCs. This can lead to quicker fatigue failure and a higher risk of fracture.
Finally, ABCs can also play a role in the corrosion resistance of certain materials. ABCs with higher cross-sectional areas can cause local concentration of corrosive species, and the presence of ABCs can also increase the galvanic current between certain metals. This increased current can lead to increased corrosion in the material.
ABCs are a common phenomenon in many materials, and they can have serious consequences on the performance and mechanical properties of the material. Therefore, it is important to understand the composition, morphology, and properties of ABCs, especially in materials prone to residual stress. Only by understanding these features of ABCs can engineers determine whether or not the presence of these crystals will have an adverse impact on the overall performance of the material, and adjust their design accordingly.
