Changes in metal microstructure caused by die casting
During the Precision Shaft Die Casting Processing process, the molten metal is filled and solidified under high pressure and high speed, which will cause significant changes in the microstructure of the metal. First, the rapid cooling rate of die casting leads to grain refinement, forming a fine and uniform equiaxed grain structure. At the same time, due to the action of high pressure, the dislocation density inside the metal increases and the structure becomes denser. These changes in microstructure affect the mechanical properties of shaft parts to a certain extent, and then have an important impact on their fatigue performance.
Grain refinement improves fatigue performance
Grain refinement is an important microstructural change brought about by die-casting processing, which has a positive impact on fatigue performance. Fine grains can increase the grain boundary area and hinder dislocation movement, thus improving the strength and hardness of the material. Under the action of fatigue load, grain boundaries can effectively prevent the expansion of cracks, causing cracks to deflect or stagnate at the grain boundaries, increasing the resistance to crack expansion and significantly improving the fatigue life of shaft parts. For example, in some precision shaft parts used in the aerospace field, the fine-grained structure obtained through die casting enables them to withstand higher cyclic loads, ensuring the reliability of the equipment under complex working conditions.
Effect of increased dislocation density
The high dislocation density generated during the die-casting process also plays an important role in fatigue performance. The existence of dislocations causes stress concentration inside the metal. Under fatigue loads, these stress concentration points can easily become the initiation points of cracks. However, an appropriate increase in dislocation density can produce a work hardening effect through dislocation interaction and improve the yield strength and fatigue resistance of the material. At the same time, the movement and interaction of dislocations can also consume energy, further hindering the expansion of cracks, allowing shaft parts to maintain good stability under cyclic loads and reduce the risk of fatigue failure.
Relationship between tissue density and fatigue properties
The die-casting process makes the metal structure denser, reducing the number of internal pores and defects. This dense structure can effectively improve the load-bearing capacity of shaft parts, making it less likely to cause local stress concentration when bearing fatigue loads. During the fatigue process, the denseness of the structure can prevent cracks from rapidly expanding at defects such as internal pores, thereby extending the fatigue life of the part. On the contrary, if the structure is not dense enough and there are many pores and defects, these parts will become the preferential expansion paths of fatigue cracks, greatly reducing the fatigue performance of shaft parts. Therefore, the dense structure obtained by Precision Shaft Die Casting Processing is crucial to improving its fatigue performance.
