Failure Analysis on Fracture of ZL114A Core Box in Vibrant Testing

Vibrant range increasing phenomenon was found after the core box working for 60 h, and after disassembling it was found that cracking happened at position of the supporting seat reinforcing rib. The cracking feature and cause of the core box were analyzed by means of macro observation, fracture analysis, metallographic examination, hardness testing, chemical compositions analysis and mechanical properties test. The results show that the crack mode was fatigue cracking. The cracking was caused by the cast aluminium freedom interface defect on surface, which increased the stress concentration of the area. It was suggested to strictly control the casting process or to have a certain machining margin in thickness direction to improve the surface integrality of the core box.