Abstract: The limited clevis rod of a tractor fractured during no-load lifting test. The failure reasons of the limited clevis rod were analyzed by means of macroscopic inspection, scanning electron microscope observation, metallographic examination, hardness testing, tensile test and so on. The results show that:the aluminum content of the raw material of the limited clevis rod was relatively high; during the cooling process after casting solidification, flake aluminum nitride inclusions, which formed by the aluminum and nitrogen element, precipitated in the prior austenite grain boundaries, caused the dramatical decrease of material plasticity and toughness, and resulted in the brittle fracture of the parts under extremely large force.