材料为QAl9-4铝青铜的船用推进器转向油缸接头，在下水投入使用8个月后出现早期断裂失效。从断口形貌、化学成分、力学性能、显微组织等方面，对QAl9-4铝青铜油缸接头进行断裂原因分析。结果表明：QAl9-4铝青铜原材料力学性能偏低，铅、铁元素含量超标，增加了合金的脆性并降低了合金的耐腐蚀性；基体组织严重偏析，在交变载荷及环境腐蚀的作用下在表面腐蚀锈斑处萌生裂纹源，发生应力腐蚀开裂并最终导致脆性断裂。

The early fracture failure happened to the steering cylinder joint of the marine propeller made from QAl9-4 aluminum bronze after using in the water for eight months. Based on the fracture morphology, chemical composition, mechanical properties, microstructure and so on, the fracture reasons for the cylinder joint of QAl9-4 aluminum bronze were analyzed. The results show that: mechanical properties of the raw material were low, the brittleness of the alloy increased and the corrosion resistance of the alloy reduced because of the overproof Pb and Fe elements; the matrix structure segregated severely, and the crack source generated in the position of surface corrosion pitting under the action of alternating load and environmental corrosion; the stress corrosion cracking happened and finally led to the brittle fracture.