QAl9-4鋁青銅轉向油缸接頭斷裂失效分析

QAl9-4鋁青銅轉向油缸接頭斷裂失效分析Fracture Failure Analysis of QAl9-4 Aluminum Bronze Steering Cylinder Joint

材料為QAl9-4鋁青銅的船用推進器轉向油缸接頭，在下水投入使用8個月后出現早期斷裂失效。從斷口形貌、化學成分、力學性能、顯微組織等方面，對QAl9-4鋁青銅油缸接頭進行斷裂原因分析。結果表明：QAl9-4鋁青銅原材料力學性能偏低，鉛、鐵元素含量超標，增加了合金的脆性并降低了合金的耐腐蝕性；基體組織嚴重偏析，在交變載荷及環境腐蝕的作用下在表面腐蝕銹斑處萌生裂紋源，發生應力腐蝕開裂并最終導致脆性斷裂。

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.

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