(西北工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院 凝固技術(shù)國(guó)家重點(diǎn)實(shí)驗(yàn)室，西安 710072)
摘 要: 采用光學(xué)顯微鏡和掃描電鏡觀察分析了Ti60合金熱暴露前后拉伸試樣的顯微組織、斷裂方式及其斷口形貌。結(jié)果表明：Ti60合金塑性對(duì)試樣表面富氧層較為敏感，帶有富氧層的試樣塑性較低；熱暴露前后試樣斷裂方式發(fā)生變化，未經(jīng)熱暴露的試樣，斷裂起源于試樣中心部位，斷面凹凸不平，為典型的韌窩型斷裂；毛坯熱暴露斷口上呈現(xiàn)出大量的解理小平面，也可以觀察到韌窩形貌，為混合型斷口；試樣熱暴露后，裂紋起源于試樣表面，在微觀斷口上除了斷裂小平面外，還有大量的撕裂棱，表現(xiàn)為斷裂沿著α片層界面擴(kuò)展的特征；在高溫長(zhǎng)時(shí)間暴露過(guò)程中，氧除了污染試樣表面，還會(huì)溶解在基體中形成脆性富氧層，這是影響Ti60合金熱穩(wěn)定性能的重要原因。
關(guān)鍵字: 高溫鈦合金；熱穩(wěn)定性能；富氧層；斷口形貌
fracture behaviors of Ti60 alloy
（State Key Laboratory of Solidification Processing, School of Materials Science and Engineering,
Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:The tensile properties of Ti60 titanium alloy after high temperature exposure were investigated. The variation and morphologies of fracture for Ti60 titanium alloy after exposure were analyzed. The results show that the tensile properties of the unexposured specimens at room and high temperature can meet the specification. After thermal exposure, the strength of the specimens increases but the ductility decreases. The dominant damage mechanism changes after thermal exposure. Before exposure, the crack initiates near the center of the specimens, and the fractographs exhibits honeycomb morphology. After thermal exposure, a brittle oxygen-riched subsurface layer forms, the crack initiates on the surface of the tensile specimens, the fracture is hybrid fracture of dimple and quasi-cleavage, and the fracture facet shows the characteristic of lamellar along α platelet colony. During long-term high temperature exposure, the oxygen absorbed in alloy, except for forming oxidation layer, dissolves into the matrix and forms the surface oxygen-enriched layer which becomes an important factor of decreasing the thermal stability of Ti60 alloy.
Key words: high temperature titanium alloy; thermal stability; oxygen-enriched layer; fracture morphology
