(1. 沈陽(yáng)航空航天大學(xué) 航空制造工藝數(shù)字化國(guó)防重點(diǎn)學(xué)科實(shí)驗(yàn)室，沈陽(yáng) 110136；
2. 沈陽(yáng)飛機(jī)設(shè)計(jì)研究所，沈陽(yáng) 110035)
摘 要: 采用冷金屬過(guò)渡(CMT)電弧增材制造技術(shù)制備了TC4鈦合金樣品，測(cè)試了沉積態(tài)試樣的拉伸性能、沖擊性能和疲勞性能，討論電弧增材制造鈦合金成形件的疲勞斷裂機(jī)理。結(jié)果表明：經(jīng)歷CMT工藝條件下的快速熔凝過(guò)程后，鈦合金成形件內(nèi)宏觀組織由外延生長(zhǎng)的粗大β柱狀晶組成，顯微組織為細(xì)長(zhǎng)α片層和網(wǎng)籃組織。成形件拉伸強(qiáng)度較高，達(dá)到鍛件拉伸強(qiáng)度水平，但是塑性較低，略低于鍛件塑性，且存在一定的各向異性，拉伸斷口呈現(xiàn)半解理斷裂與半韌性斷裂特征。沉積態(tài)鈦合金成形件具有良好的沖擊性能，但沖擊性能的各向異性并不顯著。鈦合金成形件的高周疲勞極限為460 MPa，疲勞源均形核于條狀未熔合缺陷及氣孔缺陷處。缺陷直徑越大，距離表面越近，應(yīng)力集中現(xiàn)象就越明顯，導(dǎo)致樣品具有較低的疲勞強(qiáng)度和疲勞壽命。
關(guān)鍵字: CMT電弧增材制造；TC4鈦合金；顯微組織；拉伸性能；疲勞性能
（1. Key Laboratory of Fundamental Science for National Defense Aeronautical Digital Manufacturing Process, Shenyang Aerospace University, Shenyang 110136, China;
2. Shenyang Aircraft Design Institute, Shenyang 110035, China）
Abstract:TC4 titanium alloy samples were fabricated by cold metal transfer wire arc additive manufacturing process(CMT-WAAM).Tensile strength, impact toughness and fatigue resistance of the samples in as-deposited condition were evaluated. The fatigue fracture mechanism of the WAAM-fabricated samples was investigated. The results show that the macrostructure of the as-deposited samples is consists of coarse β columnar crystals grown epitaxially. And the microstructure is composed of α elongated lamellar and basket weave due to low heat input of CMT. The tensile strength is high, reaching the level of forgings, but the plasticity is low, slightly lower than that of forgings, and there is a certain anisotropy. The tensile fracture shows semi-cleavage and semi-ductile fracture. The WAAM-fabricated samples, showing obvious anisotropy, have higher tensile strength and lower plasticity compared with the forgings. The tensile fracture shows a semi-cleavage and semi-ductile fracture mechanism. The as-deposited samples show a good impact ductility, and the anisotropy of impact performance is not significant. The fatigue limit of the as-deposited sample is 460 MPa, and the fatigue crack sources nucleate at strip-shaped incomplete fusion and pore defects. With the increase of the size of defect diameter and decrease of distance between sample surface and defect, stress concentration becomes more critical, which results in a lower fatigue strength and a shorter fatigue life.
Key words: CMT wire arc additive manufacturing; TC4 titanium alloy; microstructure; tensile strength; fatigue property
