Ti150高温钛合金具有优异的高温蠕变性能，在先进航空发动机的关键部件中得到广泛应用。激光增材制造（LAM）技术作为一种新型成形方式，在复杂精密构件的成形及组合制造上具有很大的优势。Ti150合金通常采用铸造、锻造等传统方式成形，而采用LAM技术成形的研究尚未见报道。本文采用激光金属沉积（LMD）和激光选区熔化（SLM）两种LAM技术成形Ti150合金样品，研究了沉积层及基板热影响区的组织特征和性能特点，分析了不同热处理工艺制度对沉积态组织和性能的影响规律。取得以下主要研究结果：（1）研究了LAM-Ti150合金沉积层及基板热影响区的组织演化规律。LAM-Ti150合金沉积层的微观组织均由α′马氏体片层组成，但SLM-Ti150合金沉积层α?马氏体片层的尺寸与LMD-Ti150合金相比较为粗大。SLM-Ti150合金的基板未受到上方激光能量较大的热影响，上部组织形貌未发生明显改变，而LMD-Ti150合金的基板受到上方激光能量较大的影响，上部形成了明显的由非均匀组织组成的热影响区。（2）进一步研究了LAM-Ti150合金沉积层α′马氏体的亚结构特征。物相鉴定结果表明，LAM-Ti150合金的显微组织与传统成形方法存在较大差异。LAM-Ti150合金沉积层α′马氏体的内部存在着高密度位错，同时有纳米级沉淀相硅化物(Ti,Zr)5Si3沿晶界析出，导致其力学性能呈现出高强度、低塑性的特点。因此为满足工业应用标准，需要通过后续热处理工艺提高其塑性。（3）研究了不同固溶温度下，LAM-Ti150合金固溶+时效组织的演变规律。当固溶温度为925 ℃时，α′马氏体转变为α相片层，并且发生粗化；当固溶温度为975 ℃时，片层α相球化为短棒状；当固溶温度为1030 ℃时，α相进一步发生球化，转变为球状颗粒。球化机制发生的基础是LAM-Ti150合金的马氏体结构及其内部的高密度位错。位错重排形成的亚晶界以及相转变过程形成的新晶界，导致边界分裂，进而发生球化。（4）制定了LAM-Ti150合金强塑性匹配良好的热处理制度。经过1030℃/2h/AC+700℃/2h/AC的热处理后，LAM-Ti150合金得到了强塑性匹配良好的双态组织。SLM-Ti150合金沉积态试样的室温抗拉强度和延伸率分别为1151 MPa和4.8%，热处理试样的室温抗拉强度和延伸率分别为1178 MPa和9.0 %，强度和塑性得到了提高。
Ti150 high temperature titanium alloy has excellent high-temperature creep properties and is widely used in key components of advanced aeroengine high-pressure compressor. As a revolutionary manufacturing method, laser additive manufacturing (LAM) technology has great advantages in the forming and combined manufacturing of complex precision components. Ti150 alloy is usually formed by traditional methods such as casting and forging, while the research on forming by LAM technology has not been reported. In this thesis, Ti150 alloy samples are fabricated by laser metal deposition (LMD) and selective laser melting (SLM), the microstructure and mechanical properties of deposited layer and substrate heat affected zone are studied, and the effects of different heat treatment processes on the microstructure and properties of the deposited layer are analyzed. The main research results are as follows:(1) The microstructure characteristics of deposited layer and substrate heat affected zone of LAM-Ti150 alloy is studied. The microstructure of LAM-Ti150 alloy deposited layer is α′ martensite lamellar, but SLM-Ti150 alloy deposited layer’s α′ martensite lamellar is coarser than that of LMD-Ti150 alloy. The substrate of SLM-Ti150 alloy is not greatly affected by heat source, so the microstructure has not changed significantly. While the substrate of LMD-Ti150 alloy is affected by the heat source, and an obvious heat affected zone composed of non-uniform structure is formed in the upper part of the substrate. (2) The α′ martensite substructure characteristics of LAM-Ti150 alloy deposited layer is further studied. The phase identification results show that the microstructure of LAM-Ti150 alloy deposited layer is quite different from the traditional forming method. There are high-density dislocations in α′ martensite structure, and the nano precipitate silicide (Ti,Zr)5Si3 precipitates along the grain boundary, which resulting in its mechanical properties showing the characteristics of high strength and low plasticity. Therefore, in order to meet the industrial application standards, it is necessary to improve its plasticity through subsequent heat treatment process.(3) The evolution mechanism of solution aging microstructure of LAM-Ti150 alloy at different solution temperatures is studied. When the solid solution temperature is 925℃, the metastable phase α′ martensite transforms into stable α phase lamellar, and the α phase lamellar is coarsened. When the solid solution temperature is 975℃, the α phase lamellar is is spheroidized into short rod shape. When the solid solution temperature is 1030℃, the α phase lamellar is further spheroidized and transformed into spherical particles. The basis of spheroidization mechanism is the α′martensitic structure and its high-density dislocations of LAM-Ti150 alloy. The sub grain boundary formed by dislocation rearrangement and the new grain boundary formed by phase transformation lead to boundary splitting, and then spheroidize.(4) The heat treatment system with good strength and plasticity matching of LAM-Ti150 alloy is established. After the heat treatment of 1030℃/2h/AC+700℃/2h/AC, the LAM-Ti150 alloy obtains a bimodal structure with good strength and plasticity matching. The tensile strength and elongation at room temperature of Ti150 alloy fabricated by SLM are respectively 1151 MPa and 4.8%. After the heat treatment, the tensile strength and elongation at room temperature of Ti150 alloy fabricated by SLM are respectively 1178 MPa and 9.0%, the tensile strength and elongation are improved.
