激光沉积TA15热处理工艺研究

发布时间：2018-03-06 08:28

本文选题：激光沉积制造/修复　切入点：TA15钛合金　出处：《沈阳航空航天大学》2017年硕士论文　论文类型：学位论文

【摘要】：激光沉积制造技术利用“离散+堆积”的增材成形思想,采用同轴送粉和激光熔覆数字化成形进一步控制工件的成形精度,然而在成形过程中由于激光的高密度能量累积以及散热方向的单一性,导致成形件组织分布不均匀,力学性能出现各向异性。热处理工艺具有调节显微组织和改善力学性能等作用,因此将热处理工艺应用于激光沉积制造成形件。由于激光沉积制造技术的特殊性,导致其与传统锻造或铸造等方法的组织明显不同,致使热处理工艺需要重新摸索和制定。激光沉积制造技术包含激光沉积制造和激光沉积修复两种方式,两种方式需要截然不同的热处理工艺。对于激光沉积制造TA15钛合金,因为α+β相区温度较大,首先在α+β相区进行多组不同温度梯度的退火处理实验,研究在α+β相区不同退火温度对显微组织以及室温拉伸力学性能的影响,并在显微组织较均匀以及力学性能较好的温度区间内进一步细化热处理温度;其次在α+β相区和β相区进行双重退火实验,研究双重退火对显微组织以及力学性能各向异性的影响。对于激光沉积修复TA15钛合金,在热处理时要保证基体组织的稳定性,因此主要考察不同修复方式下热处理对显微组织组织和力学性能的影响;而对于特殊的激光沉积修复-激光复合制造来说,由于激光复合制造涉及锻造等传统制造和激光沉积制造两部分,因此组织上出现较大差异,因此采用β相区淬火处理+循环热处理+退火处理对激光复合制造的显微组织进行调节和均匀化。通过观察发现,α相受力变形机制与α相的形貌、含量和所处的位置有关。不同的热处理温度以及热处理方式得到的α相形貌不同,不同形貌尺寸和位置的α相具有不同的受力变形机制,网篮状α相、片层状α相以及α团束受力变形机制均不相同,柱状晶晶内α相和柱状晶晶界两侧α相的受力变形机制存在差异。激光沉积修复TA15钛合金基材、热影响区以及修复区的组织不同,造成出现不同的受力变形机制。β相区淬火处理+循环热处理+退火处理能够减小激光复合制造TA15钛合金沉积部分和基体部分的组织差异性,组织整体上趋近于一致。
[Abstract]:Based on the idea of "discrete stacking", laser deposition technology uses coaxial powder feeding and laser cladding digital forming to further control the forming accuracy of workpiece. However, due to the high density energy accumulation of laser and the singularity of heat dissipation direction in the forming process, the microstructure distribution of the formed parts is not uniform. The mechanical properties are anisotropic. The heat treatment process has the functions of adjusting microstructure and improving mechanical properties. Therefore, the heat treatment process is applied to laser deposition to make forming parts. Because of the particularity of laser deposition manufacturing technology, As a result, the microstructure of the process is obviously different from that of the traditional forging or casting methods, and the heat treatment process needs to be rediscovered and developed. The laser deposition manufacturing technology includes laser deposition manufacturing and laser deposition repair. For laser deposition of TA15 titanium alloy, because the temperature of 伪尾 phase region is large, the annealing experiments with different temperature gradient are carried out in the 伪尾 phase region. The effect of annealing temperature in 伪尾 phase region on the microstructure and tensile mechanical properties at room temperature was studied, and the heat treatment temperature was further refined in the temperature range where the microstructure was uniform and the mechanical properties were better. Secondly, double annealing experiments were carried out in the 伪尾 and 尾 phase regions to study the effect of double annealing on microstructure and anisotropy of mechanical properties. For laser deposition and repair of TA15 titanium alloy, the stability of matrix structure should be guaranteed during heat treatment. Therefore, the effects of heat treatment on microstructure and mechanical properties under different repair methods are mainly investigated, while for special laser deposition repair and laser composite manufacturing, Because laser composite manufacturing involves traditional manufacturing such as forging and laser deposition, there is a great difference in structure. Therefore, the microstructure of laser composite was adjusted and homogenized by the treatment of 尾 phase quenching and cyclic heat treatment and annealing. It was found that the mechanical deformation mechanism of 伪 phase and the morphology of 伪 phase were observed. The content of 伪 phase is related to the location of the phase. The morphology of 伪 phase is different with different heat treatment temperature and heat treatment method. The deformation mechanism of 伪 phase with different morphologies and positions is different. The deformation mechanism of lamellar 伪 phase and 伪 cluster beam is different, and the deformation mechanism of 伪 phase in columnar crystal is different from that of 伪 phase on both sides of columnar grain boundary. Laser deposition is used to repair TA15 titanium alloy substrate. The microstructure of the heat-affected zone and the repair zone are different, resulting in different deformation mechanisms. The microstructure difference between the deposition part and the matrix part of the TA15 alloy can be reduced by the cyclic heat treatment and annealing treatment in the 尾 phase region, which can reduce the microstructure difference between the deposited part and the matrix part of the TA15 titanium alloy fabricated by laser. The organization as a whole is in line.
【学位授予单位】：沈阳航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG665;TG166.5

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