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    热处理工艺对激光熔覆Ti-10V-2Al-3Fe合金粉末修复Ti-6Al-4V合金组织和性能的影响

    Effect of Heat Treatment Process on Microstructure and Properties of Ti-6Al-4V Alloy Repaired by Laser Cladding Ti-10V-2Al-3Fe Alloy Powder

    • 摘要: 采用激光熔覆Ti-10V-2Al-3Fe合金粉末的方法对轧制态Ti-6Al-4V合金表面进行修复,分别进行650 ℃×2 h退火和750 ℃×2 h固溶+510 ℃×8 h时效处理,研究了热处理工艺对试样不同区域显微组织、硬度和拉伸性能的影响。结果表明:沉积态激光熔覆层组织由原始柱状β晶粒以及β晶粒内部的网篮状α相组成,热影响区组织为过饱和针状马氏体;退火后熔覆层的部分网篮组织长大,部分层片状α相转化为等轴α相,热影响区中马氏体减少,形成弥散的(α+β)相,原始组织为片状α相延伸晶粒和β晶界的基体中出现α等轴晶;与退火态相比,固溶时效态激光熔覆层部分网篮组织进一步长大,更多层片状α相转化为等轴α相,热影响区中马氏体进一步减少,基体中出现更多α等轴晶。退火和固溶时效处理降低了激光熔覆层的硬度,对基体和热影响区的总体硬度影响不大。退火处理后基体和激光熔覆层的抗拉强度和屈服强度降低,断后伸长率提高;固溶时效处理使得基体强度降低,断后伸长率提高,使得激光熔覆层强度和断后伸长率同步提高。经750 ℃×2 h固溶和500 ℃×8 h时效处理后试样的综合力学性能最好,基体和激光熔覆层的硬度分别为349,373 HV,抗拉强度分别为888,1 003 MPa,断后伸长率分别为22.1%和20.9%。

       

      Abstract: The surface of the rolled Ti-6Al-4V alloy was repaired by laser cladding of Ti-10V-2Al-3Fe alloy powder. The samples after laser cladding were subjected to annealing at 650 ℃ for 2 h and to solution at 750 ℃ for 2 h + aging at 510 ℃ for 8 h separately. The influence of the heat treatment process on the microstructure, hardness and tensile properties of different regions of the samples was studied. The results show that the microstructure of the as-deposited cladding layer was composed of original columnar β grains and net-like α phases within the β grains, and the microstructure of the heat-affected zone was supersaturated acicular martensite. After annealing, a part of the net-like structures in cladding layer grew, some lamellar α phases transformed into equiaxed α phases; the martensite in the heat-affected zone decreased, forming dispersed (α+β) phases; α equiaxed grains appeared in the substrate with an original structure composed of lamellar α phase extension grains and β grain boundaries. Compared with those in the annealed state, the partial net-like structure of the laser cladding layer in the solution aged state further grew, and more layers of α phase transformed into equiaxed α phase; the martensite in the heat-affected zone further decreased, and more α equiaxed crystals appeared in the substrate. The annealing and solution aging treatment decreased the hardness of the laser cladding layer, but had little effect on the overall hardness of the substrate and the heat-affected zone. After annealing, the tensile strength and yield strength of the substrate and the cladding layer decreased, while the percentage elongation after fracture increased. The solution aging treatment made the strength of the substrate decrease while the percentage elongation after fracture increase, and made the strength and the percentage elongation after fracture of the cladding layer increase. The comprehensive mechanical properties of the sample after 750 ℃× 2 h solid solution and 500 ℃× 8 h aging were the best. The hardness of the substrate and laser cladding layer was 349, 373 HV, the tensile strength was 888,1 003 MPa, and the percentage elongation after fracture was 22.1% and 20.9%, respectively.

       

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