激光熔化沉积成形AlSi10Mg合金的工艺与组织性能研究

发布时间：2018-05-08 18:03

本文选题：激光熔化沉积 + AlSi10Mg　；参考：《南京航空航天大学》2017年硕士论文

【摘要】：随着航空航天技术的发展,铝合金结构件向着大型化、整体化、形状复杂化、薄壁化、高精化的方向发展。激光熔化沉积技术是一种新兴金属增材制造技术,成本低、材料利用率高、加工周期短等技术优点使其在航空航天领域有广泛的应用前景。但是铝合金自身对激光吸收率较低、导热系数过大、粉末流动性差等特点给其进行激光熔化沉积成形工艺带来了很大的挑战。本文阐述了激光熔化沉积技术的工艺特点及原理,采用理论与试验相结合的方法对激光熔化沉积AlSi10Mg合金的可行性、成形工艺及组织性能进行了基础研究,所完成的主要工作如下:(1)验证了激光熔化沉积成形AlSi10Mg合金的可行性。采用激光熔化沉积技术可以成功制备出具有快速凝固致密组织特征的沉积试样,例如条状沉积块、薄壁箱体等。(2)探究了激光功率P和扫描速度V_s对激光熔化沉积单道形貌的影响规律。在一定的工艺范围内,沉积层宽度、熔深随着功率的增大而增大,随着扫描速度的增大而减小,且发现铝合金沉积过程中基体的热累积对沉积形貌有着显著的影响。(3)提出铝合金激光熔化沉积基体热累积的表征方法。结合热场仿真和沉积红外热成像结果,定义基体热累积因子X_R来表征基体热累积量,并建立简化的数学模型。随着热累积量的增加,沉积层宽度、熔深逐渐变大,沉积层高度的变化较小。接触角θ、稀释率η与X_R呈线性相关,接触角θ随着X_R的的增大而减小,稀释率η随着X_R的的增大而增大。(3)分析了激光熔化沉积AlSi10Mg合金试样的相组成和显微组织演变特点。AlSi10Mg沉积态试样中主要相成分为α-Al相、共晶Si及少量的Mg_2Si强化相。显微组织为连续外延生长的定向柱状晶组织,在最上面的沉积层顶部逐渐转变为等轴晶,沉积层之间呈现出层带特点。沉积态AlSi10Mg的屈服强度达到183.65MPa,显微硬度达到100~130HV。(4)研究了热处理工艺对AlSi10Mg合金沉积试样组织和性能的影响。“固溶+时效”工艺可以有效提高AlSi10Mg合金沉积试样的屈服强度,热处理后的沉积试样组织中Si相的珊瑚杆状分枝基本消失,共晶Si相以分散圆形粒状形貌存在,试样屈服强度达到237.61MPa。
[Abstract]:With the development of aeronautics and astronautics, aluminum alloy structure is developing towards large scale, integrated, complicated shape, thin wall and high precision. Laser melting deposition technology is a new technology for manufacturing metal materials, which has the advantages of low cost, high material utilization rate and short processing cycle, so it has a wide application prospect in the field of aeronautics and astronautics. However, the low laser absorptivity, excessive thermal conductivity and poor powder fluidity of aluminum alloy bring great challenge to laser melt deposition process. In this paper, the technological characteristics and principle of laser melting deposition technology are described. The feasibility, forming process, microstructure and properties of laser melting deposition AlSi10Mg alloy are studied by combining theory and experiment. The main work is as follows: 1) the feasibility of laser melt deposition for forming AlSi10Mg alloy is verified. By using laser melting deposition technology, deposited samples with rapid solidification and compact microstructure, such as stripe deposition, can be successfully prepared. The influence of laser power P and scanning velocity VSTs on the single channel morphology of laser melt deposition was investigated. In a certain process range, the width and penetration of the deposit increase with the increase of power and decrease with the increase of scanning speed. It is also found that the thermal accumulation of the substrate has a significant effect on the deposition morphology during the deposition of aluminum alloy. (3) A method to characterize the thermal accumulation of the aluminum alloy substrate by laser melting deposition is proposed. Based on the thermal field simulation and deposition infrared imaging results, the matrix thermal accumulation factor (XAR) is defined to characterize the matrix thermal accumulation, and a simplified mathematical model is established. With the increase of heat accumulation, the width and penetration of the deposit become larger, and the height of the deposit changes slightly. The contact angle 胃 and dilution ratio 畏 are linearly correlated with Xs, and the contact angle 胃 decreases with the increase of XR. The phase composition and microstructure evolution characteristics of laser-melted deposited AlSi10Mg alloy samples were analyzed. The main phase components in the deposited samples of AlSi10mg were 伪 -Al, eutectic Si and a small amount of Mg_2Si strengthened phase. The microstructure is a directionally columnar structure grown by continuous epitaxy, which is gradually transformed into equiaxed crystals at the top of the top of the deposit layer, and shows the characteristics of laminar zone between the deposits. The effect of heat treatment on the microstructure and properties of deposited AlSi10Mg alloy was studied. The yield strength and microhardness of the deposited AlSi10Mg were 183.65 MPA and 100,130HV. / 4 respectively. The "solid solution aging" process can effectively improve the yield strength of the deposited samples of AlSi10Mg alloy. After heat treatment, the coral rod-like branching of Si phase in the microstructure of the deposited sample is basically disappeared, and the eutectic Si phase exists in the shape of dispersed circular particles. The yield strength of the specimen is 237.61 MPA.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21

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