發(fā)布時間：2018-05-08 18:03

  本文選題：激光熔化沉積 + AlSi10Mg��； 參考：《南京航空航天大學(xué)》2017年碩士論文

【摘要】：隨著航空航天技術(shù)的發(fā)展,鋁合金結(jié)構(gòu)件向著大型化、整體化、形狀復(fù)雜化、薄壁化、高精化的方向發(fā)展。激光熔化沉積技術(shù)是一種新興金屬增材制造技術(shù),成本低、材料利用率高、加工周期短等技術(shù)優(yōu)點使其在航空航天領(lǐng)域有廣泛的應(yīng)用前景。但是鋁合金自身對激光吸收率較低、導(dǎo)熱系數(shù)過大、粉末流動性差等特點給其進行激光熔化沉積成形工藝帶來了很大的挑戰(zhàn)。本文闡述了激光熔化沉積技術(shù)的工藝特點及原理,采用理論與試驗相結(jié)合的方法對激光熔化沉積AlSi10Mg合金的可行性、成形工藝及組織性能進行了基礎(chǔ)研究,所完成的主要工作如下:(1)驗證了激光熔化沉積成形AlSi10Mg合金的可行性。采用激光熔化沉積技術(shù)可以成功制備出具有快速凝固致密組織特征的沉積試樣,例如條狀沉積塊、薄壁箱體等。(2)探究了激光功率P和掃描速度V_s對激光熔化沉積單道形貌的影響規(guī)律。在一定的工藝范圍內(nèi),沉積層寬度、熔深隨著功率的增大而增大,隨著掃描速度的增大而減小,且發(fā)現(xiàn)鋁合金沉積過程中基體的熱累積對沉積形貌有著顯著的影響。(3)提出鋁合金激光熔化沉積基體熱累積的表征方法。結(jié)合熱場仿真和沉積紅外熱成像結(jié)果,定義基體熱累積因子X_R來表征基體熱累積量,并建立簡化的數(shù)學(xué)模型。隨著熱累積量的增加,沉積層寬度、熔深逐漸變大,沉積層高度的變化較小。接觸角θ、稀釋率η與X_R呈線性相關(guān),接觸角θ隨著X_R的的增大而減小,稀釋率η隨著X_R的的增大而增大。(3)分析了激光熔化沉積AlSi10Mg合金試樣的相組成和顯微組織演變特點。AlSi10Mg沉積態(tài)試樣中主要相成分為α-Al相、共晶Si及少量的Mg_2Si強化相。顯微組織為連續(xù)外延生長的定向柱狀晶組織,在最上面的沉積層頂部逐漸轉(zhuǎn)變?yōu)榈容S晶,沉積層之間呈現(xiàn)出層帶特點。沉積態(tài)AlSi10Mg的屈服強度達到183.65MPa,顯微硬度達到100~130HV。(4)研究了熱處理工藝對AlSi10Mg合金沉積試樣組織和性能的影響�！肮倘�+時效”工藝可以有效提高AlSi10Mg合金沉積試樣的屈服強度,熱處理后的沉積試樣組織中Si相的珊瑚桿狀分枝基本消失,共晶Si相以分散圓形粒狀形貌存在,試樣屈服強度達到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 偽 -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.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.21

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