本文關(guān)鍵詞：超聲輔助激光熔注復(fù)合涂層晶粒生長研究　出處：《華東交通大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 激光熔注 元胞自動機法 超聲振動 增強顆粒 晶粒生長

【摘要】：超聲輔助激光熔注技術(shù)是制備高性能復(fù)合涂層的理想方法之一，在航空航天、交通運輸?shù)阮I(lǐng)域具有廣泛的應(yīng)用前景。涂層微觀結(jié)構(gòu)對其服役性能起決定作用，因此研究超聲輔助激光熔注復(fù)合涂層微觀結(jié)構(gòu)具有重要意義。 本文采用元胞自動機法研究了激光熔注復(fù)合涂層的晶粒生長，分析了增強顆粒、非均勻溫度場以及超聲振動對復(fù)合涂層晶粒生長的影響。基于晶界能和曲率驅(qū)動機制的晶粒生長理論，建立了單相材料及兩相材料晶粒生長元胞自動機模型，分析了增強相SiC顆粒對316L不銹鋼復(fù)合涂層和AZ91D基板晶粒生長的影響，研究了超聲輔助激光熔注復(fù)合涂層微觀結(jié)構(gòu)的演變機制，并對其進行了實驗驗證。得出以下結(jié)論： （1）316L晶粒生長指數(shù)為0.34，，隨SiC含量增大和尺寸減小，涂層晶粒尺寸減�。浑S著熔池深度變化，熔池溫度呈指數(shù)函數(shù)變化，晶粒尺寸逐漸增大。在非均勻溫度場下，隨SiC顆粒含量增加，其對晶界的釘扎效果逐漸增強；隨著SiC顆粒尺寸減小，釘扎效果增強，但是，當(dāng)SiC顆粒尺寸小于10μm時，晶粒細(xì)化機制由晶界釘扎轉(zhuǎn)變?yōu)楫愘|(zhì)形核。 （2）隨著SiC顆粒加入，鎂合金基板的晶粒生長速率變緩，晶粒尺寸變小且均勻；隨著SiC尺寸減小，其對基板組織的釘扎效果增強，基板晶粒越細(xì)小，組織越均勻，Mg17Al12相越易固溶于α-Mg基體中。 （3）隨著超聲振幅的增大，涂層熔體形核率增大，晶粒尺寸變小，組織越均勻。當(dāng)振幅為10μm時，超聲振動作用下熔體的過冷度為32.23K，形核率為未施加超聲振動時的279倍，晶粒細(xì)化明顯。在超聲輔助激光熔注SiC-316L實驗中，涂層中SiC顆粒含量越大，涂層晶粒越細(xì)小，組織越均勻；SiC顆粒尺寸越小，其對涂層組織的釘扎效果越好，施加超聲后的316L涂層組織柱狀枝晶更少，晶粒更細(xì)小，模擬結(jié)果與實驗結(jié)果吻合。
[Abstract]:Ultrasonic assisted laser melting technology is one of the ideal methods for preparing high performance composite coatings. It has a wide application prospect in aerospace, transportation and other fields. The microstructure of the coating plays a decisive role in its service performance. Therefore, it is of great significance to study the microstructure of ultrasonic assisted laser fusion composite coatings. In this paper, the grain growth of laser fused composite coating was studied by cellular automata method, and the reinforced particles were analyzed. The effect of non-uniform temperature field and ultrasonic vibration on the grain growth of composite coatings was studied. Based on the grain growth theory of grain boundary energy and curvature driven mechanism, the cellular automata model of grain growth for single-phase and two-phase materials was established. The effect of reinforced SiC particles on the grain growth of 316L stainless steel composite coating and AZ91D substrate was analyzed, and the evolution mechanism of ultrasonic assisted laser melt composite coating microstructure was studied. The following conclusions are obtained: The grain growth index is 0.34, and the grain size decreases with the increase of SiC content and the decrease of grain size. With the change of the depth of the molten pool, the temperature of the molten pool changes as an exponential function, and the grain size increases gradually. Under the inhomogeneous temperature field, the effect of pinning on the grain boundary increases with the increase of the content of SiC particles. The pinning effect increases with the decrease of SiC particle size. However, when SiC particle size is less than 10 渭 m, the grain refinement mechanism changes from grain boundary pinning to heterogeneous nucleation. (2) with the addition of SiC particles, the grain growth rate of magnesium alloy substrate becomes slower, and the grain size becomes smaller and more uniform; With the decrease of the size of SiC, the effect of pinning on the substrate structure is enhanced. The smaller the grain size of the substrate is, the more homogeneous the microstructure of Mg17Al12 phase is, and the easier it is to dissolve in 偽 -Mg matrix. 3) with the increase of ultrasonic amplitude, the nucleation rate of the melt increases, the grain size becomes smaller and the microstructure becomes more uniform. When the amplitude is 10 渭 m, the undercooling degree of the melt under ultrasonic vibration is 32.23 K. The nucleation rate is 279 times of that without ultrasonic vibration, and the grain refinement is obvious. In the SiC-316L experiment of ultrasonic assisted laser melting, the larger the content of SiC particles in the coating is, the smaller the grain size of the coating is. The more homogeneous the tissue is; The smaller the particle size of SiC is, the better the pinning effect of the coating is, and the smaller the columnar dendrite and the finer the grain of 316L coating after ultrasonic application, the simulation results are in good agreement with the experimental results.
【學(xué)位授予單位】：華東交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN249

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