本文選題：Ti-6Al-4V合金　切入點：微弧氧化　出處：《南昌航空大學》2017年碩士論文　論文類型：學位論文

【摘要】：在8g/L Na_2SiO_3·9H_20-6g/L(NaPO_3)_6-4g/L Na_2WO_4·2H_2O-2g/L Na5P3O10電解液體系中,采用直流脈沖模式,以電流密度為10A/dm2,頻率為500HZ,占空比為50%的電參數(shù)對TC4鈦合金進行微弧氧化。通過第二相顆粒(β-SiC、γ-Al_2O_3、κ-Al_2O_3、m-ZrO_2)的相變和分解探索了熔池溫度;并通過第二相顆粒的分布尋找放電通道;首次通過長距離顯微鏡觀察了火花和熔池的對應關系;探索了TC4鈦合金微弧氧化膜的生長方式及成膜機理與模型。研究結果表明:氧化電壓是微弧氧化膜層生長的驅動力。微弧氧化前10min電壓隨時間的增長速率明顯高于10-120min。前十分鐘電壓隨時間的變化呈Logistic S型指數(shù)曲線遞增規(guī)律,10min-120min內(nèi)電壓隨時間呈低斜率線性變化規(guī)律,方程為:(1)V=541.2749-571.9594/(1+t/1.49761)~(1.10423)(0t10min)(2)V=486.83797+0.2615t(10≤t120min)膜層厚度、粗糙度及熔池尺寸隨終止電壓的增加而增加,熔池的尺寸隨著膜層厚度的增加服從二次多項式y(tǒng)=-114.99725+7.85254x-0.06728x~2,其中x為膜層厚度,y為熔池尺寸。通過γ-Al_2O_3、κ-Al_2O_3、m-ZrO_2的相變,β-SiC的相變及分解判定微弧氧化過程中熔池溫度分布不均,存在一個溫度范圍:最低溫度小于1223K,最高溫度大于3143K。氧化過程中,火花和熔池呈一一對應的關系,隨著微弧氧化的進行,火花擊穿膜層產(chǎn)生熔池,火花尺寸與熔池尺寸的變化規(guī)律一致,都在不斷增大,兩者尺寸相當,但熔池的尺寸略小于火花尺寸。隨著氧化時間的增加,火花密度不斷減少,火花持續(xù)的時間不斷增加。電壓快速增長階段、電壓轉折階段、電壓穩(wěn)定增長階段的火花尺寸分別為9.9μm、23.8925μm、108.46μm,熔池的直徑分別為12.645μm、28.84μm、112.56μm,火花密度分別為132個/cm~2、18個/cm~2、4個/cm~2,火花持續(xù)的時間分別為0.07s、0.55s、3.315s。微弧氧化成膜過程中,膜層與基體是通過犬牙交錯方式結合的,在膜層與基體的交界面,能明顯觀察到放電通道的存在,尺寸約為0.6nm。微弧氧化過程中火花等離子體對膜層的擊穿首先發(fā)生在膜層的薄弱處,放電類型分為三種,分別發(fā)生在膜層表面,膜基交界面,膜層中間�；鸹▽δ拥膿舸┓绞绞黔h(huán)環(huán)相扣式擊穿,火花沿放電通道放電直達基體,使熔融基體和氧化物沿放電通道火山式噴發(fā)、流淌,并在電解液驟冷作用下凝固,從而使新舊熔池不斷翻新重組,近而使膜層通過熔池重組的方式進行生長。微弧氧化成膜模型為圖5-8e。
[Abstract]:In the system of 8g / L Na_2SiO_3 路9H S / L / 20 ~ 6g / L / L Na_2SiO_3 / T / T _ 6-4g / L Na_2WO_4 路2H _ 2O-2g / L Na5P3O10 electrolyte, the phase transition and decomposition temperature of the TC4 titanium alloy was investigated by the phase transition and decomposition of the second phase particle (尾 -SiC, 緯 -Al2O3, 魏 -Al2O3mZrO2) with electric parameters of current density of 10A / dm2, frequency of 500HZ, duty cycle ratio of 50%. The phase transition and decomposition of TC4 titanium alloy were investigated by means of the second phase particle (尾 -SiC, 緯 -Al2O3, 魏 -Al2O3ZrO2). The discharge channel was found by the distribution of the second phase particles, and the corresponding relationship between the spark and the molten pool was observed by the long distance microscope for the first time. The growth mode, film forming mechanism and model of TC4 titanium alloy microarc oxide film were studied. The results show that the oxidation voltage is the driving force of the micro arc oxide film growth. The change of voltage with time in the first ten minutes was an increasing rule of exponential curve of Logistic S-type, and the voltage changed linearly with time at a low slope in 10 min-120 min. The equation is that the thickness of the film, the roughness and the size of the melting pool increase with the increase of the termination voltage. With the increase of the thickness of the coating, the size of the molten pool is changed from the quadratic polynomial y1-114.99725 7.85254x-0.06728xm2, in which x is the thickness of the film, and y is the size of the molten pool. The phase transition of 緯 -AlAl2O3, 魏 -AlSn2O3- ZrOSn2, the phase transition of 尾 -SiC and the decomposition of 尾 -SiC are used to determine the uneven temperature distribution of the molten pool in the process of micro-arc oxidation. There is a temperature range: the lowest temperature is less than 1223K, and the highest temperature is more than 3143k.in the oxidation process, the relationship between the spark and the molten pool is one-to-one. With the development of micro-arc oxidation, the spark breaks through the film layer to produce the molten pool. The size of the spark and the size of the weld pool are all increasing, but the size of the pool is slightly smaller than the size of the spark, and the density of the spark decreases with the increase of the oxidation time. The duration of sparks continues to increase. The period of rapid voltage growth, the phase of voltage transition, The spark size of the voltage stable growth stage is 9.9 渭 m ~ 23.8925 渭 m ~ (-1) 108.46 渭 m, the diameter of the melting pool is 12.645 渭 m ~ (28. 84) 渭 m ~ (-1), the spark density is 132 / cm ~ (2), 18 / cm ~ (2), 4 cm / m ~ (2), and the duration of the spark is 0.07 s-1 ~ (0.55) s ~ (3) ~ (315) s, respectively. In the interface between the film and the substrate, the discharge channel can be observed obviously. In the process of micro-arc oxidation, the breakdown of the film by spark plasma first occurs in the weak part of the film, and the discharge type is divided into three types, which occur on the surface of the film and at the interface between the film and the substrate, respectively. In the middle of the film layer. The way of the spark breakdown to the film is the annular breakdown, the spark discharge along the discharge channel to the matrix, so that the molten matrix and the oxide erupt along the discharge channel, flow, and solidify under the action of electrolyte sudden cooling. Thus, the new and old molten pools are continuously renovated and reorganized, and the film layer is grown through the recombination of the molten pool. The model of micro-arc oxidation film formation is shown in figure 5-8 e.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG174.4

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