【摘要】：空化發(fā)生在液體內(nèi)部,與液體壓強(qiáng)的變化息息相關(guān),是空泡初生、長大與潰滅的過程�？瘴g是空化對固體材料造成的損傷與破壞,是空化的結(jié)果。對于工作在液體環(huán)境下的液壓元件、水利設(shè)施等,在液體壓強(qiáng)變化時(shí),表面材料容易受到空蝕的作用。AlSi10Mg材料具備耐磨損侵蝕、熱膨脹系數(shù)低、強(qiáng)度與剛度高、導(dǎo)熱性好等優(yōu)點(diǎn),應(yīng)用十分廣泛,但對其空蝕性能的研究還相對較少。基于AlSi10Mg材料在液體環(huán)境下的應(yīng)用背景,有必要對其空蝕性能展開研究。本文各章內(nèi)容分述如下第一章,介紹了空化、空蝕的物理背景以及基于空化射流的材料空蝕性能標(biāo)準(zhǔn)實(shí)驗(yàn),介紹了表面形貌對于空蝕的影響規(guī)律與機(jī)理,介紹了選擇性激光熔化(SLM)技術(shù)及在鋁合金上的研究與應(yīng)用背景,最終確定了論文研究內(nèi)容。第二章,以ASTMG134為標(biāo)準(zhǔn),搭建了空化射流實(shí)驗(yàn)平臺,并加工制造了符合標(biāo)準(zhǔn)的空化射流噴嘴,為空蝕實(shí)驗(yàn)的進(jìn)行奠定實(shí)驗(yàn)裝置的基礎(chǔ),另外結(jié)合表面形貌、硬度測試、密度測試、物相分析、金相分析等手段,介紹了相關(guān)實(shí)驗(yàn)設(shè)備。第三章,探究不同表面加工方式(激光織構(gòu)、車削、磨削和拋光)造成的原始表面形貌差異對于鍛造AlSi10Mg試件空蝕性能的影響,發(fā)現(xiàn):表面更粗糙的激光織構(gòu)試件和車削試件的質(zhì)量損失大于其他兩種試件;在具有一種類似形貌特征的激光織構(gòu)試件和車削試件表現(xiàn)出水平方向上的塑性變形,其他兩種試件沒有出現(xiàn)這種現(xiàn)象;通過兩種三維表面高度參數(shù),可以預(yù)測表面加工痕跡受空蝕作用后消失的時(shí)間。第四章,探究選擇性激光熔化(SLM)過程中不同的激光掃描速度對SLM試件空蝕性能的影響,并與鍛造試件做出對比,發(fā)現(xiàn):SLM試件在加速階段的質(zhì)量損失遠(yuǎn)大于鍛造試件,這主要是由于SLM試件表面的氣孔缺陷和氣孔內(nèi)的殘余合金顆粒造成的,過快或者過慢的激光掃描速度會加大氣孔的尺寸和殘余合金顆粒的數(shù)量,導(dǎo)致空蝕加速階段中更大的質(zhì)量損失及速率;進(jìn)入穩(wěn)定期后,三種選擇性激光熔化試件的質(zhì)量損失速率遠(yuǎn)遠(yuǎn)小于鍛造試件,但選擇性激光熔化試件之間差別不大,激光掃描速度對其影響基本可忽略不計(jì);SLM試件顯微金相表現(xiàn)為樹枝狀的Si相將A1基體分割為小島狀,這種組織均勻、晶粒細(xì)小的結(jié)構(gòu)提高了 SLM試件的硬度和抗空蝕能力。第五章,總結(jié)了本文主要研究工作與成果,展望了今后有待進(jìn)一步開展的研究內(nèi)容。
[Abstract]:Cavitation occurs in the liquid and is closely related to the change of liquid pressure. It is the process of cavitation, growth and collapse. Cavitation erosion is the result of cavitation and damage to solid material caused by cavitation. For hydraulic components and water conservancy facilities working in liquid environment, when the liquid pressure changes, the surface material is vulnerable to cavitation erosion. AlSi10mg material has the advantages of abrasion resistance, low thermal expansion coefficient, high strength and stiffness, good thermal conductivity, etc. It is widely used, but the study of cavitation corrosion performance is relatively rare. Based on the application background of AlSi10Mg material in liquid environment, it is necessary to study its cavitation corrosion property. In the first chapter, the physical background of cavitation and cavitation erosion and the standard experiment of cavitation performance based on cavitation jet are introduced, and the influence law and mechanism of surface morphology on cavitation erosion are introduced. The selective laser melting (SLM) technology and its research and application background on aluminum alloy are introduced. Finally, the research content of this paper is determined. In the second chapter, the cavitation jet experimental platform is set up with ASTMG134 as the standard, and the cavitation jet nozzle is manufactured according to the standard, which lays the foundation of the experimental device for the cavitation corrosion experiment. In addition, it combines the surface morphology, hardness test and density test. The related experimental equipment is introduced by means of phase analysis and metallographic analysis. In chapter 3, the effects of different surface processing methods (laser textures, turning, grinding and polishing) on the cavitation corrosion properties of forged AlSi10Mg specimens are investigated. It is found that the mass loss of the laser textured and turning specimens with rougher surface is larger than that of the other two, and that the laser texture and turning specimens with a similar morphologic feature exhibit a horizontal plastic deformation. There is no such phenomenon in the other two kinds of specimens, and the time of surface machining trace disappearing after cavitation erosion can be predicted by two three dimensional surface height parameters. In chapter 4, the effects of different laser scanning speeds on the cavitation corrosion properties of SLM specimens during the selective laser melting process are investigated, and compared with the forged specimens, it is found that the mass loss of the SLM specimens at the acceleration stage is much greater than that of the forged specimens. This is mainly due to the porosity defects on the surface of SLM specimens and the residual alloy particles in the pores. Too fast or too slow laser scanning speed will increase the size of the pores and the number of residual alloy particles. The mass loss rate of the three kinds of selective laser melting specimen is much smaller than that of the forged specimen, but the difference between the three selective laser melting specimens is not significant. The effect of laser scanning speed on the microstructure of SLM specimens is negligible. The microstructure of SLM specimens is characterized by dendritic Si phase, which divides A1 matrix into small islands. The microstructure of the samples is uniform and the fine grain structure improves the hardness and cavitation resistance of SLM specimens. In the fifth chapter, the main research work and results are summarized, and the future research contents are prospected.
【學(xué)位授予單位】：浙江大學(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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