本文選題：選區(qū)激光熔化 + 合金粉末��； 參考：《蘭州理工大學(xué)》2017年碩士論文

【摘要】：選區(qū)激光熔化技術(shù)(Selective Laser Melting,SLM)是近年來出現(xiàn)的一種新型的快速制造技術(shù)。通過此種技術(shù)所制造的零件廣泛應(yīng)用于國防工業(yè)、航空航天、模具機械和個性化定制等領(lǐng)域。由于國內(nèi)起步相對較晚,在選區(qū)激光熔化技術(shù)方面我國與發(fā)達國家還有一定的差距,目前,高質(zhì)量選區(qū)激光熔化金屬粉末主要依賴進口,國外廠商常將原材料與設(shè)備捆綁高價銷量,極大地制約了我國的金屬選區(qū)激光熔化技術(shù)的發(fā)展;而且國內(nèi)外學(xué)者對于選區(qū)熔化的研究大多集中在激光工藝參數(shù)及某種金屬粉末成型的機械性能等方面,對于粉末粒度分布等特性的研究較少。因此,本文以SLM專用GH4169,GH3625,316L合金粉末為例,進行選區(qū)激光熔化粉末的特性及成型件組織結(jié)構(gòu)的研究,通過大量試驗得出最佳工藝,以期為金屬粉末制備及成型工藝的優(yōu)化提供有益指導(dǎo)。在粉末為同一批次的情況下,詳細研究了GH4169的粉末粒徑分布,通過大量的成型試驗,結(jié)果表明:粒度過小、粉末易團聚,鋪粉過程中易出現(xiàn)波浪紋,不能形成平整均勻的選區(qū)熔化平面,不適合成型件的制備;粒度過大,會增加粉末顆粒與顆粒之間的孔隙,在快速熔化與冷卻的過程中液體不能充分的填充孔隙易造成孔洞;粒度在15-53μm之間,平均粒徑約為32μm左右的粉末,進行選區(qū)熔化之后可以得到高質(zhì)量的成型件,經(jīng)過金相腐蝕觀察可知其內(nèi)部組織呈現(xiàn)胞狀結(jié)晶形態(tài),“微熔池”內(nèi)的“亞微米長柱狀晶”(亞晶)由于溫度場復(fù)雜多變的影響,也顯示出了多種不同的結(jié)晶形貌,通過對拉伸件的測試得出其延伸率為36.3%、屈服強度929Mpa、抗拉強度1058Mpa左右,顯示出了良好的拉伸性能,斷裂方式為韌性斷裂與解理斷裂的混合斷裂;通過GH4169得出的試驗結(jié)果,將粉末的粒度分配比例運用到GH3625與316L粉末的生產(chǎn)與篩分上,通過成型試驗可以得到性能良好的成型件,對適于選區(qū)激光熔化粉末的生產(chǎn)提供了一定的指導(dǎo)作用,經(jīng)過金相分析可知,GH3625、316L與GH4169的結(jié)晶形貌一致,組織均為胞狀晶,由于材料成分以及工藝的影響“微熔池”內(nèi)部“亞微米長柱狀晶”的直徑、位向分布均有所不同,GH3625與316L的斷裂方式為韌性斷裂。通過本文的試驗結(jié)果,與一些企業(yè)聯(lián)合進行粉末的試制,在經(jīng)過粉末的篩分與級配之后,經(jīng)過選區(qū)激光熔化,得到了外觀漂亮,成型效果良好的產(chǎn)品。
[Abstract]:Selective Laser melting (SLM) is a new rapid manufacturing technology. The parts manufactured by this technology are widely used in the fields of defense industry, aerospace, mould machinery and personalized customization. Due to the relatively late start in China and the gap between China and the developed countries in the area of selective laser melting technology, at present, the high quality selective laser melting metal powder mainly depends on imports. Foreign manufacturers often bundle the raw materials and equipment to sell at a high price, which greatly restricts the development of laser melting technology in our country. Moreover, the researches on selective melting mostly focus on laser processing parameters and mechanical properties of a certain metal powder, but few on the properties of particle size distribution. Therefore, taking GH4169 / GH3625316L alloy powder for SLM as an example, the characteristics of selected laser melting powder and the microstructure of molded parts are studied. The optimum process is obtained through a large number of experiments. In order to provide useful guidance for metal powder preparation and optimization of molding process. In the case of the same batch of powder, the particle size distribution of GH4169 powder is studied in detail. The results show that the particle size is too small, the powder is easy to agglomerate, and the wavy grain is easy to appear in the process of powder laying. If the particle size is too large, the porosity between powder particles and particles will be increased, and in the process of rapid melting and cooling, the porosity will be easily caused by the insufficient filling of the pores in the process of rapid melting and cooling. When the particle size is 15-53 渭 m and the average particle size is about 32 渭 m, high quality molded parts can be obtained after selective melting. The "submicron columnar crystal" (sub-crystal) in the "micromelting pool" also shows many different crystal morphologies due to the complex and changeable temperature field. The elongation ratio is 36.3%, yield strength is 929 MPA, tensile strength is about 1058Mpa, which shows good tensile properties, the fracture mode is the mixed fracture of ductile fracture and cleavage fracture, and the test results obtained by GH4169 show that the tensile strength is about 929MPA, and the tensile strength is about 1058Mpa. The granularity distribution ratio of the powder is applied to the production and screening of GH3625 and 316L powder, and the forming parts with good properties can be obtained by forming test, which provides some guidance for the production of selected laser melted powder. Metallographic analysis shows that the crystal morphology of GH3625316L is the same as that of GH4169, and the microstructures are all cellular crystals. The diameter of "sub-micron columnar crystals" in the "micro-melting pool" is affected by the composition of the material and the process. The fracture mode of GH3625 and 316L is ductile fracture. According to the experimental results of this paper, the powder was produced in combination with some enterprises. After the powder was sifted and graded, the products with beautiful appearance and good forming effect were obtained by selective laser melting.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TF124.3;TG665

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