發(fā)布時(shí)間：2018-08-17 16:46

【摘要】：本課題采用先進(jìn)的選區(qū)激光熔化(Selective Laser Melting,SLM)工藝成形球磨均勻的Al_2O_3/Al和Al_2O_3/AlSi_(10)Mg混合粉末,從而成功制備了Al_2O_3/Al以及原位Al_2Si_4O_(10)/Al復(fù)合材料試樣。研究了陶瓷顆粒增強(qiáng)Al基復(fù)合材料的SLM成形工藝,探討了SLM工藝參數(shù)對(duì)AMCs試樣物相、致密度、顯微組織、硬度及摩擦磨損性能的影響。進(jìn)而優(yōu)化工藝參數(shù),獲得最佳性能的材料。在以上基礎(chǔ)上,進(jìn)一步調(diào)研了擇優(yōu)化參數(shù)下成形的Al_2Si_4O_(10)/Al復(fù)合材料試樣的摩擦磨損性能。得出以下主要結(jié)論:針對(duì)Al_2O_3/Al復(fù)合材料的SLM成形,當(dāng)激光線能量密度(η)較低時(shí),SLM成形的Al_2O_3/Al試樣冶金缺陷較多,致密度較低,斷裂不連續(xù)的Al_2O_3增強(qiáng)相發(fā)生嚴(yán)重團(tuán)聚現(xiàn)象,且與Al基體界面結(jié)合較弱,成形試樣硬度及耐磨性較差。合理地增加η至236 J/m,試樣表面光滑、致密,無(wú)明顯冶金缺陷,長(zhǎng)條狀A(yù)l_2O_3增強(qiáng)相顯著細(xì)化,分布均勻,且與Al基體具有良好的界面結(jié)合。此時(shí)成形試樣性能優(yōu)異,平均顯微硬度值高達(dá)175 HV0.1,摩擦系數(shù)和磨損率分別低至0.33和9.78×10-5 mm3 N-1 m-1。針對(duì)原位Al_2Si_4O_(10)/Al復(fù)合材料的SLM成形,當(dāng)η較低時(shí),Al_2Si_4O_(10)增強(qiáng)相之間結(jié)合性較差,并呈現(xiàn)不均勻的分布,而當(dāng)η較高為350 J/m時(shí),晶粒發(fā)生嚴(yán)重粗化,以上都降低了成形試樣的性能。擇優(yōu)化η為289 J/m時(shí),在激光核心區(qū),Al基體以胞狀枝晶形態(tài)生長(zhǎng),環(huán)狀A(yù)l_2Si_4O_(10)增強(qiáng)相之間結(jié)合良好,分散均勻,同時(shí)其晶粒顯著細(xì)化。在激光重熔區(qū)內(nèi),Al基體呈現(xiàn)柱狀枝晶形貌,環(huán)狀A(yù)l_2Si_4O_(10)增強(qiáng)相略微粗化,同時(shí)Al基體上分散著大量細(xì)小的Al_2Si_4O_(10)增強(qiáng)顆粒,此時(shí)成形試樣的納米硬度和摩擦磨損特性得到顯著提高。針對(duì)原位Al_2Si_4O_(10)/Al復(fù)合材料的摩擦磨損實(shí)驗(yàn),載荷的增加使試樣表面顆粒破損程度增大,進(jìn)而導(dǎo)致了嚴(yán)重的三體磨粒磨損,加劇了試樣表面的磨損�；�移速度越大,摩擦熱效應(yīng)及熱量聚集越明顯,表面溫升越高,從而促進(jìn)了硬質(zhì)Al_2O_3的生成及Fe_2O_3的轉(zhuǎn)移,提高了AMCs試樣的摩擦磨損特性。長(zhǎng)時(shí)間摩擦磨損中,摩擦系數(shù)值在0.65和0.55之間波動(dòng)。磨損后期,摩擦熱量發(fā)生積累,導(dǎo)致試樣表面硬質(zhì)Al_2O_3反應(yīng)物和Fe_2O_3轉(zhuǎn)移層的數(shù)量大大增加,因此降低了摩擦系數(shù)的波動(dòng)程度。
[Abstract]:In this paper, the advanced selective laser melting (Selective Laser Meltings-SLM process was used to fabricate the Al_2O_3/Al and Als _ 2O _ 3 / AlSi _ (10) mg mixed powders, and the Al_2O_3/Al and Al _ 2SiS _ 4O _ (10) / Al composite samples were successfully prepared. The SLM forming process of ceramic particle reinforced Al matrix composites was studied. The effects of SLM process parameters on the phase, density, microstructure, hardness and friction and wear properties of AMCs samples were investigated. Then the process parameters are optimized and the material with the best performance is obtained. On the basis of the above, the friction and wear properties of Al _ 2Si _ 4O _ (10) / Al composite specimens formed under optimized parameters were investigated. The main conclusions are as follows: for the SLM forming of Al_2O_3/Al composites, when the laser energy density (畏) is low, there are more metallurgical defects, lower density and serious agglomeration of the Al_2O_3 reinforced phase with discontinuous fracture. The interface with Al matrix is weak and the hardness and wear resistance of the formed samples are poor. By increasing 畏 to 236J / m reasonably, the surface of the sample is smooth and compact, and there is no obvious metallurgical defect. The long strip Al_2O_3 reinforced phase is finer, more evenly distributed, and has a good interface with Al matrix. The average microhardness is 175HV0.1, and the friction coefficient and wear rate are as low as 0.33 and 9.78 脳 10 ~ (-5) mm3 N-1 ~ (-1) m ~ (-1), respectively. For the SLM forming of in situ Al2Si4O10 / Al composites, when 畏 is lower, the adhesion between Al2Si4O10 / Al2Si4O10 reinforcements is poor, and the distribution is uneven. When 畏 is higher than 350J / m, the grain size coarsens seriously, which reduces the properties of the formed specimens. When the optimized 畏 is 289 J / m, the Al matrix in the laser core region grows in cellular dendritic morphology, and the circular Al2Si4O10 reinforcement phase is well bonded and uniformly dispersed, and the grain size is significantly refined. In the laser remelting zone, the Al matrix presents a columnar dendritic morphology, the annular Al2Si4O10 reinforcement phase is slightly coarser, and a large number of fine AlStack-Si4O10 reinforced particles are dispersed on the Al matrix. The nano-hardness and friction and wear properties of the formed samples are greatly improved. According to the friction and wear experiments of Al _ 2Si _ 4O _ (10) / Al composites in situ, the wear degree of the surface particles increased with the increase of load, which led to serious wear of three-body abrasive particles and aggravated the wear of the specimen surface. The higher the slip rate, the more obvious the friction heat effect and heat accumulation, the higher the surface temperature rise, thus the formation of hard Al_2O_3 and the transfer of Fe_2O_3 are promoted, and the friction and wear characteristics of AMCs samples are improved. The friction coefficient fluctuates between 0.65 and 0.55 during long time friction and wear. At the later stage of wear, the friction heat accumulates, which results in a great increase in the number of hard Al_2O_3 reactants and Fe_2O_3 transfer layers on the surface of the specimen, thus reducing the fluctuation degree of friction coefficient.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB333

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