發(fā)布時(shí)間：2018-03-05 23:17

  本文選題：超聲　切入點(diǎn)：原位　出處：《南昌大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：鋁合金具有密度小、比強(qiáng)度高、成形性好、易于回收利用等優(yōu)點(diǎn),因而在國民經(jīng)濟(jì)中得到了較為廣泛的應(yīng)用。作為一種Al-Si-Cu系合金,ADC12因其優(yōu)越的性能而被廣泛應(yīng)用于汽車工業(yè)領(lǐng)域。但是,合金組織中粗大的α-Al相和Si相卻在一定程度上降低了材料的力學(xué)性能。而研究發(fā)現(xiàn),一些原位增強(qiáng)相(如Al2O3、Al3Ti顆粒等)能夠改善Al-Si合金組織,提高材料的各方面性能。故本文以Al-B2O3、Al-K2Ti F6、Al-Ti為反應(yīng)體系,將高能超聲處理技術(shù)與原位合成技術(shù)相結(jié)合,制備了原位(Al2O3、Al3Ti)顆粒增強(qiáng)ADC12鋁基復(fù)合材料,力求利用超聲產(chǎn)生的聲空化效應(yīng)和聲流效應(yīng)來細(xì)化顆粒,改善顆粒與熔體間的潤濕性,迫使顆粒在熔體中均勻分散,從而提高復(fù)合材料的綜合性能,使其能夠更好的符合鋁基復(fù)合材料的要求。另外,本文在以Al-K2TiF6為反應(yīng)體系制備Al3Ti/ADC12復(fù)合材料的同時(shí),還研究了電磁攪拌對其半固態(tài)漿料組織的影響,力求利用電磁攪拌作用于熔體時(shí)產(chǎn)生的強(qiáng)烈混合對流來改善晶體的結(jié)晶凝固過程,從而獲得良好的復(fù)合材料半固態(tài)漿料。主要研究內(nèi)容及結(jié)果如下:以Al-B2O3為反應(yīng)體系,原位制備了Al2O3/ADC12復(fù)合材料。復(fù)合材料的微觀組織研究表明:超聲輔助下原位生成的Al2O3增強(qiáng)顆粒細(xì)小、圓整,在基體中分布也較為均勻;復(fù)合材料硅相組織與基體相比有了一定程度的改善,硅相形貌由原來的塊狀、長針狀、板條狀逐步轉(zhuǎn)變?yōu)槎贪魻�、顆粒狀,其中未施加超聲制備的復(fù)合材料組織中的硅相以短棒狀為主,顆粒狀較少,超聲后復(fù)合材料組織中的短棒狀硅相減少、且尺寸變得更為細(xì)小,顆粒狀硅相則有所增加。復(fù)合材料的力學(xué)性能研究表明:經(jīng)過超聲處理的復(fù)合材料抗拉強(qiáng)度和延伸率比未施加超聲的復(fù)合材料分別提高了13.5%和25.2%。以Al-K2TiF6為反應(yīng)體系,采用熔體直接反應(yīng)法,超聲原位合成了Al3Ti/ADC12復(fù)合材料。研究表明:與常規(guī)原位反應(yīng)相比,超聲作用下反應(yīng)更快、更徹底,且生成的Al3Ti增強(qiáng)顆粒形貌較規(guī)則、尺寸細(xì)小,平均尺寸約為1~2μm,在基體中分布也較為均勻。原位復(fù)合材料的鑄態(tài)組織與基體相比均有所改善:α-Al相的輪廓變得愈加清晰,尺寸逐漸細(xì)化,形貌趨于圓整;Si相形貌則由原來的長針狀、板條狀逐步轉(zhuǎn)變?yōu)槎贪魻�、顆粒狀。其中未施加超聲制備的復(fù)合材料晶粒得到了一定的細(xì)化,Si相形貌以較大顆粒狀為主,短棒狀較少;二次超聲條件下獲得的復(fù)合材料晶粒得到了較大程度的細(xì)化,Si相形貌則變?yōu)榱烁蛹?xì)小的顆粒狀甚至纖維狀。而經(jīng)過超聲處理的復(fù)合材料抗拉強(qiáng)度和伸長率分別達(dá)到255.2MPa和2.18%,比未施加超聲的復(fù)合材料分別提高了19.4%和33.7%。復(fù)合材料的室溫拉伸斷口形貌分析表明:在超聲作用下,復(fù)合材料斷口上解理面變少,韌窩變小、變深、數(shù)量增多,表現(xiàn)為明顯的韌性斷裂。以Al-K2TiF6為反應(yīng)體系,采用電磁攪拌法成功制備了原位Al3Ti/ADC12復(fù)合材料的半固態(tài)漿料,并研究了不同攪拌參數(shù)對該復(fù)合材料半固態(tài)組織的影響,揭示了半固態(tài)組織在電磁場作用下的演變機(jī)理。結(jié)果表明:在本實(shí)驗(yàn)降溫?cái)嚢柽^程中,隨著攪拌時(shí)間的逐漸增加,復(fù)合材料半固態(tài)組織中的初生相形貌發(fā)生了多樣性變化,經(jīng)歷了樹枝狀、薔薇狀、近球狀的演變,其中在585℃時(shí)水淬取樣的組織較佳,初生α-Al相主要呈近球狀,彌散懸浮于液相中,平均尺寸約為35.2μm;在一定范圍內(nèi),若固定相同的攪拌頻率和攪拌時(shí)間,降溫?cái)嚢柽^程中隨著攪拌電壓的增大晶粒形貌趨于圓整,尺寸逐漸變小;若固定相同的攪拌電壓和攪拌時(shí)間,降溫?cái)嚢柽^程中隨著攪拌頻率的增大晶粒先逐漸細(xì)化而后又逐漸增大。以Al-Ti為反應(yīng)體系原位合成了Al3Ti/ADC12鋁基復(fù)合材料。研究表明:對熔體施加機(jī)械攪拌后,復(fù)合材料組織中的Al3Ti顆粒相由原來的粘結(jié)、團(tuán)聚慢慢變得分散開來,平均尺寸也有所減小;冷卻方式的不同對復(fù)合材料中原位Al3Ti相的形貌也有較大的影響,在快速冷卻的條件下,Al3Ti相的形貌為塊狀或顆粒狀,而經(jīng)緩慢冷卻后,Al3Ti相的形貌卻變?yōu)獒槧罨虬鍡l狀。對熔體施加超聲后,復(fù)合材料組織中的Al3Ti相發(fā)生了較大的變化:若保持超聲時(shí)間、超聲頻率及Ti的添加量不變,在一定范圍內(nèi),隨著超聲功率的增加,Al3Ti顆粒尺寸變得越來越細(xì)小,分布也變得更加均勻;若保持超聲功率、超聲時(shí)間及超聲頻率不變,隨著Ti含量的逐漸增加,Al3Ti顆粒會(huì)出現(xiàn)團(tuán)聚和長大的現(xiàn)象;若保持超聲功率、超聲頻率不變,隨著超聲時(shí)間的增加,超聲效果會(huì)出現(xiàn)先加強(qiáng)后減弱的趨勢。此外,原位Al3Ti/ADC12鋁基復(fù)合材料的抗拉強(qiáng)度較基體合金而言有升高的趨勢,并且復(fù)合材料的力學(xué)性能變化趨勢與其組織變化趨勢相一致,當(dāng)Ti添加量為3%、超聲功率為1.5kw、頻率為20kHz、超聲時(shí)間為6min時(shí),其綜合力學(xué)性能較好,抗拉強(qiáng)度為247.34MPa、延伸率為2.31%,比未施加超聲的復(fù)合材料分別提高了21.3%和50.0%。而且,Ti的加入還能夠細(xì)化基體組織中的α-Al相,使其由原來的粗大樹枝狀逐漸轉(zhuǎn)變?yōu)榧?xì)小枝晶狀、薔薇狀甚至近球狀。
[Abstract]:Aluminum Alloy has the advantages of low density, high specific strength, good formability, easy recycling and other advantages, so it has been widely used in the national economy. As a kind of Al-Si-Cu alloy, ADC12 because of its superior performance and is widely used in the field of automotive industry. However, the thick alloy of alpha -Al and the Si phase was reduced to a certain extent the mechanical properties of the materials. The study found that some in situ Reinforcement (such as Al2O3, Al3Ti particles) can improve the microstructure of Al-Si alloy, improve the properties of materials. This paper uses Al-B2O3, Al-K2Ti F6, Al-Ti reaction system, the high-energy ultrasound technique and in situ synthesis combined in situ preparation of (Al2O3, Al3Ti) ADC12 particles reinforced aluminum matrix composites, and strive to produce cavitation effect of the ultrasonic flow effect to fine particles, improve the wettability between particles and melt, forcing the particles Uniformly dispersed in the melt, thereby improving the performance of the composite materials, so that it can better meet the requirements of aluminum matrix composites. In addition, at the same time this system as the reaction system in Al-K2TiF6 Al3Ti/ADC12 composites, also studied the effect of electromagnetic stirring on the microstructure of the semi-solid slurry, stirring to strong mixed convection on the melt produced by electromagnetic crystal to improve the solidification process, so as to obtain good composite semi solid slurry. The main research contents and results are as follows: in the Al-B2O3 reaction system, Al2O3/ADC12 composite material was synthesized. The microstructure of the composites showed that the ultrasonic assisted Al2O3 in situ reinforced fine particles, round, distribution is more uniform in the matrix; composite silicon phase structure compared with the matrix has been improved to some extent, the Si morphology from the original block Long needle, lath, gradually transformed into short rod like particles, which does not apply, the microstructure of the composite ultrasonic preparation of silicon phase in the short rod, granular small, short rod shaped silicon composite tissue after ultrasound in phase decreased, and the size become smaller, granular silicon phase increased. Study on the mechanical properties of the composites show that the composite tensile strength and elongation of ultrasonic treatment than the composite without ultrasonic respectively increased by 13.5% and 25.2%. by Al-K2TiF6 reaction system, using the direct melt reaction method, ultrasonic in-situ Al3Ti/ADC12 composites were synthesized. The results show that: compared with conventional in situ reaction, the effects of ultrasound the reaction faster and more thoroughly, and the Al3Ti particles morphology was regular, the size is small, the average size is about 1~2 m, the distribution is more uniform in the matrix. The cast in situ composite materials Compared with the matrix organization are improved: a -Al phase profile becomes more and more clear, size gradually thinning, morphology tended to be round; Si morphology from long acicular lath gradually transformed into short rod, which is not applied. Granular material grain ultrasonic prepared to be refined, Si the morphology in large granular, short rod less; composite grains obtained two times under ultrasonic condition was refined obviously, the morphology of Si phase is changed to fine granular fibrous. Even after ultrasonic treatment of the composite tensile strength and elongation are 255.2MPa and 2.18% respectively, compared with the composite without applying ultrasound respectively improved 19.4% and the tensile fracture morphology of 33.7%. composite analysis shows that under the action of ultrasound, fracture of composite materials on the cleavage surface becomes less, dimple becomes small, dark, increase in the number of ,琛ㄧ幇涓烘槑鏄劇殑闊ф，

本文編號(hào)：1572323