本文選題：Al-Si合金 + 稀土Sm��； 參考：《南昌大學(xué)》2015年碩士論文

【摘要】：Al-Si系鑄造合金是一種傳統(tǒng)的工業(yè)用鋁合金材料,因其原料成本低廉且具有良好的鑄造、焊接及耐磨性能而廣泛應(yīng)用。ZL101和ZL102合金為兩種典型的Al-Si系鑄造合金。然而,其鑄態(tài)顯微組織特性為多邊形塊狀的初晶硅和粗大針狀的共晶硅,α-Al枝晶粗大,導(dǎo)致合金的力學(xué)性能惡化。本文主要對(duì)稀土釤(Sm)及碳納米管(CNTs)在鋁硅合金中的應(yīng)用及性能進(jìn)行研究。研究結(jié)果表明:稀土Sm能降低Al-Si合金的共晶溫度。加入量越多,則降低幅度越大。當(dāng)加入0.6wt.%Sm時(shí),共晶溫度最低。共晶溫度低是具有良好變質(zhì)組織合金的一個(gè)共同的特征。對(duì)顯微組織而言:ZL101的α-Al二次枝晶臂間距隨著Sm含量增加而減少,當(dāng)Sm的含量達(dá)0.6wt.%時(shí),二次枝晶臂間距值最低,由原來的40μm變?yōu)?7μm;而此時(shí)ZL102合金的α-Al呈雙重枝晶-晶胞結(jié)構(gòu)和松樹結(jié)構(gòu)分布,枝晶數(shù)量增多。Sm對(duì)Al-Si合金的共晶硅相變質(zhì)能力較強(qiáng)�？蓪l-Si系合金中細(xì)長針狀變質(zhì)為細(xì)小圓整的顆粒狀。對(duì)于ZL102合金,添加適量稀土Sm能同時(shí)變質(zhì)初晶硅和共晶硅。此外,稀土Sm能提高Al-Si系合金的力學(xué)性能。當(dāng)0.6wt.%Sm加入時(shí),合金具有良好的綜合力學(xué)性能。CNTs的韌性和結(jié)構(gòu)穩(wěn)定性良好,作為增強(qiáng)相加入合金后,復(fù)合材料的性能將帶來一次飛躍。然而CNTs密度低,尺寸小,比表面積大,難以分散,與鋁合金基體潤濕性差。因此,為了解決上述問題,本課題首先制備了CNTs含量高的Al-CNTs中間納米復(fù)合材料作為CNTs的載體,然后加入鋁硅合金熔體稀釋輔以施加機(jī)械攪拌或超聲制備CNTs/ZL101復(fù)合材料。在Al-CNTs中間納米復(fù)合材料中,CNTs含量越多,熔化時(shí)間越長,CNTs的最佳含量為5~8wt.%。Al-CNTs中間納米復(fù)合材料經(jīng)熱擠壓后可縮短其熔化時(shí)間。采用機(jī)械攪拌法制備的CNTs/ZL101復(fù)合材料,隨著CNTs的加入,顯微組織得到細(xì)化。但是由于機(jī)械攪拌法對(duì)CNTs的分散能力有限,當(dāng)CNTs含量超過0.4wt.%時(shí),復(fù)合材料的內(nèi)部缺陷多,存在大量的CNTs團(tuán)聚物,導(dǎo)致復(fù)合材料力學(xué)性能下降。當(dāng)CNTs含量為0.2wt.%時(shí),復(fù)合材料的顯微硬度及力學(xué)性能最佳,與基體相比,硬度和極限抗拉強(qiáng)度分別提高了36.8%、18.8%。采用超聲法制備的CNTs/ZL101復(fù)合材料與機(jī)械攪拌法相比,CNTs的團(tuán)聚物在超聲的空化效應(yīng)作用下在復(fù)合材料內(nèi)均勻分布,共晶硅及α-Al也得到細(xì)化。超聲功率越大,復(fù)合材料的顯微組織越好,最佳的超聲功率為2.1kw。在功率2.1kw超聲作用下,0.8wt.%CNTs/ZL101復(fù)合材料的硬度、極限抗拉強(qiáng)度和延伸率最高,最低功率(0.7kw)相比,分別提高了22.8%、17.8%和47.2%。另外,隨著CNTs含量的增加,復(fù)合材料的硬度和抗拉強(qiáng)度不斷上升,當(dāng)CNTs加入量達(dá)1.2wt.%時(shí)最高,分別為HV106.3、267MPa,與基體相比,提高了36.1%、19.7%。
[Abstract]:Al-Si series casting alloy is a kind of traditional industrial aluminum alloy. Because of its low raw material cost and good casting, welding and wear resistance, it is widely used. ZL101 and ZL102 alloy are two typical Al-Si casting alloys. However, the as-cast microstructures are polygonal bulk primary silicon and coarse acicular eutectic silicon, and 偽 -Al dendrite is coarse, which results in the deterioration of mechanical properties of the alloy. In this paper, the application and properties of rare earth samarium and carbon nanotube (CNTs) in Al-Si alloy were studied. The results show that rare earth Sm can reduce the eutectic temperature of Al-Si alloy. The greater the addition, the greater the reduction. The eutectic temperature is the lowest when 0.6wt.%Sm is added. Low eutectic temperature is a common feature of good modified alloys. For microstructures, 偽 -Al secondary dendritic arm spacing decreases with the increase of Sm content. When Sm content reaches 0.6 wt.%, the secondary dendritic arm spacing is the lowest. At the same time, 偽 -Al of ZL102 alloy was distributed as double dendritic cell structure and pine tree structure, and the ability of eutectic silicon phase modification of Al-Si alloy was stronger when the number of dendrite increased. The fine needle shape of Al-Si alloy can be modified into fine round granular. For ZL102 alloy, the addition of appropriate amount of rare earth Sm can modify both primary silicon and eutectic silicon at the same time. In addition, rare earth Sm can improve the mechanical properties of Al-Si alloys. When 0.6wt.%Sm was added, the alloy had good comprehensive mechanical properties. The toughness and structural stability of the alloy were good, and the properties of the composites would take a leap forward when the alloy was added as a reinforcing phase. However, CNTs has low density, small size, large specific surface area, difficult to disperse, and poor wettability with aluminum alloy matrix. Therefore, in order to solve the above problems, the Al-CNTs intermediate nanocomposites with high CNTs content were prepared as the carrier of CNTs, and then the CNTs/ZL101 composites were prepared by adding melt dilution of Al-Si alloy and adding mechanical stirring or ultrasonic. The more the content of Al-CNTs is, the longer the melting time is, and the best content is that the melting time of 5~8wt.%.Al-CNTs intermediate nanocomposites can be shortened after hot extrusion. The microstructure of CNTs/ZL101 composites prepared by mechanical stirring method was refined with the addition of CNTs. However, due to the limited dispersion of CNTs by mechanical stirring method, when the content of CNTs exceeds 0.4 wt.%, the internal defects of the composites are more and a large number of CNTs aggregates exist, which leads to the decline of mechanical properties of the composites. When the content of CNTs is 0.2 wt.%, the microhardness and mechanical properties of the composites are the best. Compared with the matrix, the hardness and ultimate tensile strength of the composites are increased by 36.8% and 18.8%, respectively. Compared with the mechanical stirring method, the aggregates of CNTs/ZL101 prepared by ultrasonic method are uniformly distributed in the composites under the effect of ultrasonic cavitation, and the eutectic silicon and 偽 -Al are also refined. The higher the ultrasonic power, the better the microstructure of the composite, and the optimum ultrasonic power is 2.1 kw. The hardness, ultimate tensile strength and elongation of CNTs / ZL101 composites were increased by 22.8wt% and 47.2%, respectively. In addition, the hardness and tensile strength of the composites increased with the increase of CNTs content. When the content of CNTs reached 1.2wt.%, the highest content was HV106.3267MPa. compared with the matrix, the hardness and tensile strength of the composites were increased by 36.1% and 19.79.7MPa.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG146.21

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本文編號(hào)：1836233