本文選題：ADC12鋁合金　切入點(diǎn)：稀土Y　出處：《南昌大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：ADC12鋁合金屬于Al-Si-Cu系合金,具有較高的比強(qiáng)度,較小的熱膨脹系數(shù),較好的耐腐蝕性以及優(yōu)良的導(dǎo)電導(dǎo)熱性能。該合金的鑄造性能優(yōu)良,但鑄造組織中的α-Al枝晶粗大,共晶硅相呈粗大板片狀,β-Fe相呈粗大長針狀,這均會(huì)導(dǎo)致其力學(xué)性能降低,極大限制了ADC12鋁合金的應(yīng)用。本文主要研究了稀土Y及CNTs在ADC12鋁合金中的應(yīng)用及性能。研究結(jié)果表明:稀土Y可以顯著細(xì)化ADC12鋁合金中的α-Al相并改善共晶硅相的形貌。當(dāng)稀土Y的含量為0.2wt%時(shí),α-Al相得到了較佳的細(xì)化效果,合金的二次枝晶臂間距(6.9μm)最低,較未變質(zhì)合金下降了75.6%。共晶硅相轉(zhuǎn)變?yōu)榧?xì)小的纖維狀或顆粒狀而且尖角消失,平均面積降至1.7μm2,長徑比降至1.9,較未變質(zhì)合金分別降低了96.1%和89.0%,這表明共晶硅相得到了完全變質(zhì)。β-Fe相為細(xì)小的短桿狀,其長度為3.1μm,比未變質(zhì)合金分降低了85.8%。合金的極限抗拉強(qiáng)度、延伸率和硬度分別達(dá)到了255.62MPa、3.25%和94.6HV,較未變質(zhì)ADC12鋁合金分別提高了48.3%、72.9%和24.6%。然而當(dāng)稀土Y的含量進(jìn)一步提高到0.3wt%時(shí),合金的α-Al相,共晶硅相及β-Fe相均開始粗化。對(duì)于稀土Y變質(zhì)ADC12鋁合金,較適宜的固溶溫度為520°C。固溶處理后,共晶硅相得到較好的球化效果,同時(shí)β-Fe相尺寸減小且尖角變鈍,這有均利于合金的力學(xué)性能。當(dāng)固溶溫度為500°C,雖然共晶硅相得到了較好的球化效果,但短桿狀的β-Fe相的尺寸較大且尖角未消失。當(dāng)固溶溫度為540°C時(shí),合金出現(xiàn)了明顯的過燒現(xiàn)象,部分共晶硅相及富鐵相顯著粗化,另一部分共晶硅相及富鐵相呈雨點(diǎn)狀與富銅相密集的分布在合金晶界處。在ADC12鋁合金中加入稀土Y后,固溶組織中的共晶硅相尺寸得到了細(xì)化且尺寸更均勻,富鐵相也得到了較好的細(xì)化,Al2Cu相的溶解更完全。0.2wt%稀土Y變質(zhì)ADC12鋁合金在520°C下固溶8h,然后經(jīng)過淬火以及170°C下時(shí)效10h后,合金的抗拉強(qiáng)度(313.51MPa)、延伸率(3.19%)和硬度(132.7HV)較未熱處理ADC12基體分別提高了81.89%、70.59%和74.31%。高能超聲法較機(jī)械攪拌法的分散能力更強(qiáng)。高能超聲法制備CNTs/ADC12合金中,CNTs的添加能夠改善共晶硅相的形貌,由粗大的長針狀轉(zhuǎn)變?yōu)轭w粒狀。當(dāng)碳納米管含量為1.0wt%時(shí),其極限抗拉強(qiáng)度(251.91MPa)和硬度(103.34HV)均達(dá)到最大值,較ADC12基體分別提高了27.0%和29.5%。當(dāng)CNTs含量為1.5wt%時(shí),碳納米管開始團(tuán)聚。通過分析合金的拉伸斷口發(fā)現(xiàn),高能超聲法較機(jī)械攪拌法對(duì)碳納米管分散效果更好。通過TEM分析合金的界面發(fā)現(xiàn),高能超聲法能夠抑制碳納米管與鋁合金基體之間反應(yīng)生成Al4C3相,同時(shí)能夠提高碳納米管與鋁合金基體之間的潤濕性。
[Abstract]:ADC12 aluminum alloy belongs to Al-Si-Cu series alloy, which has higher specific strength, smaller coefficient of thermal expansion, better corrosion resistance and excellent conductivity and thermal conductivity. The casting property of the alloy is excellent, but the 偽 -Al dendrite in casting structure is coarse. The mechanical properties of eutectic silicon phase and 尾 -Fe phase are reduced. The application and properties of rare earth Y and CNTs in ADC12 aluminum alloy are studied in this paper. The results show that rare earth Y can refine 偽 -Al phase in ADC12 aluminum alloy and improve eutectic silicon phase. Morphology. When the content of rare earth Y is 0.2 wt%, 偽 -Al phase has a better refinement effect. The secondary dendritic arm spacing (6.9 渭 m) of the alloy is the lowest, which is 75.6% lower than that of the unmodified alloy. The eutectic silicon phase is transformed into fine fibrous or granular, and the sharp angle disappears. The average area is reduced to 1.7 渭 m ~ 2 and the aspect ratio to 1.9, which is 96.1% and 89.0 lower than that of the unmodified alloy, respectively. It shows that the eutectic silicon phase is completely modified. The 尾 -Fe phase is a small short rod with a length of 3.1 渭 m, which is 85.8% lower than that of the unmodified alloy, and the ultimate tensile strength of the alloy is 85.8% lower than that of the unmodified alloy. The elongation and hardness of the alloy reached 255.62 MPA 3.25% and 94.6 HVrespectively, which increased 48.3% and 24.6% compared with the unmodified ADC12 aluminum alloy, respectively. However, when the content of rare earth Y was further increased to 0.3 wt%, the 偽 -Al phase of the alloy was increased. The eutectic silicon phase and 尾 -Fe phase begin to coarsening. For rare earth Y modified ADC12 aluminum alloy, the suitable solution temperature is 520 擄C. after solution treatment, eutectic silicon phase has better spheroidization effect, and 尾 -Fe phase size decreases and the sharp angle becomes obtuse. When the solution temperature is 500 擄C, the eutectic silicon phase has a better spheroidizing effect, but the 尾 -Fe phase with short rod shape is larger in size and does not lose its sharp angle, when the solution temperature is 540 擄C. The alloy appears obvious overburning phenomenon, some eutectic silicon phase and iron rich phase are coarsened obviously, the other part of eutectic silicon phase and iron rich phase distribute densely at the grain boundary of the alloy in the form of raindrops and copper-rich phase. After adding rare earth Y to ADC12 aluminum alloy, The size of eutectic silicon phase in the solution structure was refined and the size was more uniform, and the iron phase was finely refined. The dissolution of Al _ 2Cu phase was more complete. 0.2 wt% rare earth Y modified ADC12 aluminum alloy was dissolved at 520 擄C for 8 h, then quenched and aged at 170 擄C for 10 h. The tensile strength of the alloy was 313.51MPa1, elongation was 3.19) and hardness 132.7HV) increased by 81.89% and 74.31% than that of the untreated ADC12 matrix, respectively. The dispersion ability of the high-energy ultrasonic method was better than that of the mechanical stirring method. The addition of the high-energy ultrasonic method to the preparation of CNTs/ADC12 alloy could be improved. Morphology of eutectic silicon phase, The maximum tensile strength (251.91MPa) and hardness (103.34HVV) were obtained when the content of carbon nanotubes was 1.0 wt%, which was 27.0% and 29.5wt% higher than that of ADC12 matrix, respectively. When the content of CNTs was 1.5 wt%, the maximum values were obtained. By analyzing the tensile fracture of the alloy, it was found that the high energy ultrasonic method was better than the mechanical stirring method in dispersing the carbon nanotubes. The TEM analysis of the interface of the alloy revealed that the high energy ultrasonic method was more effective than the mechanical stirring method in dispersing the carbon nanotubes. High energy ultrasonic method can inhibit the reaction between carbon nanotubes and aluminum alloy matrix to form Al4C3 phase and improve the wettability between carbon nanotubes and aluminum alloy matrix.
【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】：2017
【分類號(hào)】：TG146.21

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