稀土Y及CNTs在ADC12中的应用及性能分析

发布时间：2018-03-10 15:42

本文选题：ADC12铝合金　切入点：稀土Y　出处：《南昌大学》2017年硕士论文　论文类型：学位论文

【摘要】：ADC12铝合金属于Al-Si-Cu系合金,具有较高的比强度,较小的热膨胀系数,较好的耐腐蚀性以及优良的导电导热性能。该合金的铸造性能优良,但铸造组织中的α-Al枝晶粗大,共晶硅相呈粗大板片状,β-Fe相呈粗大长针状,这均会导致其力学性能降低,极大限制了ADC12铝合金的应用。本文主要研究了稀土Y及CNTs在ADC12铝合金中的应用及性能。研究结果表明:稀土Y可以显著细化ADC12铝合金中的α-Al相并改善共晶硅相的形貌。当稀土Y的含量为0.2wt%时,α-Al相得到了较佳的细化效果,合金的二次枝晶臂间距(6.9μm)最低,较未变质合金下降了75.6%。共晶硅相转变为细小的纤维状或颗粒状而且尖角消失,平均面积降至1.7μm2,长径比降至1.9,较未变质合金分别降低了96.1%和89.0%,这表明共晶硅相得到了完全变质。β-Fe相为细小的短杆状,其长度为3.1μm,比未变质合金分降低了85.8%。合金的极限抗拉强度、延伸率和硬度分别达到了255.62MPa、3.25%和94.6HV,较未变质ADC12铝合金分别提高了48.3%、72.9%和24.6%。然而当稀土Y的含量进一步提高到0.3wt%时,合金的α-Al相,共晶硅相及β-Fe相均开始粗化。对于稀土Y变质ADC12铝合金,较适宜的固溶温度为520°C。固溶处理后,共晶硅相得到较好的球化效果,同时β-Fe相尺寸减小且尖角变钝,这有均利于合金的力学性能。当固溶温度为500°C,虽然共晶硅相得到了较好的球化效果,但短杆状的β-Fe相的尺寸较大且尖角未消失。当固溶温度为540°C时,合金出现了明显的过烧现象,部分共晶硅相及富铁相显著粗化,另一部分共晶硅相及富铁相呈雨点状与富铜相密集的分布在合金晶界处。在ADC12铝合金中加入稀土Y后,固溶组织中的共晶硅相尺寸得到了细化且尺寸更均匀,富铁相也得到了较好的细化,Al2Cu相的溶解更完全。0.2wt%稀土Y变质ADC12铝合金在520°C下固溶8h,然后经过淬火以及170°C下时效10h后,合金的抗拉强度(313.51MPa)、延伸率(3.19%)和硬度(132.7HV)较未热处理ADC12基体分别提高了81.89%、70.59%和74.31%。高能超声法较机械搅拌法的分散能力更强。高能超声法制备CNTs/ADC12合金中,CNTs的添加能够改善共晶硅相的形貌,由粗大的长针状转变为颗粒状。当碳纳米管含量为1.0wt%时,其极限抗拉强度(251.91MPa)和硬度(103.34HV)均达到最大值,较ADC12基体分别提高了27.0%和29.5%。当CNTs含量为1.5wt%时,碳纳米管开始团聚。通过分析合金的拉伸断口发现,高能超声法较机械搅拌法对碳纳米管分散效果更好。通过TEM分析合金的界面发现,高能超声法能够抑制碳纳米管与铝合金基体之间反应生成Al4C3相,同时能够提高碳纳米管与铝合金基体之间的润湿性。
[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 伪 -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 伪 -Al phase in ADC12 aluminum alloy and improve eutectic silicon phase. Morphology. When the content of rare earth Y is 0.2 wt%, 伪 -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 伪 -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 掳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 掳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 掳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 掳C for 8 h, then quenched and aged at 170 掳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.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21

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