两种工程用铝合金的强化技术研究

发布时间：2018-04-27 22:25

本文选题：Al-Si合金 + Al-Mn合金　；参考：《济南大学》2016年硕士论文

【摘要】：铝合金在工业上的大范围使用虽然较晚,但已发展成为除钢铁外的第二大金属材料,其发展速度可见一斑。在汽车的轻量化方面,铝合金的应用起着很大作用,利用铸造铝合金代替原有的钢铁材料,不仅可以减轻汽车的总体质量,还可以节省能耗,减少污染。在变形铝合金方面,铝板、铝带、铝管等铝材料也广泛应用在建筑、包装、机械等方面。目前,由于铝合金的强度较低,严重限制了其发展,因此,开发出新成分、新工艺的高强度铝合金已成为目前研究的重中之重。本论文一部分以铸造Al-Si合金为对象,研究可提高其强度的强化手段;另一部分依据“高性能铝单板材料的研制”项目,研究可提高Al-Mn合金强度,并保持其良好塑性的强化手段。本文利用拉伸试验、金相显微镜、偏光显微镜、扫描电镜及能谱分析、X射线衍射、电化学腐蚀、热分析等手段来研究合金化、细化变质、热速处理以及熔体复合处理对Al-Si及Al-Mn合金的影响。确定Al-Si合金基体成分为:Al-9Si-0.5Mg。利用差示扫描量热分析(DSC),发现合金在855~885℃范围出现熔体结构转变。根据此温度范围确定Al-9Si-0.5Mg合金的热速处理温度为830℃~990℃。实验结果表明,随着热速处理时熔体温度的改变,合金的力学性能及微观组织也发生改变。当合金熔体温度达到930℃并保温20min后,加入冷料时熔体温度快速降到浇注温度(760℃)并保温10min时,合金的力学性能达到最好,它的抗拉强度、屈服强度、硬度以及伸长率与常规熔炼工艺下相比分别提高了24.3%、37.7%、82.9%、21.8%。合金的中α-Al晶粒由粗大的枝晶转变为柱状或等轴状晶粒,共晶Si则由长针状转变为颗粒状,可见热速处理可使合金的微观组织得到明显细化。在Al-9Si-0.5Mg合金中加入稀土Y也可使合金的力学性能得到一定提高,在加入0.2%Y后,合金的抗拉强度、屈服强度、伸长率、硬度均达到最大值,比未添加Y时分别提高了12.8%、17.2%、31.9%、9.6%。Y在加入合金后会吸附在Si生长台阶上,改变Si的生长方式,使共晶Si转变为颗粒状。此外,加入Y后,还可以提高合金的耐腐蚀性。通过对新制备出的Al-3Ti-3B-1Y中间合金进行XRD、SEM、EDS分析可知在Al-3Ti-3B-1Y中存在着TiB_2、AlB2、TiA_l3和Ti4Al43Y6相,作为中间合金加入到Al-Si合金中后,各相所起到的形核作用其机理略有不同。当加入3%Al-3Ti-3B-1Y后,合金的晶粒得到明显细化,α-Al由于形核核心的增多所生成的晶粒也较细小,共晶Si同样转变为颗粒状,同时合金的力学性能得到提高,其抗拉强度提高了19.3%;屈服强度提高了28.3%;伸长率提高了65.1%;硬度提高了20.5%。热速处理可从工艺上改善Al-Si合金性能,细化变质处理通过加入外加形核剂来改善Al-Si合金性能,因此将两者复合,即采用熔体复合处理的方法来强化Al-Si合金。实验结果表明,最佳的熔体复合处理工艺为:首先对Al-9Si-0.5Mg合金在熔体温度为930℃时进行热速处理,待合金温度降到浇注温度760℃时,加入3%Al-3Ti-3B-1Y中间合金,保温后浇注。通过对不同强化方式的综合比较后发现,合金在经过熔体复合处理后,其综合力学性能最佳。此时,Al-9Si-0.5Mg合金的抗拉强度、屈服强度、硬度、伸长率与未处理的合金相比分别提高了31.2%、22.6%、25.6%和80.5%。α-Al晶粒与共晶Si也得到了较好的细化。在Al-1.2Mn合金中加入稀土Y以及Al-5Ti-1B中间合金都可使Al-1.2Mn合金的晶粒得到不同给程度的细化,尤其是加入Al-5Ti-1B中间合金后,Al-1.2Mn的晶粒由粗大枝晶转变为尺寸较小的等轴状晶粒,合金中第二相粒子也变小,形貌改变,粗大骨骼状第二相减少。同时Al-1.2Mn的强度得到稍许提升,但伸长率提高较大,合金塑性较好。在加入Mg、Si后,Al-1.2Mn合金的强度提高幅度很大,但伸长率急剧降低,合金的塑性变差。当Si加入量较高时,会与Fe形成骨骼状α-Al12(FeMn)3Si相,影响合金性能,必须严格控制Mg、Si加入量。为提高合金的塑性,在Mg、Si强化后的Al-1.2Mn合金中加入Al-5Ti-1B中间合金后,合金的强度继续提高,伸长率略有降低,但仍可保持在20%以上,此时制备出的合金在具有高强度的同时保持了良好的塑性。Mg、Si及Al-5Ti-1B的最佳加入量分别为0.5%、0.3%和2%,此时合金的抗拉强度达到156MPa、屈服强度达到64MPa、硬度达到了52HB,分别提高了35.6%、28.1%、40.5%,而伸长率达到21.5%,各项力学性能指标均达到所需要求。这主要是由于在加入Al-5Ti-1B后,其中的TiA_l3和TiB_2粒子为合金晶粒提高了大量的形核质点。
[Abstract]:Aluminum alloy has been developed into second big metal materials except iron and steel, although it has been used in a large range of industry, its development speed can be seen. The application of aluminum alloy plays a great role in the light weight of the automobile. The use of cast aluminum alloy instead of the original steel material can not only reduce the overall quality of the automobile, but also can be used to reduce the overall quality of the automobile. In the deformed aluminum alloy, aluminum, aluminum, aluminum and other aluminum materials are widely used in construction, packaging, machinery and other aspects. At present, because of the low strength of the aluminum alloy, the development of aluminum alloy is seriously restricted. Therefore, the development of new components and new technology of high strength aluminum alloy has become the top priority of the present research. Some methods of strengthening the strength of the cast Al-Si alloy are studied. The other is based on the development of the high performance aluminum sheet material. The strength of Al-Mn alloy can be improved and its good plasticity is maintained. In this paper, the tensile test, metallographic microscope, polarizing microscope, scanning electron microscope and energy spectrum analysis, X The effects of alloying, refinement, heat speed treatment and melt composite treatment on Al-Si and Al-Mn alloys were studied by ray diffraction, electrochemical corrosion and thermal analysis. The matrix composition of Al-Si alloy was determined by Al-9Si-0.5Mg. using differential scanning calorimetry (DSC), and the melt structure transition at 855~885 C was found. The thermal speed treatment temperature of Al-9Si-0.5Mg alloy is 830 C ~990 C. The results show that the mechanical properties and microstructure of the alloy also change with the change of the melt temperature during the heat treatment. When the melt temperature reaches 930 C and 20min, the melt temperature drops to the pouring temperature (760 degrees C) when the cold material is added. The tensile strength, yield strength, hardness and elongation of the alloy increased by 24.3%, 37.7%, 82.9%, respectively, while the tensile strength, yield strength, hardness and elongation of the alloy increased by 24.3%, 37.7%, 82.9%. The eutectic Si was transformed from a long needle to granular, and the eutectic Si was transformed from a long needle to granular, and the heat was visible. With the addition of rare earth Y in Al-9Si-0.5Mg alloy, the mechanical properties of the alloy can be improved. After adding 0.2%Y, the tensile strength, yield strength, elongation and hardness of the alloy reached the maximum, which increased by 12.8%, 17.2%, 31.9%, respectively, when the alloy was added to the alloy, and 9.6%.Y was added to the alloy. Then it will adsorb on the Si growth step, change the growth mode of Si and change the eutectic Si into granular. In addition, after adding Y, the corrosion resistance of the alloy can be improved. By the XRD, SEM, EDS analysis of the newly prepared Al-3Ti-3B-1Y intermediate alloy, TiB_2, AlB2, TiA_l3, and facies are found in Al-3Ti-3B-1Y as intermediate alloy. After adding to Al-Si alloy, the mechanism of nucleation of each phase is slightly different. When 3%Al-3Ti-3B-1Y is added, the grain of the alloy is obviously refined, and the grain of alpha -Al is smaller because of the increase of nucleation core, and the eutectic Si is also transformed into granular, and the mechanical properties of the alloy are improved and the tensile strength of the alloy is improved. The yield strength was 19.3%, the yield strength increased by 28.3%, the elongation increased by 65.1%, and the hardness improved 20.5%. heat speed treatment can improve the properties of Al-Si alloy from the process, refining the modification treatment by adding external nucleating agent to improve the performance of Al-Si alloy. Therefore, the combination of the two, that is, the method of melt composite treatment to strengthen the Al-Si alloy. The optimum melt treatment process is as follows: first, the Al-9Si-0.5Mg alloy is treated by heat treatment at the melt temperature of 930 C. When the temperature of the alloy is reduced to the pouring temperature of 760 C, the 3%Al-3Ti-3B-1Y intermediate alloy is added to the alloy to be cast after heat preservation. After the comprehensive comparison of the different strengthening methods, it is found that the alloy is treated after the melt compound treatment. At this time, the tensile strength, yield strength, hardness and elongation of Al-9Si-0.5Mg alloy increased by 31.2%, 22.6%, 25.6% and 80.5%. alpha -Al grain and eutectic Si, respectively. The addition of Y and Al-5Ti-1B intermediate alloy to Al-1.2Mn alloy can make Al-1.2Mn alloy. After adding Al-5Ti-1B intermediate alloy, the grain of Al-1.2Mn is changed from coarse dendrite to smaller size, and the second phase particles in the alloy also become smaller, the morphology changes, and the second phase of the coarse skeleton decreases. At the same time, the strength of the Al-1.2Mn is slightly enhanced, but the elongation increases greatly. The strength of gold is better. After adding Mg and Si, the strength of Al-1.2Mn alloy is greatly increased, but the elongation of the alloy decreases sharply and the plasticity of the alloy becomes worse. When the amount of Si is high, it will form a skeletal alpha -Al12 (FeMn) 3Si phase with Fe, which affects the alloy properties. It is necessary to strictly control the Mg and Si addition. After adding Al-5Ti-1B intermediate alloy in gold, the strength of the alloy continues to increase and the elongation is slightly lower, but it can still remain above 20%. At this time, the alloy has a good plastic.Mg while the best addition of Si and Al-5Ti-1B is 0.5%, 0.3% and 2% respectively. The tensile strength of the alloy reaches 156MPa, and the yield is strong. The degree of hardness reached 64MPa, the hardness reached 52HB, increased by 35.6%, 28.1%, 40.5% respectively, and the elongation reached 21.5%. All the mechanical properties reached the required requirements. This was mainly due to the increase of TiA_l3 and TiB_2 particles in the alloy after the addition of Al-5Ti-1B, which increased a large number of nucleation particles.

【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG146.21

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