【作者】 孙小平；

【导师】 管仁国； 温景林；

【作者基本信息】 东北大学 ， 材料加工工程， 2011， 硕士

【摘要】 晶粒细化是改善材料力学性能,提高材料质量的重要手段。目前,Al-Ti-B合金线材是铝工业中使用最多的晶粒细化剂,然而国内生产的Al-Ti-B合金与国外产品质量相比,还存在一定的差距,主要体现在合金纯净度以及第二相化合物粒子TiAl3、TiB2的形态、大小、分布等方面问题,难以满足高质量的铝板、带、箔及型材生产的需求。而且随着我国铝加工工业的发展,对Al-Ti-B合金晶粒细化剂提出了更高要求。因此,研究开发高品质Al-Ti-B合金晶粒细化剂,对我国铝加工工业发展具有重要意义。本文结合广东省产业共性技术重大科技专项,以制备高品质Al-5Ti-1B合金线材为目标,研究了Al-5Ti-1B合金的制备及其线材的连续铸挤成形,主要工作及研究结果如下：(1)通过对Al-5Ti-1B合金熔体反应机理的分析与合金制备实验的研究,明确了工艺条件对合金组织的影响规律,优化了熔体制备工艺参数。其最佳工艺为氟盐加入比计算量增加5%；加料顺序为先加部分K2TiF6,再加K2TiF6和KBF4混合料；反应温度为860-890℃；反应时间为60-80min；合金化反应过程中加强搅拌。(2)通过对中间包内Al-5Ti-1B合金熔体的电磁搅拌,有效控制了线材成形后合金中的化合物颗粒分布的均匀性,消除聚集与沉淀现象,提高材料的纯净度。搅拌温度直接影响粘滞力的大小,搅拌温度升高有利于化合物颗粒的均匀分布,消除团聚带；电磁搅拌使TiAl3颗粒出现圆化现象；合金熔体最佳电磁搅拌温度为800℃,最佳搅拌时间为30min。(3)利用连续铸挤设备对Al-5Ti-1B合金进行铸挤成形,获得组织优良,表面光洁,无横向周期裂纹的合金线材。铸挤过程中的剪切搓动作用,可以使TiAl3颗粒发生边部剥落和沿裂纹脆断,从而使铸挤出的合金线材组织中化合物颗粒分布均匀,TiAl3呈颗粒块状,尺寸均在30-75μm,TiB2颗粒细小且均匀分散在TiAl3颗粒周围。最佳铸挤工艺为：铸挤温度为800℃；浇注流量为200-250K/h；冷却水流量为10-15L/min;铸挤轮转速为15r/min。(4)通过Al-5Ti-1B合金线材对纯铝细化效果的实验研究,明确了合金组织、细化温度及细化时间对细化效果的影响规律。最佳细化温度为690-710℃,最佳细化时间为0.5-30min。进一步明确了Al-5Ti-1B合金细化剂的最佳组织为：TiAl3颗粒为带棱角的块状,尺寸在30μm左右,TiB2颗粒为细小弥散分布,大小在0.5-1.0μm。(5)通过优化制备工艺、电磁搅拌工艺、线材成形工艺制备出了Al-5Ti-1B合金线材,其成分与组织符合高品质细化剂的要求。经过现场工业应用试验,其细化效果与国外同类产品的细化效果相当。更多还原

【Abstract】 Grain refinement is an important tool to improve the mechanical properties and the quality of materials. Currently, Al-Ti-B alloy wire used in aluminum industry is the largest grain refiner. However, due to its low purity, poor shape, size, and distributions of the second phase compound particles of TiAl3and TiB2, Al-Ti-B alloy wire is difficult to meet the requirements of production of high quality aluminum plate, strip, foil and profiles. This is the main disparity compared with the foreign products. Along with the development of aluminum processing industry, the more high quality of Al-Ti-B alloy has been required. Furthermore, there is an important significance in the development of aluminum processing industry to development high quality Al-Ti-B alloy of grain refiner.In this paper, to prepare high quality Al-5Ti-1B for goals, according to the industrial generic technology and grand science and technology special project of Guangdong province, the alloy preparation and wire Continues Casting and Extrusion (CASTEX) forming of Al-5Ti-1B were studied. Main work and results are as follows:(1) The effects law of the preparation process conditions on microstructure of Al-5Ti-1B alloy were obtained and the melt preparation process parameters were optimized by analyse of the melt reaction mechanism of Al-5Ti-1B alloy and study experiment of melt preparation. The optimal technological parameters were obtained as follows. The addition amount of villiaumite is more than5%to normal amount of calculation; the adding order of villiaumite is adding part of K2TiF6firstly and then adding K2TiF6and KBF4mixture; the reaction temperature is860-890℃; the reaction time is60-80min; alloying reaction need violent stirring.(2) The uniformity distribution of compounds particles in the alloy was effectively controlled after wire forming; the accumulation and precipitation of compounds particles were eliminated; melt purity of Al-5Ti-1B alloy was improved by electromagnetic stirring to Al-5Ti-1B alloy melt in the tundish. Temperature directly influences the viscous force, increasing electromagnetic stirring temperature make for uniform distribution of compounds particles and aggregate banding disappeared. Under the action of the electromagnetic stirring particles of TiAl3appear sleek round phenomenons. The best electromagnetic stirring temperature is800℃, stirring time is30min.(3) By using the Continues Casting and Extrusion (CASTEX) equipment to casting and extrusion forming, the alloy wires of Al-5Ti-1B which have advantages in good microstructure, smooth surface and no lateral cycle crack were obtained. Shear and rub moves function was strengthen in casting and extrusion process, which can cause spalling of edge and brittle fracture along the crack for TiAl3particles, finally, the compounds particles distribution in microstructure of alloy wire become uniform. The structures of TiAl3particle are massive and all the size is30-75μm. The structures of TiB2particle are small and evenly dispersing around TiAl3particles. The optimal processing parameters of Continues Casting and Extrusion (CASTEX) are as follows. Casting and extrusion temperature is800℃, pouring flow is200-250Kg/h, Volume of cooling water flow is10-15L/min, casting extrusion wheel speed is15r/min.(4) The effects law of microstructure of Al-5Ti-1B alloy, refinement temperature and refinement time on refining effect were obtained by study experiment of Al-5Ti-1B alloy wire on refining effect of pure aluminium. The optimal refinement temperature is690-710℃. The optimal refinement time is0.5-30min. It is further explicated that the optimal microstructure are angulatus massive, the size is30μm, the structures of TiB2particle are small and evenly dispersed, the size is0.5-1.0μm.(5) The composition and microstructure of Al-5Ti-1B alloy wires which are prepared by optimizing technological conditions of preparation, electromagnetic stirring and wire forming meet requirements of the high quality grain refiner. Through application test in industrial field the refinement effects of Al-5Ti-1B alloy wires are the same as imported similar products.更多还原