【作者】 李青松；

【导师】 罗震；

【作者基本信息】 天津大学 ， 材料加工工程， 2007， 硕士

【摘要】 铝合金因重量轻、资源丰富、综合性能好,所以在机械、交通运输、航天与军事工业等高新技术领域中的应用逐年增加。铝合金的电阻点焊是汽车车身自动化生产中最重要的焊接工艺方法,但是铝合金电阻点焊中存在的一个主要问题就是熔核焊点强度差,影响使用效率。因此,研究铝合金点焊熔核设计至关重要。电阻点焊是应用最广的焊接方法之一。有关熔核形成理论及点焊质量控制技术的研究始终是该领域的前沿和主要热点。本文通过对铝合金点焊熔核孕育过程的研究发现,控制其组织和性能的关键之一是得到细小均匀的等轴晶。晶粒细化是近期国际上对传统材料升级和创造新型合金的工艺手段之一。因此,可运用不同的晶粒细化方法来获得细小的等轴晶,即结晶组织的微细化处理。中间合金对铝合金优异的细化效果,使得它在工业生产上得到广泛的使用。但是,由于中间合金制备过程或加入方式不同,导致其相的形态和分布不同,进而对铝合金产生不同的细化效果,这些中间合金制备工艺复杂,成本高。从铝合金工件表面考虑,在铝合金表面涂敷Ti、B2O3、Cr、Zr、Mn等材料,形成铝熔核中间合金晶粒细化剂,促进液体内部生核,产生大量的有效异质形核核心,获得等轴晶组织、细化晶粒、提高晶体的形核率,有效地阻止了微裂纹的聚集和长大。因此在拉伸载荷下,合金可以承受更大的变形,使得合金的塑性得到明显提高。实验证明,添加涂敷材料,等轴晶区域增大、晶粒细化,焊点强度最大可提高2/3。对Ti、B2O3、Cr、Zr、Mn等材料提高强度的机理分析表明:异质核心的产生、获得与晶核润湿角非常小的形核“基底”、等轴晶核的增殖、弥散析出相的形成,引起位错运动的阻力增加,提高了焊点的塑性,使焊点的抗剪拉能力得到明显提高。更多还原

【Abstract】 The aluminum alloys are widespread used in the machinery, the transportation, astronautics and the war industry and so on because of the light weight, the ample resources, overall good performance. The aluminum alloys resistance spot welding is most important welding technique in the automobile body automatic metaphase mid-production. But in the aluminum alloys resistance spot welding there is a problem that Spot intensity is bad and the use efficiency is low. Therefore research of the aluminum alloys spot welding fusion is very important.The resistance spot welding is one of broadest welding methods. The related spot forms the theory and the spot welding quality control technology research throughout the domain the main hotspot. Through the research of aluminum alloys spot welding fusion breeding process, I discovered that control one of its organization and performance keys is to obtain the tiny even isometric crystal. The crystal grain is the near future on international to the traditional material promotion and one of creation new alloys underbid craft methods. Therefore, to utilize the different crystal grain thin method to obtain the tiny isometric crystal, namely crystallization organization’s tiny processing.The intermediate alloys to the aluminum alloys outstanding thin effect enables it to obtain the widespread use in the industrial production. But because the intermediate alloys preparation process or joins the way differently, causes it to contain the shape and the distribution different, then has the different thin effect to the aluminum alloys, these intermediate alloys preparation crafts complex, the cost is high.Considered from the aluminum alloys work piece surface that, spreads in the aluminum alloys surface spreads material and so on Ti, B2O3, Cr, Zr, Mn, forms the aluminum melt nucleus intermediate alloys crystal grain thin medicinal preparation, has the massive effective nitrogen shape nuclear core, enhances the crystal the shape nucleus rate, thus thin crystal grain. Experiments show that adding coating materials increased regional axis crystal grain refinement, solder joint strength can be increased by 2 / 3.The analysis of Ti, B2O3, Zr, Cr, Mn shows that having a core of the heterogeneity, nuclei were wetting angle with very small form the nucleus "basal",equiaxed nuclei proliferation, diffusing the formation of precipitates caused the increased resistance movement, increase the plasticity of the spot. So that the solder joint shear rafah has been markedly enhanced ability更多还原