铝合金焊接材料洁净度表征及增熵劣化研究

发布时间：2018-05-13 08:08

本文选题：铝镁焊料 + 杂质元素　；参考：《机械科学研究总院》2016年博士论文

【摘要】：铝合金焊料的洁净度是铝合金焊接接头可靠性的重要保障。为生产高性能洁净铝合金焊料,拓展铝合金的应用领域,本文在Al-5Mg-0.1Mn-0.1Cr-0.1Ti焊料的基础上系统研究了Fe、Si、Ca杂质元素及Sc、La、Ce稀土元素在合金中的行为及对焊料性能的影响。在Al-5Mg合金的基础上研究了Fe与Sc、La、Ce,Si/Ca与Sc、La、Ce的交互耦合作用,及杂质与稀土共同存在时引起的焊料和焊接接头组织与性能的变化。根据试验结果,给出了焊料洁净度表征公式,并探讨了杂质元素的增熵劣化原理,提出了抑制杂质劣化性能措施,得到以下结论：(1)杂质与稀土在铝镁焊料中行为研究：Fe在铸态铝合金中形成粗大针状富Fe相θ-AlFe3,降低了合金强度、塑性和冲击断裂韧性。为获得良好的焊料性能,焊料中Fe应控制在0.2%(质量分数)以下。Si对焊料强度影响较小,但劣化焊料塑性和韧性。随着Si含量的提高,合金由韧性断裂转变为以脆性断裂为主的混合型断裂,0.5% Si为合金韧脆转变的临界点。为保证焊料良好的塑韧性,焊料中的Si应小于0.25%或更低。Ca在焊料中以块状(Cr,Ti)2Ca(Al,Mg)20口不连续条状Al2Ca化合物在晶界富积析出。Ca元素改变了合金断裂方式,合金拉伸或冲击断口由穿晶延性断裂特征(Ca0.28%)转变为脆性断裂(Ca0.28%)特征,合金韧脆转变点Ca含量为0.28%。为获得好的综合力学性能,应尽量降低合金中Ca的含量。焊料中存的杂质生成了有害相,降低了焊料洁净度,劣化了焊料性能。焊料中Sc细化a-A1晶粒,使连续分布在晶界的条状β-Al3Mg2转变为链球状并断续分布在晶界,Sc加入提高了焊料强度和塑韧性。La除了固溶在焊料合金基体内,还以块状或枝状(Cr,Ti)2La(Al,Mg)20稀土化合物和棒状或颗粒状Al11La3化合物形式存在。微量添加La时,合金晶粒细化,强度和塑韧性提高。但随La添加量的增加(大于0.45%),析出的块状和粗大枝状富La化合物降低了晶粒细化对合金性能的优化作用,使合金性能下降。Ce以块状(Cr,Ti)2Ce(Al,Mg)20化合物和棒状α-Ce3Al11化合物形式在晶界和相界分布,并随Ce的增加而增加。Ce的固溶强化和晶粒细化作用使合金强度和塑韧性良好,但块状(Cr,Ti)2Ce(Al,Mg)20化合物对焊料性能有剧烈的劣化作用。微量稀土添加到焊料中,因固溶、细化、变质和有益第二相生成,可优化焊料与焊接接头性能,但应控制稀土的添加量,防止有害稀土相生成。(2)杂质与稀土元素交互作用研究：Sc与Fe无强烈的交互作用,Sc加入不改变Fe相的分布与形貌,Sc对富Fe相没有明显的变质作用。杂质Fe劣化了焊接接头的力学性能,Sc不改变Fe在铝中的行为及Fe致性能劣化。与含有微量Fe(～0.16%)的Al-Mg-xLa相比,Al-Mg-Fe-xLa中La对富Fe相有变质作用,Al-Mg-Fe(～0.8%)-xLa焊接接头力学性能与Al-Mg-xLa接近。由于La与Fe的交互作用,La加入可抑制Fe对焊接接头力学性能的劣化。高Fe含量的Al-5Mg焊接接头中Ce的存在形式有四种。固溶在a-Al晶粒内；以化合物Al11Ce3的形式偏聚在晶界；Ce吸附在富Fe相表面；Ce存在于富Fe相内部,形成(AlFeSiCe)化合物。Fe与Ce强烈的交互作用和Ce对富Fe相进行的变质,使Ce抑制了Fe对焊接接头性能的劣化。Al-5Mg焊料中Sc与Mg2Si弱交互作用,Sc不改变Si对焊接接头性能劣化。La与Si交互作用促使La对Mg2Si相变质,使Al-Mg-Si焊接接头抗拉强度因Si致劣化程度减弱。但Al-Mg-Si焊接接头脆性大,La添加后焊接接头冲击韧性没有明显改观。La不能明显抑制Al-Mg-Si焊接接头Si致韧性劣化。Ce与Si及Mg2 Si的交互作用,使Ce对α-Al晶粒和Mg2Si有细化作用,故Ce可抑制焊接接头因Si导致的强度劣化,但因Ce在合金中能形成粗大的Al11Ce3和AlFeSiCe,焊接接头冲击韧性没有改善,过量添加Ce后焊接接头抗拉强度和冲击韧性均下降。Ce与Si的作用强度小于La与Si的作用强度,而Ce与Al的作用强度远大于La与Al的作用强度,故Ce更倾向于与Al形成化合物。Ce对Mg2Si的变质弱于La对Mg2Si的变质。Ca与Sc无明显的交互作用,但Ca能改变Sc在Al中的固溶度,促进Al3Sc粒子的聚积。Sc添加不改变Ca引起的焊接接头性能劣化。Ca与La有微弱交互作用,Ca与La不形成化合物,Ca与La可互溶于对方晶格,La不改变富Ca化合物结构与形貌,La对富Ca相无明显的变质,且La不改变Ca导致的焊接接头性能劣化。Ce与Ca微弱的作用力,将Ce添加到含Ca的焊料内,Ce不改变Ca对焊接接头性能的劣化,Ce单独优化焊接接头性能。Ce对Ca的作用与La对Ca的作用不同,Ca与La可微弱互溶形成固溶体,而Ce与Ca基本无互溶。(3)铝合金焊料洁净度表征体系与增熵劣化研究：洁净度表征公式：多元交互作用值)焊料中杂质元素增加,增加了系统熵值,焊料洁净度降低,导致焊料与焊接接头性能劣化。添加有益元素降低系统熵值,净化合金,有益元素抑制杂质对焊料和焊接接头性能的劣化。
[Abstract]:The cleanliness of aluminum alloy solder is an important guarantee for the reliability of aluminum alloy welding joint. In order to produce high performance clean aluminum alloy solder and expand the application field of aluminum alloy, the behavior of Fe, Si, Ca impurity elements and Sc, La, Ce elements in the alloy and the performance of the solder are systematically studied on the basis of Al-5Mg-0.1Mn-0.1Cr-0.1Ti solder. On the basis of Al-5Mg alloy, the interaction between Fe and Sc, La, Ce, Si/Ca and Sc, La, Ce, and the change of microstructure and properties of solder and welded joint caused by the common presence of impurities and rare earth were studied. According to the test results, the expression of the cleanliness of the solder was given, and the principle of entropy deterioration of the impurity elements was discussed and the suppression of the impurity elements was discussed. The following conclusions are obtained as follows: (1) study on the behavior of impurities and rare earth in aluminum and magnesium solder: Fe formed a coarse needle like rich Fe phase in the cast aluminum alloy, which reduced the strength, plasticity and impact fracture toughness of the alloy. In order to obtain good solder properties, Fe should be controlled under 0.2% (mass fraction) of.Si pair solder in the solder. The strength has little effect, but the plasticity and toughness of the deteriorated solder. With the increase of Si content, the alloy changes from ductile fracture to brittle fracture, and 0.5% Si is the critical point of the alloy ductile and brittle transition. In order to ensure the good plasticity of the solder, the Si in solder should be less than 0.25% or lower.Ca in bulk (Cr, Ti) 2Ca (Al, Mg) 20 in the solder. The fracture mode of the alloy is changed by.Ca element in the grain boundary, and the tensile or impact fracture of the alloy is changed from the characteristic of transgranular ductile fracture (Ca0.28%) to brittle fracture (Ca0.28%), and the Ca content of the ductile brittle transition point of the alloy is 0.28%. as a good comprehensive mechanical property, and the content of Ca in the alloy should be reduced as much as possible. The impurity deposited in the solder produces a harmful phase, reducing the cleanliness of the solder and deteriorating the performance of the solder. Sc refines the a-A1 grain in the solder and makes the continuous distribution of the bar shaped beta -Al3Mg2 in the grain boundary to the grain boundary and intermittently in the grain boundary. The Sc addition improves the solder strength and the plasticity of.La in addition to the solid solution in the solder alloy matrix, and is also lumped or branch. Cr, Ti) 2La (Al, Mg) 20 rare earth compounds and rod like or granular Al11La3 compounds exist. When the La is added, the grain refinement, strength and ductility of the alloy are improved. But with the addition of La (greater than 0.45%), the precipitated lump and coarse branch like rich La compounds reduce the optimization of grain refinement to alloy properties and make alloying. It can decrease.Ce in the form of block (Cr, Ti) 2Ce (Al, Mg) 20 compound and rod like alpha -Ce3Al11 in the grain boundary and phase boundary, and increases the solid solution strengthening and grain refinement with the increase of Ce, which makes the alloy strength and ductility good. But the bulk (Cr, Ti) 2Ce (Cr, Ti) 20 compounds have severe deterioration of the solder properties. Trace rare earth addition Adding to the solder, because of solid solution, refinement, metamorphism and beneficial second phase formation, the performance of solder and welded joint can be optimized, but the addition of rare earth should be controlled to prevent the formation of harmful rare earth phase. (2) the interaction of impurities and rare earth elements: Sc and Fe have no strong interaction, Sc addition does not change the distribution and morphology of the Fe phase, and Sc has no Fe phase. The impurity Fe deteriorates the mechanical properties of the welded joint, and Sc does not change the behavior of Fe in aluminum and the deterioration of the properties of Fe. Compared with Al-Mg-xLa containing a trace Fe (to 0.16%), La has a metamorphic effect on the rich Fe phase in Al-Mg-Fe-xLa, and the mechanical properties of Al-Mg-Fe (~ 0.8%) -xLa welding joints are close to that of Al-Mg-xLa. Use, La addition can inhibit the deterioration of mechanical properties of the welded joint of Fe. There are four forms of Ce in the Al-5Mg welded joint with high Fe content. Solid solution is in the grain of a-Al; Al11Ce3 in the form of compound Al11Ce3; Ce adsorbed on the rich Fe phase surface; Ce exists in the rich Fe phase, and the form (AlFeSiCe) compounds interact strongly with them. The deterioration of the rich Fe phase by using and Ce makes Ce inhibit the weak interaction between Sc and Mg2Si in the deterioration of the welding joint properties of the welding joint. Sc does not change the Si's interaction between.La and Si on the performance of the welding joint, which causes the La to deteriorate. The impact toughness of the welded joint after the addition of La does not obviously change the effect of.La on the interaction between.Ce and Si and Mg2 Si caused by the Al-Mg-Si welding joint Si, so that Ce can refine the grain and Mg2Si of the alpha -Al, so that Ce can inhibit the strength deterioration caused by the welding joint. SiCe, the impact toughness of the welded joint was not improved. The tensile strength and the impact toughness of the welded joint decreased after the excessive addition of Ce. The action strength of.Ce and Si was less than the action strength of La and Si, while the action strength of Ce and Al was much greater than that of La and Al, so Ce tended to deteriorate with the formation of Al. There is no obvious interaction between Ca and Sc, but Ca can change the solid solubility of Sc in Al, promote the accumulation of Al3Sc particles in the accumulation of.Sc without changing Ca, and the performance deterioration of the welding joint is weak interaction with La. Ca and La do not form compounds. And La does not change the welding joint properties caused by Ca to deteriorate the weak force of.Ce and Ca, and adding Ce to the solder containing Ca, Ce does not change the deterioration of the performance of the welded joint by Ca. Ce alone optimizes the performance of the welding joint performance of.Ce to Ca. (3) the characterization system of cleanliness of aluminum alloy solder and the study of entropy deterioration: purity characterization formula: multiple interaction value) the impurity elements in the solder increase, increase the entropy value of the system, reduce the cleanliness of the solder and lead to the deterioration of the performance of the solder and welding joint. Deterioration of the performance of solder and welded joints.

【学位授予单位】：机械科学研究总院
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG42

【相似文献】