本文選題：鋁鎂焊料 + 雜質(zhì)元素�。� 參考：《機(jī)械科學(xué)研究總院》2016年博士論文

【摘要】：鋁合金焊料的潔凈度是鋁合金焊接接頭可靠性的重要保障。為生產(chǎn)高性能潔凈鋁合金焊料,拓展鋁合金的應(yīng)用領(lǐng)域,本文在Al-5Mg-0.1Mn-0.1Cr-0.1Ti焊料的基礎(chǔ)上系統(tǒng)研究了Fe、Si、Ca雜質(zhì)元素及Sc、La、Ce稀土元素在合金中的行為及對焊料性能的影響。在Al-5Mg合金的基礎(chǔ)上研究了Fe與Sc、La、Ce,Si/Ca與Sc、La、Ce的交互耦合作用,及雜質(zhì)與稀土共同存在時引起的焊料和焊接接頭組織與性能的變化。根據(jù)試驗(yàn)結(jié)果,給出了焊料潔凈度表征公式,并探討了雜質(zhì)元素的增熵劣化原理,提出了抑制雜質(zhì)劣化性能措施,得到以下結(jié)論：(1)雜質(zhì)與稀土在鋁鎂焊料中行為研究：Fe在鑄態(tài)鋁合金中形成粗大針狀富Fe相θ-AlFe3,降低了合金強(qiáng)度、塑性和沖擊斷裂韌性。為獲得良好的焊料性能,焊料中Fe應(yīng)控制在0.2%(質(zhì)量分?jǐn)?shù))以下。Si對焊料強(qiáng)度影響較小,但劣化焊料塑性和韌性。隨著Si含量的提高,合金由韌性斷裂轉(zhuǎn)變?yōu)橐源嘈詳嗔褳橹鞯幕旌闲蛿嗔?0.5% Si為合金韌脆轉(zhuǎn)變的臨界點(diǎn)。為保證焊料良好的塑韌性,焊料中的Si應(yīng)小于0.25%或更低。Ca在焊料中以塊狀(Cr,Ti)2Ca(Al,Mg)20口不連續(xù)條狀A(yù)l2Ca化合物在晶界富積析出。Ca元素改變了合金斷裂方式,合金拉伸或沖擊斷口由穿晶延性斷裂特征(Ca0.28%)轉(zhuǎn)變?yōu)榇嘈詳嗔?Ca0.28%)特征,合金韌脆轉(zhuǎn)變點(diǎn)Ca含量為0.28%。為獲得好的綜合力學(xué)性能,應(yīng)盡量降低合金中Ca的含量。焊料中存的雜質(zhì)生成了有害相,降低了焊料潔凈度,劣化了焊料性能。焊料中Sc細(xì)化a-A1晶粒,使連續(xù)分布在晶界的條狀β-Al3Mg2轉(zhuǎn)變?yōu)殒溓驙畈嗬m(xù)分布在晶界,Sc加入提高了焊料強(qiáng)度和塑韌性。La除了固溶在焊料合金基體內(nèi),還以塊狀或枝狀(Cr,Ti)2La(Al,Mg)20稀土化合物和棒狀或顆粒狀A(yù)l11La3化合物形式存在。微量添加La時,合金晶粒細(xì)化,強(qiáng)度和塑韌性提高。但隨La添加量的增加(大于0.45%),析出的塊狀和粗大枝狀富La化合物降低了晶粒細(xì)化對合金性能的優(yōu)化作用,使合金性能下降。Ce以塊狀(Cr,Ti)2Ce(Al,Mg)20化合物和棒狀α-Ce3Al11化合物形式在晶界和相界分布,并隨Ce的增加而增加。Ce的固溶強(qiáng)化和晶粒細(xì)化作用使合金強(qiáng)度和塑韌性良好,但塊狀(Cr,Ti)2Ce(Al,Mg)20化合物對焊料性能有劇烈的劣化作用。微量稀土添加到焊料中,因固溶、細(xì)化、變質(zhì)和有益第二相生成,可優(yōu)化焊料與焊接接頭性能,但應(yīng)控制稀土的添加量,防止有害稀土相生成。(2)雜質(zhì)與稀土元素交互作用研究：Sc與Fe無強(qiáng)烈的交互作用,Sc加入不改變Fe相的分布與形貌,Sc對富Fe相沒有明顯的變質(zhì)作用。雜質(zhì)Fe劣化了焊接接頭的力學(xué)性能,Sc不改變Fe在鋁中的行為及Fe致性能劣化。與含有微量Fe(～0.16%)的Al-Mg-xLa相比,Al-Mg-Fe-xLa中La對富Fe相有變質(zhì)作用,Al-Mg-Fe(～0.8%)-xLa焊接接頭力學(xué)性能與Al-Mg-xLa接近。由于La與Fe的交互作用,La加入可抑制Fe對焊接接頭力學(xué)性能的劣化。高Fe含量的Al-5Mg焊接接頭中Ce的存在形式有四種。固溶在a-Al晶粒內(nèi)；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相內(nèi)部,形成(AlFeSiCe)化合物。Fe與Ce強(qiáng)烈的交互作用和Ce對富Fe相進(jìn)行的變質(zhì),使Ce抑制了Fe對焊接接頭性能的劣化。Al-5Mg焊料中Sc與Mg2Si弱交互作用,Sc不改變Si對焊接接頭性能劣化。La與Si交互作用促使La對Mg2Si相變質(zhì),使Al-Mg-Si焊接接頭抗拉強(qiáng)度因Si致劣化程度減弱。但Al-Mg-Si焊接接頭脆性大,La添加后焊接接頭沖擊韌性沒有明顯改觀。La不能明顯抑制Al-Mg-Si焊接接頭Si致韌性劣化。Ce與Si及Mg2 Si的交互作用,使Ce對α-Al晶粒和Mg2Si有細(xì)化作用,故Ce可抑制焊接接頭因Si導(dǎo)致的強(qiáng)度劣化,但因Ce在合金中能形成粗大的Al11Ce3和AlFeSiCe,焊接接頭沖擊韌性沒有改善,過量添加Ce后焊接接頭抗拉強(qiáng)度和沖擊韌性均下降。Ce與Si的作用強(qiáng)度小于La與Si的作用強(qiáng)度,而Ce與Al的作用強(qiáng)度遠(yuǎn)大于La與Al的作用強(qiáng)度,故Ce更傾向于與Al形成化合物。Ce對Mg2Si的變質(zhì)弱于La對Mg2Si的變質(zhì)。Ca與Sc無明顯的交互作用,但Ca能改變Sc在Al中的固溶度,促進(jìn)Al3Sc粒子的聚積。Sc添加不改變Ca引起的焊接接頭性能劣化。Ca與La有微弱交互作用,Ca與La不形成化合物,Ca與La可互溶于對方晶格,La不改變富Ca化合物結(jié)構(gòu)與形貌,La對富Ca相無明顯的變質(zhì),且La不改變Ca導(dǎo)致的焊接接頭性能劣化。Ce與Ca微弱的作用力,將Ce添加到含Ca的焊料內(nèi),Ce不改變Ca對焊接接頭性能的劣化,Ce單獨(dú)優(yōu)化焊接接頭性能。Ce對Ca的作用與La對Ca的作用不同,Ca與La可微弱互溶形成固溶體,而Ce與Ca基本無互溶。(3)鋁合金焊料潔凈度表征體系與增熵劣化研究：潔凈度表征公式：多元交互作用值)焊料中雜質(zhì)元素增加,增加了系統(tǒng)熵值,焊料潔凈度降低,導(dǎo)致焊料與焊接接頭性能劣化。添加有益元素降低系統(tǒng)熵值,凈化合金,有益元素抑制雜質(zhì)對焊料和焊接接頭性能的劣化。
[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.

【學(xué)位授予單位】：機(jī)械科學(xué)研究總院
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG42

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