6061和4043铝合金在不同金属表面的润湿行为及界面结构
发布时间：2019-04-16 15:44
【摘要】：铝合金以其优良的抗氧化性能而被广泛应用于热浸镀工艺中的镀层材料。以钢和钛作为基体,通过热浸铝工艺得到的镀层不但可以实现材料表面的室温抗腐蚀性而且可以提高材料高温下的抗氧化性。而在铜表面热浸镀铝并结合半固态连接可以避免Al-Cu连接过程中过多脆性相的产生,实现Al-Cu复合材料的有效连接。热浸铝工艺的实现及镀层质量的控制与铝合金在基体表面的润湿性密切相关。同时异种金属连接过程中钎料对母材良好的润湿性是获得优质焊接接头的重要因素之一。因此,本课题通过研究铝合金与T2铜、Q235钢、TC4钛合金及TA2纯钛的润湿行为及界面结构,探讨界面反应与润湿性及铺展动力学间的相互联系。研究内容有望进一步丰富上述基体热浸铝工艺及异种金属连接过程中钎料对母材润湿性的相关基础理论。首先,研究了熔融6061和4043铝合金分别在T2铜表面的润湿行为,研究表明:该体系属于典型的溶解润湿,在650~700 oC,润湿性与温度存在典型的相互依赖,随着温度升高最终润湿性逐渐改善;在700~750 oC,随着温度升高润湿性无明显改善,最终平衡接触角均在21o左右;界面分层现象可由溶解析出理论解释,整个界面呈三层,依次为α2 Al-Cu固溶体、δAl-Cu固溶体及AlCu金属间化合物;三相线区域熔融铝合金含量相对较少,随着Cu的溶解更容易达到饱和,并析出金属间化合物;金属间化合物产生后阻碍三相线区域固-液界面物质交流,同时阻碍熔滴铺展,从而抑制润湿;两者体系的铺展动力学均可由溶解过程控制润湿模型描述,6061和4043铝熔滴在基板表面呈非线性铺展,润湿激活能分别为52 kJ/mol和57 kJ/mol。其次,研究了熔融6061和4043铝合金在Q235钢、TC4钛合金及TA2纯钛表面的润湿行为,研究表明:上述体系均为典型的反应润湿,最终润湿性与温度存在典型的相互依赖关系,随着温度升高润湿性明显改善;铝合金中微量的Si、Mg导致界面结构及最终润湿性产生差异,Si在界面富集,并且满足热力学条件;界面处富Si的致密层(Fe2(Al1-xSix)5、Ti7Al5Si12)产生后阻碍三相线区域固-液界面物质交流,从而抑制润湿;而Ti7Al5Si12不稳定,随着温度升高,致密的Ti7Al5Si12逐渐分解,同时在三相线区域产生疏松的Al3Ti金属间化合物,疏松相的产生能够破除基板表面的氧化膜,促进铝合金熔滴与基板发生反应,从而促进润湿;Mg以蒸汽的形式挥发后包裹在三相线附近充当气相钎剂(还原剂),还原基板表面的氧化膜,使得基板表面呈金属性,熔滴与洁净的基板接触并发生反应,同时三相线区域产生疏松的FeAl3及Al3Ti,疏松相产生后能够破除基板表面的氧化膜,促进润湿;铺展动力学均可由典型的反应产物控制润湿模型描述,6061铝合金在Q235钢表面呈线性铺展,在TC4钛合金及TA2纯钛表面先呈非线性铺展,后呈线性铺展;而4043铝合金在Q235钢、TC4钛合金及TA2纯钛表面均以非线性铺展为主,润湿激活能与界面反应吉布斯自由能相关。最后,上述反应润湿体系均出现明显的前驱膜,前驱膜与温度存在相互依赖关系,温度越高前驱膜越宽;同时,前驱膜的出现总是伴随着较好的最终润湿性,形成机制为“皮下渗透”机制。
[Abstract]:The aluminum alloy is widely used in the coating material in the hot-dip coating process with its excellent oxidation resistance. By using the steel and the titanium as the matrix, the coating obtained by the hot-dip aluminum process not only can realize the room-temperature corrosion resistance of the surface of the material, but also can improve the oxidation resistance of the material at high temperature. And the hot-dip aluminizing on the surface of the copper and the semi-solid connection can avoid the generation of the excessive brittle phase in the Al-Cu connection process and realize the effective connection of the Al-Cu composite material. The realization of the hot-dip aluminum process and the control of the coating quality are closely related to the wettability of the aluminum alloy on the surface of the substrate. At the same time, the good wetting of the base material to the base metal during the connection of the dissimilar metal is one of the important factors to obtain the high-quality welded joint. In this paper, the wetting behavior and interface structure of aluminum alloy and T2 copper, Q235 steel, TC4 titanium alloy and TA2 pure titanium are studied, and the contact between the interface reaction and the wettability and the spreading dynamics is discussed. The research contents are expected to further enrich the basic theory of the wettability of the base metal in the hot-dip aluminum technology and the dissimilar metal connecting process. First, the wetting behavior of the molten 6061 and 4043 aluminum alloy on the surface of the T2 copper is studied. The results show that the system is typical of the dissolution and wetting, and the wettability and the temperature are typical in the range of 650-700 oC, and the wettability is gradually improved with the increase of the temperature. The final equilibrium contact angle is about 21 o as the temperature increase wettability is not obviously improved, and the interface layering phenomenon can be explained by the dissolution and precipitation theory, and the whole interface is three layers, and the whole interface is a 2-Al-Cu solid solution, an Al-Cu solid solution and an AlCu intermetallic compound; the content of the molten aluminum alloy in the three-phase line region is relatively small, and the saturation is more easily achieved with the dissolution of the Cu, and the intermetallic compound is precipitated; after the intermetallic compound is generated, the material exchange of the solid-liquid interface of the three-phase line region is prevented, and the droplet spreading is prevented, and the wetting is inhibited; The spreading kinetics of the two systems can be described by the dissolution process control and wetting model,6061 and 4043 aluminum droplets are non-linearly spread on the surface of the substrate, and the wetting activation energy is 52 kJ/ mol and 57 kJ/ mol, respectively. The wetting behavior of molten 6061 and 4043 aluminum alloy on the surface of Q235 steel, TC4 titanium alloy and TA2 pure titanium is studied. The results show that the system is typical of reactive wetting, and the final wettability and temperature are of typical interdependency, and the wettability is improved obviously with the increase of temperature. The micro-Si and Mg in the aluminum alloy lead to the difference of the interface structure and the final wettability, and the Si is rich in the interface, and the thermodynamic condition is satisfied; the Si-rich dense layer (Fe 2 (Al1-xSix)5, Ti7Al5Si12) at the interface blocks the material exchange of the solid-liquid interface of the three-phase line, thereby inhibiting the wetting; Ti7Al5Si12 is unstable, and as the temperature increases, the dense Ti7Al5Si12 is gradually decomposed, and a loose Al3Ti intermetallic compound is generated in the three-phase line region, and the formation of the loose phase can break the oxide film on the surface of the substrate, and promote the reaction between the molten drop of the aluminum alloy and the substrate, thereby promoting the wetting; The Mg is volatilized in the form of steam, and is wrapped in the vicinity of the three-phase line to act as a gas-phase entrainer (reducing agent), and the oxide film on the surface of the substrate is reduced, so that the surface of the substrate is metallic, the molten drop is in contact with the clean substrate and reacts, and simultaneously the three-phase line region produces loose FeAl3 and Al3Ti, the oxidation film on the surface of the substrate can be broken after the loose phase is generated, and the wetting is promoted; the spreading kinetics can be described by a typical reaction product control wetting model; the 6061 aluminum alloy is linearly spread on the surface of the Q235 steel; The surface of the 4043 aluminum alloy in Q235 steel, TC4 titanium alloy and TA2 pure titanium is mainly non-linear spread, and the wetting activation energy can be related to the Gibbs free energy of the interface reaction. Finally, the above-mentioned reaction wetting system has obvious precursor film, the precursor film and the temperature are interdependent, the higher the temperature is, the wider the precursor film is, and at the same time, the appearance of the precursor film is always accompanied by better final wettability, and the forming mechanism is the "Subcutaneous penetration" mechanism.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.44
本文编号：2458897
[Abstract]:The aluminum alloy is widely used in the coating material in the hot-dip coating process with its excellent oxidation resistance. By using the steel and the titanium as the matrix, the coating obtained by the hot-dip aluminum process not only can realize the room-temperature corrosion resistance of the surface of the material, but also can improve the oxidation resistance of the material at high temperature. And the hot-dip aluminizing on the surface of the copper and the semi-solid connection can avoid the generation of the excessive brittle phase in the Al-Cu connection process and realize the effective connection of the Al-Cu composite material. The realization of the hot-dip aluminum process and the control of the coating quality are closely related to the wettability of the aluminum alloy on the surface of the substrate. At the same time, the good wetting of the base material to the base metal during the connection of the dissimilar metal is one of the important factors to obtain the high-quality welded joint. In this paper, the wetting behavior and interface structure of aluminum alloy and T2 copper, Q235 steel, TC4 titanium alloy and TA2 pure titanium are studied, and the contact between the interface reaction and the wettability and the spreading dynamics is discussed. The research contents are expected to further enrich the basic theory of the wettability of the base metal in the hot-dip aluminum technology and the dissimilar metal connecting process. First, the wetting behavior of the molten 6061 and 4043 aluminum alloy on the surface of the T2 copper is studied. The results show that the system is typical of the dissolution and wetting, and the wettability and the temperature are typical in the range of 650-700 oC, and the wettability is gradually improved with the increase of the temperature. The final equilibrium contact angle is about 21 o as the temperature increase wettability is not obviously improved, and the interface layering phenomenon can be explained by the dissolution and precipitation theory, and the whole interface is three layers, and the whole interface is a 2-Al-Cu solid solution, an Al-Cu solid solution and an AlCu intermetallic compound; the content of the molten aluminum alloy in the three-phase line region is relatively small, and the saturation is more easily achieved with the dissolution of the Cu, and the intermetallic compound is precipitated; after the intermetallic compound is generated, the material exchange of the solid-liquid interface of the three-phase line region is prevented, and the droplet spreading is prevented, and the wetting is inhibited; The spreading kinetics of the two systems can be described by the dissolution process control and wetting model,6061 and 4043 aluminum droplets are non-linearly spread on the surface of the substrate, and the wetting activation energy is 52 kJ/ mol and 57 kJ/ mol, respectively. The wetting behavior of molten 6061 and 4043 aluminum alloy on the surface of Q235 steel, TC4 titanium alloy and TA2 pure titanium is studied. The results show that the system is typical of reactive wetting, and the final wettability and temperature are of typical interdependency, and the wettability is improved obviously with the increase of temperature. The micro-Si and Mg in the aluminum alloy lead to the difference of the interface structure and the final wettability, and the Si is rich in the interface, and the thermodynamic condition is satisfied; the Si-rich dense layer (Fe 2 (Al1-xSix)5, Ti7Al5Si12) at the interface blocks the material exchange of the solid-liquid interface of the three-phase line, thereby inhibiting the wetting; Ti7Al5Si12 is unstable, and as the temperature increases, the dense Ti7Al5Si12 is gradually decomposed, and a loose Al3Ti intermetallic compound is generated in the three-phase line region, and the formation of the loose phase can break the oxide film on the surface of the substrate, and promote the reaction between the molten drop of the aluminum alloy and the substrate, thereby promoting the wetting; The Mg is volatilized in the form of steam, and is wrapped in the vicinity of the three-phase line to act as a gas-phase entrainer (reducing agent), and the oxide film on the surface of the substrate is reduced, so that the surface of the substrate is metallic, the molten drop is in contact with the clean substrate and reacts, and simultaneously the three-phase line region produces loose FeAl3 and Al3Ti, the oxidation film on the surface of the substrate can be broken after the loose phase is generated, and the wetting is promoted; the spreading kinetics can be described by a typical reaction product control wetting model; the 6061 aluminum alloy is linearly spread on the surface of the Q235 steel; The surface of the 4043 aluminum alloy in Q235 steel, TC4 titanium alloy and TA2 pure titanium is mainly non-linear spread, and the wetting activation energy can be related to the Gibbs free energy of the interface reaction. Finally, the above-mentioned reaction wetting system has obvious precursor film, the precursor film and the temperature are interdependent, the higher the temperature is, the wider the precursor film is, and at the same time, the appearance of the precursor film is always accompanied by better final wettability, and the forming mechanism is the "Subcutaneous penetration" mechanism.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.44
【引证文献】
相关硕士学位论文 前1条
1 李旭宾;半导体激光与TIG电弧复合热源的熔覆成形机理研究[D];兰州理工大学;2018年
，本文编号：2458897
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