表面自纳米化不锈钢与高强铝合金扩散连接研究
发布时间：2018-10-15 10:32
【摘要】：不锈钢与铝合金在扩散连接过程中,由于物理、化学性能差异较大而使两者的有效连接很难实现,同时连接过程中生成的Fe-Al金属间化合物严重恶化接头的力学性能。因此,本论文采用在扩散连接前对不锈钢和铝合金进行表面自纳米化处理的方式,通过细化材料表面晶粒来达到改善接头综合性能的目的。本论文分别对304不锈钢和7A04铝合金进行表面机械研磨(Surface mechanical attrition technology, SMAT)和超音速微粒轰击(Supersonic fine particles bombarding,SFPB)处理,采用多种试验方法对表面层组织进行表征分析,研究结果表明分别在不锈钢和铝合金表面制备出一定厚度的纳米晶组织。为了确定所制备纳米品组织的热稳定性温度,以制定表面自纳米化304不锈钢与7A04铝合金扩散连接工艺,分别对表面自纳米化304不锈钢和7A04铝合金的纳米组织进行不同温度的等温退火,并采用金相显微镜、X-射线衍射(XRD)、显微硬度仪研究两种金属表层纳米晶组织。最后通过扫描电镜、显微硬度、剪切强度和X-射线衍射分析接头的组织和性能。研究结果表明,经过表面自纳米化处理后,在304不锈钢和固溶时效态7A04铝合金表面分别制备出了厚度为100μm和20μm的纳米晶组织,不锈钢的晶粒细化机制为机械孪晶、位错运动和应变诱发马氏体相变的共同作用,而铝合金的细化机制则是位错运动的结果。表面自纳米化处理在细化晶粒的同时还使材料中的晶界数量和缺陷密度剧烈增加,这将有利于改善扩散连接接头性能。对两种金属表面纳米晶组织热稳定性分析研究表明,304不锈钢纳米晶组织在不高于600℃时具有良好的热稳定性,而7A04铝合金纳米晶组织在不高于500℃时具有一定热稳定性。将表面自纳米化不锈钢和铝合金分别在400℃、425℃、450℃、475℃和500℃的温度下保温0.5h-4h,连接压力设定为6MPa,真空度在1Pa左右,进行真空扩散连接试验,对连接后的试样进行剪切强度的测试,450℃温度连接2h后的剪切强度达到55MPa,剪切强度随着温度的上升和连接时间的延长而先上升再下降。分析不同工艺下接头处的物相组成,生成的金属间化合物为FeAl、AlFe3、Al3Fe和Fe2Al5。综合研究结果,表面自纳米化处理能够有效的提高不锈钢和铝合金在扩散连接过程中原子的扩散系数,降低原子扩散激活能,能够在较低的温度下实现两种材料的有效连接,改善连接接头力学性能。
[Abstract]:In the diffusion bonding process of stainless steel and aluminum alloy, the physical and chemical properties are quite different, which makes the effective bonding between stainless steel and aluminum alloy difficult to be realized. Meanwhile, the mechanical properties of the joints are seriously deteriorated by the Fe-Al intermetallic compounds generated during the bonding process. Therefore, in this paper, the surface self-nanocrystalline treatment of stainless steel and aluminum alloy was carried out before diffusion bonding, and the comprehensive properties of the joints were improved by refining the surface grains of the materials. In this paper, surface mechanical grinding (Surface mechanical attrition technology, SMAT) and supersonic particle bombardment (Supersonic fine particles bombarding,SFPB were applied to 304 stainless steel and 7A04 aluminum alloy respectively. The results show that nanocrystalline structures with a certain thickness are prepared on the surface of stainless steel and aluminum alloy respectively. In order to determine the thermal stability of the microstructure of the prepared nanocrystalline, the diffusion bonding process between surface self-nanocrystalline 304 stainless steel and 7A04 aluminum alloy was established. The nanocrystalline structures of surface self-nanocrystalline 304 stainless steel and 7A04 aluminum alloy were annealed at different temperatures, and the nanocrystalline structures of the two kinds of metals were studied by metallographic microscope and X-ray diffraction (XRD), microhardness analyzer. Finally, the microstructure and properties of the joints were analyzed by SEM, microhardness, shear strength and X-ray diffraction. The results show that nanocrystalline structures with thickness of 100 渭 m and 20 渭 m are prepared on the surface of 304 stainless steel and solution aged 7A04 aluminum alloy after surface self-nanocrystalline treatment. The grain refinement mechanism of stainless steel is mechanical twin. Dislocation motion and strain-induced martensite transformation work together, while the refinement mechanism of aluminum alloy is the result of dislocation movement. The self-nanocrystalline surface treatment not only refines the grain size, but also increases the number of grain boundaries and the density of defects in the material, which will improve the properties of the diffusion bonding joints. The thermal stability of nanocrystalline microstructure on the surface of two kinds of metals was studied. The results show that the nanocrystalline structure of 304 stainless steel has good thermal stability when the temperature is not higher than 600 鈩，
本文编号：2272268
[Abstract]:In the diffusion bonding process of stainless steel and aluminum alloy, the physical and chemical properties are quite different, which makes the effective bonding between stainless steel and aluminum alloy difficult to be realized. Meanwhile, the mechanical properties of the joints are seriously deteriorated by the Fe-Al intermetallic compounds generated during the bonding process. Therefore, in this paper, the surface self-nanocrystalline treatment of stainless steel and aluminum alloy was carried out before diffusion bonding, and the comprehensive properties of the joints were improved by refining the surface grains of the materials. In this paper, surface mechanical grinding (Surface mechanical attrition technology, SMAT) and supersonic particle bombardment (Supersonic fine particles bombarding,SFPB were applied to 304 stainless steel and 7A04 aluminum alloy respectively. The results show that nanocrystalline structures with a certain thickness are prepared on the surface of stainless steel and aluminum alloy respectively. In order to determine the thermal stability of the microstructure of the prepared nanocrystalline, the diffusion bonding process between surface self-nanocrystalline 304 stainless steel and 7A04 aluminum alloy was established. The nanocrystalline structures of surface self-nanocrystalline 304 stainless steel and 7A04 aluminum alloy were annealed at different temperatures, and the nanocrystalline structures of the two kinds of metals were studied by metallographic microscope and X-ray diffraction (XRD), microhardness analyzer. Finally, the microstructure and properties of the joints were analyzed by SEM, microhardness, shear strength and X-ray diffraction. The results show that nanocrystalline structures with thickness of 100 渭 m and 20 渭 m are prepared on the surface of 304 stainless steel and solution aged 7A04 aluminum alloy after surface self-nanocrystalline treatment. The grain refinement mechanism of stainless steel is mechanical twin. Dislocation motion and strain-induced martensite transformation work together, while the refinement mechanism of aluminum alloy is the result of dislocation movement. The self-nanocrystalline surface treatment not only refines the grain size, but also increases the number of grain boundaries and the density of defects in the material, which will improve the properties of the diffusion bonding joints. The thermal stability of nanocrystalline microstructure on the surface of two kinds of metals was studied. The results show that the nanocrystalline structure of 304 stainless steel has good thermal stability when the temperature is not higher than 600 鈩，
本文编号：2272268
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