【作者】 王毅；

【导师】 周琦； 余进；

【作者基本信息】 南京理工大学 ， 材料工程（专业学位）， 2018， 硕士

【摘要】 钛合金铝合金作为航空航天领域主要用材,对于二者的结合使用对工业与科学技术发展有着重要意义,然而因为钛合金与铝合金的物理、化学性能有着较大差异,导致了二者的连接存在接头强度不高的问题。本文就接头强度提升方面提出了优化方法。熔钎焊接是钛铝异种金属连接的常规方法,其通过控制金属间化合物的方式能够获得较好的钛铝连接接头。本文基于熔钎焊接工艺提出了一种微区重构的连接强化工艺。该工艺利用钛合金与铝合金的高熔点差,通过在高熔点区域进行束流扫描,经固态传热达到接头微区重熔目的。实验结果表明这种接头连接强化工艺对钛铝焊缝金属间化合物层能够进行重熔改性,钛铝金属间化合物层的元素分布以及界面形态发生了改变,铝镁合金与TA2钛的异种连接接头拉伸强度可达165MPa,达到铝镁合金母材强度的75%,对比文中熔钎焊工艺得到的接头强度126MPa有了较为明显的提升。并且将该接头连接强度优化工艺应用至TC4钛合金与6061铝合金异种金属连接中,得到接头强度达184MPa,为6061铝合金母材强度的71%。将该优化工艺与搭接接头设计的钛合金铝合金异种金属连接配合,得到了接头力学性能表现优异,接头强度达196MPa,为铝母材强度的75.4%。文中对钛铝的熔钎焊连接接头界面以及使用接头强度优化工艺连接的接头界面分别进行了微观组织分析、XRD物相分析与EDS分析,XRD结果显示了接头物相有Ti3Al、Ti2Al、Ti5Al11、TiAl2、TiAl和TiAl3。文中还通过钛铝二元体系的Miedema模型,对界面各金属间化合物的生成焓进行了计算,同时对各金属间化合物的吉布斯自由能进行了计算分析,综合各分析结果,推测得到接头中的金属间化合物主要有Ti3Al、TiAl和TiAl3。线扫描成分分析结果显示了钛铝结合面处铝向钛扩散距离较钛向铝扩散距离要小的多,重熔后得到的接头钛铝金属间化合物层宽度约6微米。文中对接头力学性能表征结果显示了钛铝熔钎焊接头断口为明显脆断,且断面成分分析显示了断面处存在近似1:1的钛元素与铝元素;接头强度优化工艺后的接头断面存在较多位置出现韧窝,且韧窝处成分显示为>97%的铝元素。综以上分析结果,接头强度优化工艺对接头拉伸力学性能以及接头韧性都起到了一定的改善效果。更多还原

【Abstract】 The industrial area has asked for higher quality requirements on the functional materia with the development of science and technology.But the connection strength between titanium alloy and aluminum alloy is always deficiency for its service in the aerospace area because of the physical and chemical difference between the two elements.In this paper an optimization of the process is put forward for the better joint of titanium alloy and aluminum alloy.Welding brazing is the normal way to connect titanium alloy and aluminum alloy and this process could get the two alloy connected with the joint strength no better than 70%of basic materia.In this paper micro area remelting at the interface is added to the welding brazing process in order to heat the titanium alloy side and melt the intermetallic compound layer.The remelting process resulted in the transformation of microstructure、size and constituent of the intermetallic compound layer.In this paper the joint of titanium alloy and aluminum alloy connection tensile strength could be 165MPa which is 75%of the basic aluminum alloy 5052 tensile strength.The connection strength between TC4 and 6061 aluminum could be 184MPa which is 71%of the basic aluminum alloy 6061 tensile strength.In this paper OM、SEM、EDS and XRD are used to help research the microstructure distribution,elements distribution and the phase composition.Results of the reaserch showed that the morphology of intermetallic compound layer has an obvious transformation happened after the remelting process.From XRD’s results the intermetalic compound Ti3Al、Ti2Al、TiA12、Ti5Al11、TiAl and TiAl3 are found.The main change is caused by the intermetallic compound TiAl3’s decrease.The stretch fracture morphology of samples with the remelting process showedbetter toughness than the ones without remelting process.The element on the stretch fracture surface of the samples with the remelting process is mainly Al element.Also the calculation of the chemical energy is contained in this paper for the theory analysis and results show the intermetallic compound tends to be the TiAl.Also analysis on the topography of fracture surface indicated the remelting process had a toughing effect on the joint between titanium and aluminum.更多还原