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本文通过高温金相观察,对铁及钛合金扩散焊接过程中接合区的晶界形态及其迁移行为进行了试验研究。试验发现,接合区的β晶体形态与相变前界面的状态密切相关。相变前未经加压的试样,当升温到相变点以上时,界面区出现较多的垂直于界面的β晶界,而相变前已加压一段时间的试样,则β晶界一开始显现即可越过界面。同时观察到三晶结点远离界面的迁移以及平行于焊接界面的移动是接合区晶界迁移的主要形式,而界面能的变化则是晶界迁移的主要动力。界面孔洞对于晶界迁移具有钉扎作用,而经过一定局部变形的界面,则易于发生越过界面的晶界迁移。为此,作者提出采用在相变点温度以下加压,然后再升温到相变点之上保温的焊接工艺循环,可以有利于获得优质焊接接头。
In this paper, through high-temperature metallographic observation, the grain boundary morphology and migration behavior of the bonding zone during the diffusion welding of iron and titanium alloys were studied. It is found that the β crystal morphology in the bonding region is closely related to the state of the interface before the phase transition. When the sample was not pressurized before the transformation, when the temperature was raised to above the transformation point, the interface area appeared more perpendicular to the interface of the β grain boundaries, and the phase transition has been pressurized for a period of time before the sample, the β crystal Boundaries can be crossed as soon as they appear. At the same time, it is observed that the migration of the triple junction away from the interface and the parallel movement to the welding interface are the main forms of the grain boundary migration in the bonding zone. The change of the interface energy is the main driving force for the grain boundary migration. The interface hole has a pinning effect on the grain boundary migration, and after a certain local deformation of the interface, it is easy to occur across the interface grain boundary migration. To this end, the authors propose that a welding process cycle that applies pressure below the transformation temperature and then heats it up to the point of transformation allows for a good welded joint.