【摘要】 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。更多还原

【Abstract】 In this paper,the morphology and behaviour of grain boundary migration at theweld interface in diffusion welding of titanium and its alloys have been investigated bymeans of high temperature microscopy.The authors find that morphology of β-grainboundary is in close relationship with the state of weld interface prior to phase transfor-mation.In the test pieaes which have not been subjected to pressure prior to phasetransformation,a lot of β-grain boundaries perpendicular to the interface will occur asthe temperature rises above the phase transformation point.And in the test pieces whichhave been subjected to pressure for a period of time before phase transformation,grainboundary will cross the interface as soon as it occurs.The migration of the triplepoint away from the interface and its displacement parallel to the weld interface werethe dominant forms of grain boundary motion.The change of energy of the interfacewas the main driving force of grain boundary migration.Crossing of boundary overthe interface will easily occur in the weld interface locally deformed.Therefore,excel-lent diffusion welds can be obtained by the welding procedure in which test pieces arepressed at a temperature below the phase transformation point and then kept at a tem-perature above the phase transformation point for a period of time.更多还原