对Ti-6Al-4V合金铸件,先自β相变点以上温度淬火,随后进行970℃(?)750℃循环热处理,能有效地细化铸件的粗大魏氏组织,提高综合机械性能.研究表明,淬火工序可消除晶界α,还可获得全马氏体组织,从而切断了原粗大魏氏组织的遗传性.在随后进行的循环热处理过程中,马氏体分解,β相在α′条的位错及亚结构边界上析出,使原α′条被分割为许多α小晶体,这些小晶体随后聚集长大成位向混乱、互相交织的α针,并随着热循环而发生碎断和球化,成为细碎的网篮组织.
The coarse Widmanstatten structure in Ti-6A1-4V alloy casting can be refined effectively by means of the following heat treatment: quenching from β phase region and then cyclic heating in (α+β) region. The mechanical properties of this casting will also be improved by this treatment. The results show that queching from β phase region can remove the α grain boundaries and thus a whole martensite structure will be obtained. Consequently, the heredity of Widmanstatten structure was cut off. During the subsequent cyclic heating, the martensite decomposes and β phase precipitates on the dislocations and along the substructural boundaries of α′ Plates, so that they are separated into small segments. Accompanying with the increasing number of cycles or time of annealing, the α segments grow up and form acicular α with random orientation. Finally, fine basketwave structure emerges. The breaking of α plates can be well explained by dissolution-separation process caused by cyclic heating.
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