置氢烧结Ti-6Al-4V合金的显微组织演变规律

Microstructure evolution mechanism of hydrogenated sintering Ti-6Al-4V alloy

通过在原料粉末中配置TiH_2粉末的方法将烧结Ti-6Al-4V合金的实际置氢量控制在0~0.69%,系统研究了置氢量对显微组织演变、相构成、形态与分布的影响规律,并借助OM、SEM、EDS、XRD和EBSD开展探究与表征。结果表明:1)置入0.12%的氢可以使合金获得近平衡态显微组织的烧结时间从3 h减少为2 h。2)当置氢量逐步增加到0.69%时,α相含量从82.44%急剧减少至15.22%,而β相含量从3.59%增加到50.77%,同时α相的形态从粗大片状转变为断续分布于β相周围的细片状,β相的形态则从断续分布于α相间的细条状转变为板块状。3)随着置氢量的提高,HCPα'马氏体的含量从8%左右增加到约25%,并呈局部集中状分布在α相内;置氢量为0.54%时,针状δ氢化物开始生成,分布在α和β相内及两相之间,此时α'的含量再次降低至8%左右。4)斜方结构马氏体α"的含量也随着置氢量的提高而增加,但是当α"含量达到5%左右后便维持不变,呈细小等轴状分布于α相内。5)置氢量对合金中显微组织构成、α+β片层束及晶粒形态能够产生显著影响。最后,根据实验结果对置氢烧结Ti-6Al-4V合金显微组织的演变机理开展了分析与讨论。

The real hydrogenation contents were controlled in the range from 0 to 0.69%（mass fraction） by adding Ti H2 powders to the raw powders, and the effects of real hydrogenation contents on microstructure evolution and phase composition, morphology and distribution of sintering Ti-6 Al-4 V alloys were comprehensively investigated. Means of OM, SEM, EDS, XRD and EBSD were used for the exploration and characterization. The results are as the follows： 1） The time for microstructure reaching the near-equilibrium-state reduces from 3 h to 2 h at hydrogenation content of 0.12%. 2） With hydrogenation content increases to 0.69% gradually, the volume fraction of α phase reduces from 82.44% to 15.22% and the volume fraction of β phase increases from 3.59% to 50.77%. Meanwhile, coarse lamellar α phase transforms to fine lamellar α phase distributing around β phase discontinuously, and thin strip β phase distributing between α phases discontinuously transforms to plate β phase. 3） The volume fraction of HCP α′ martensite increases from about 8% to about 25% with the increase of hydrogenation content, which distributes in α phase locally and intensively; Acicular δ hydride generates at 0.54% hydrogenation content, which distributes in α and β phases and between the two phases. Meanwhile, the volume fraction of HCP α＇ martensite reduces to about 8% again. 4） Though the volume fraction of orthorhombic α＂ martensite increases with the increase of hydrogenation content, it only reaches about 5% and distributes in α phase with small equiaxed shape. 5） The hydrogenation content can also effectively affect the microstructure composition,（α＋β） lamellar beam and grain morphology. Finally, the microstructure evolution mechanism of hydrogenated sintering Ti-6 Al-4 V alloys was analyzed and discussed on the basis of experimental results.