采用透射电镜,X射线衍射和硬度测量等方法研究了Ni-Fe-Nb-Al合金调幅结构的形成和生长,认为是典型的调幅结构。 合金中Al原子的加入,加速了合金调幅结构的生长。在早期时效阶段,γ′[Ni_3(Al,Nb)]预沉淀相沿〈100〉三个方向周期的排列。在[001]和[011]晶带衍射条件下,显微象呈平行条纹,其条纹间隔为100A。随着时效的延长,显微象呈现出花呢结构。更进一步时效,平行条纹间距增大一倍为200A。合金在550,700和800℃三种温度下,时效10h后,γ′沉淀相在调幅结构的条纹上析出,颗粒沿[100]和[010]两方向规则排列。 在各种时效制度下,合金的X射线衍射圈(220)主峰旁均出现一侧边峰。 根据调幅结构的生长过程与合金硬度的变化规律,探讨了Ni-Fe-Nb-Al合金在时效过程中硬化的本质.解释了Ni-Fe-Nb-Al合金比Ni-Fe-Nb合金硬度高的原因。
The formation and growth process of modulated structure in a NiFeNbAlalloy during aging have been investigated by means of TEM, X-ray diffraction andhardness measurements. The presence of Al in the alloy appears to accelerate thegrowth process of the structure. At an early stage of aging, the pre-precipitatesof γ′[Ni_3(Al,Nb)] phase in the alloy has been found to arrange in line along thethree <100> directions; and a micrograph showing parallel striations has also beenobtained under [001] and [011] zones of the electron diffraction. At this stagethe spacing of the striations was about 100A. When the aging period was pro-longed a "tweed structure" appeared. Further increase of aging time widened thespacing of parallel striations to about 200A. With 10h-aging at 550, 700 or 800℃,γ′ particles were observed at the striations of the modulated structure in the alloyand appeared to be in perfect arrangement along [100] and [010] directions. X-raydiffraction of the alloy showed that there is a side-band on the (220) main peakunder various aging conditions. Attempts have also been made to clarify the natureof hardening of the alloy during aging as well as to explain the higher hardnessin NiFeNbAl alloy than in NiFeNb alloy.
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