Kim Byungchul, Jang Jinsung, Kim Tae Kyu, Ahn Jung-Ho
School of Material Engineering, Andong National University, 388 Songchun-dong, Andong, Gyungbuk 760-010, South Korea.
J Nanosci Nanotechnol. 2012 Jul;12(7):5510-3. doi: 10.1166/jnn.2012.6319.
In the present work, the evolution of nanoparticles during annealing and hot-consolidation in mechanically alloyed Ni-22Cr-1.5Y, Ni-22Cr-1.5Y2O3 and Ni-3% Y2O3 was examined. The high-energy ball-milling of elemental powders resulted in the complete dissolution of the constituent Cr, Y, or Y2O3, forming a Ni-based solid solution. During the subsequent annealing, however, oxide particles precipitated from the solid solution. In the case of mechanically alloyed Ni-22Cr-1.5Y2O3, over-grown Cr2O3 precipitated at a temperature as low as above approximately 500 degrees C and ternary YCrO3 particles precipitated at 1100 degrees C. In the case of mechanically alloyed Ni-22Cr-1.5Y, on the other hand, the binary Y2O3 phase precipitated at 1100 degrees C during spark plasma sintering. The presence of Cr in the alloy composition facilitated the formation of Cr2O3 or YCrO3, and the precipitated oxides were highly prone to grain growth during hot-consolidation, sometimes reaching several micrometers. In Cr-exempt Ni-3%Y or Ni-3% Y2O3, however, the growth of nanodispersoids was restrained even at temperatures as high as 1000 degrees C and the resulting dispersoid was only nano-sized Y2O3.
在本研究中，对机械合金化的Ni-22Cr-1.5Y、Ni-22Cr-1.5Y2O3和Ni-3%Y2O3在退火和热固结过程中纳米颗粒的演变进行了研究。元素粉末的高能球磨导致成分Cr、Y或Y2O3完全溶解，形成镍基固溶体。然而，在随后的退火过程中，氧化物颗粒从固溶体中析出。对于机械合金化的Ni-22Cr-1.5Y2O3，在低至约500℃以上的温度下会析出过度生长的Cr2O3，在1100℃时会析出三元YCrO3颗粒。另一方面，对于机械合金化的Ni-22Cr-1.5Y，在放电等离子烧结过程中，二元Y2O3相在1100℃时析出。合金成分中Cr的存在促进了Cr2O3或YCrO3的形成，并且析出的氧化物在热固结过程中极易发生晶粒生长，有时可达几微米。然而，在不含Cr的Ni-3%Y或Ni-3%Y2O3中，即使在高达1000℃的温度下，纳米弥散相的生长也受到抑制，最终得到的弥散相仅是纳米尺寸的Y2O3。
