热稳定性
(中南大学 材料科学与工程学院, 长沙 410083)
摘 要: 利用高能球磨法在Fe-Nb-B-Cu体系中获得纳米晶粉末, 研究了机械球磨过程中产物的组织结构、 α-Fe相平均晶粒尺寸及其热稳定性。 结果表明:采用Fe-20B中间合金粉末代替B粉并未明显影响机械合金化动力学过程;磨至5h时, 即可获得平均晶粒尺寸约18nm的α-Fe 球单相过饱和固溶体, 其后延长球磨时间, 晶粒尺寸缓慢减小,至45h后, 平均晶粒尺寸减小到9nm。 退火处理后 的析表明, α-Fe过饱和固溶体从100℃开始发生结XRD分构弛豫现象, 738.8℃后则发生了相转变: α-Fe过饱和固溶体→α-Fe固溶体 + Fe3B + FeB, 在550℃以内退火,晶粒长大不明显,在770~950℃范围内退火, 纳米晶粒开始明显长大, 但晶粒尺寸仍处于纳米级范围。
关键字: 铁基合金; 机械合金化; 纳米晶;热稳定性
(School of Materials Science and Engineering, Central South University,
Changsha 410083, China)
Abstract:Nanocrystalline powder in Fe-Nb-B-Cu system was obtained by high-energy ball milling. The average grain size, thermal stability of α-Fe phase in the powder were studied by XRD, DSC and SEM. The results show that replacing pure boron powder with Fe-20B master alloy does not affect the dynamic process of mechanical alloying. During the course of ball milling, α-Fe supersaturation solid solution, with an average grain size of 18nm, can be obtained after 5h of ball milling. Then with prolonging time of ball milling, grain size decreases slowly. The average grain size gets to 9nm after 45h of ball milling. The α-Fe solid solution undergoes structure relaxation from 100℃, and undergoes phase transformation from 738.8℃. The transition from α-Fe supersaturation solid solution to α-Fe solid solution, Fe3B, and FeB gets the exothermic peak at 803.6℃. Annealing at temperature below 550℃, the nanocrystalline has no significant grain growth. Annealing at the temperature between 770℃ and 950℃, the grain of nanocrystalline grows obviously, but its grain size is still at nanometer range.
Key words: Fe base alloy; mechanical alloying; nanocrystalline; thermal stability