熱穩(wěn)定性
(中南大學(xué) 材料科學(xué)與工程學(xué)院， 長沙 410083)
摘 要: 利用高能球磨法在Fe-Nb-B-Cu體系中獲得納米晶粉末， 研究了機(jī)械球磨過程中產(chǎn)物的組織結(jié)構(gòu)、 α-Fe相平均晶粒尺寸及其熱穩(wěn)定性。 結(jié)果表明：采用Fe-20B中間合金粉末代替B粉并未明顯影響機(jī)械合金化動(dòng)力學(xué)過程；磨至5h時(shí)， 即可獲得平均晶粒尺寸約18nm的α-Fe 球單相過飽和固溶體， 其后延長球磨時(shí)間， 晶粒尺寸緩慢減小，至45h后， 平均晶粒尺寸減小到9nm。 退火處理后 的析表明， α-Fe過飽和固溶體從100℃開始發(fā)生結(jié)XRD分構(gòu)弛豫現(xiàn)象， 738.8℃后則發(fā)生了相轉(zhuǎn)變： α-Fe過飽和固溶體→α-Fe固溶體 + Fe3B + FeB， 在550℃以內(nèi)退火，晶粒長大不明顯，在770~950℃范圍內(nèi)退火， 納米晶粒開始明顯長大， 但晶粒尺寸仍處于納米級范圍。
關(guān)鍵字: 鐵基合金； 機(jī)械合金化； 納米晶；熱穩(wěn)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
