(北京工業(yè)大學 新型功能材料教育部重點實驗室， 北京 100022)
摘 要: 研究了添加La2O3后鉬的韌性及其韌化機制。 借助于拉伸、 彎曲方法測定了Mo- La2O3材料的斷裂韌性KC和韌-脆轉變溫度(DBTT)， 并用SEM、 TEM、 AES等方法對Mo- La2O3材料的變形、 斷裂特征和組織結構進行了分析。 研究結果表明： 燒結態(tài)Mo-La2O3材料的KC值達到24.76MPa·m1/2， 是純鉬的2.5倍多， 而且高于熱鍛空冷態(tài)TiC-ZrC-Mo鉬合金。 經1900℃退火的Mo- La2O3板， 其韌-脆轉變溫度降低至－60℃， 較同樣狀態(tài)的純鉬板降低了80℃， 故La2O3對鉬具有顯著的韌化效果。 AES結果表明， 添加La2O3并不改變C、 N、 O等致脆雜質在鉬晶界上的分布狀態(tài)。 Mo- La2O3材料的韌化主要歸因于其抗裂紋擴展能力的提高， 而這與La2O3粒子改變鉬中的位錯分布及組態(tài)有關。 并提出了一種新的韌化機制—硬脆第二相的韌化機制， 能很好解釋實驗結果。
關鍵字: 鉬；La2O3； 斷裂韌性； DBTT； 第二相韌化
（The Key Laboratory of Advanced Functional Materials of Ministry of Education,
Beijing Polytechnic University, Beijing 100022, China）
Abstract: The KC and DBTT of both sintered and recrystallized Mo alloy doped with La2O3 (Mo- La2O3) as well as unalloyed molybdenum were tested and the microstructure was investigated by SEM, TEM and AES. The results show that the KC of Mo- La2O3 alloy reaches to 24.76MPa·m1/2, which is 2.5 times as much as that unalloyed Mo. The DBTT of Mo- La2O3 sheet annealed at 1900℃ for 60min is decreased to -60℃, which is 80℃ lower than that of unalloyed Mo. The Mo- La2O3 alloy has similar equiaxed grain structure with the unalloyed Mo. The AES analysis revealed that the same content of interstitial impurities exist on grain boundaries of Mo- La2O3 and unalloyed Mo. A toughening mechanism was proposed to be that large number of dislocations were pinned around La2O3 particles, shorting the efficient slip length and decreasing the dislocations pile-up on grain boundaries of Mo. The toughness improvement of Mo- La2O3 alloy was attributed to the relax of stress concentration at grain boundaries of Mo- La2O3 alloy and the weaker tendency to intergranular fracture on grain boundaries.
Key words: molybdenum; La2O3; fracture toughness; DBTT; second phase toughening
