周宏明
,
易丹青
,
柳公器
,
肖来荣
稀有金属材料与工程
采用X射线衍射(XRD)、扫描电子显微镜(SEM)、维氏硬度计、电子万能材料试验机研究MoSi_2-Si_3N_(4(p))/SiC_(w)复合材料的结构、形貌、硬度、断裂韧性,并对SiC晶须和Si_3N_4颗粒复合强韧化MoSi_2的机理进行了探讨.结果表明,SiC晶须和Si_3N_4颗粒对MoSi_2具有协同强韧化作用,MoSi_2-20%Si_3N_(4(p))-20%SiC_(w)(体积分数,下同)复合材料的抗弯强度达427 MPa,室温断裂韧性达到10.4 MPa·m~(1/2),均高于单一强韧化剂的强韧化效果.MoSi_2-20%Si_3N_(4(p))-20%SiC_(w)复合材料的强化机理为细晶强化和弥散强化;韧化机制为细晶韧化、裂纹偏转与分支和微桥接韧化.
关键词:
MoSi_2
,
复合材料
,
Si_3N_4颗粒
,
SiC晶须
,
强韧化机制
杜伟
,
张来启
材料科学与工程学报
采用第一原理方法,计算了MoSi_2及其三元合金(Mo,M)Si_2(M=Nb、Tc、Ta、W)的电子结构,表面能(γ_s),不稳定层错能(γ_(us)),以及弹性常数.从"韧化参数"D-γ_s/γ_(us)以及弹性性质两个方面研究了合金化对MoSi_2韧性的影响.研究表明,MoSi_2(001)Si-|-Si具有较低的表面能,是最可能的解理面;带有方向性的强Mo4d-Si3p共价键是MoSi_2本征脆性的最主要原因.Nb、Tc、Ta合金化有利于增强MoSi_2的韧性;W则起到增脆作用.合金增韧的主要原因是弱M4d-Si3p键代替了方向性的强Mo4d-Si3p键.
关键词:
MoSi_2
,
本征脆性
,
合金化
,
第一原理
张小立
,
金志浩
,
张振国
,
王志新
复合材料学报
研究了低成本制备技术反应熔渗方法制备的SiC/MoSi_2和SiC/Mo(Si,Al)_2复合材料高温氧化行为.表面氧化物的形态和氧化增重的研究结果表明,所制备复合材料高温氧化3 h后即发生钝化现象,继续在500℃再进行低温氧化试验,发现限制该材料使用的"Pest"现象消失.其中渗铝复合材料SiC/Mo(Si,Al)_2高温增重较渗硅SiC/MoSi_2严重.当后者中形成的SiC增强相全部为原位反应生成时,由于界面结合力提高,抗氧化能力更强.
关键词:
反应熔渗
,
MoSi_2
,
复合材料
,
抗氧化行为
,
Pest
R.Gibala H.Chang C.M.Czarnik K.M.Edwards A.Misra Department of Materials Science and Engineering
,
University of Michigan
,
Ann Arbor
,
Michigan 48109-2136
,
USA
材料科学技术（英文）
This paper demonstrates that plasticity enhancement processes previously observed in bcc metals and associated with the presence of surface films and precipitates or dispersoids are operative in or- dered intermetallic compounds.' Some specific results are given for NiAl-and MoSi_2-based materials.The plasticity of NiAl and related B2 ordered alloys at room temperature during monotonic deformation can be enhanced by application of surface films such as electroless nickel platings.Sig- nificant effects are also observed during cyclic deformation.The presence of ductile second phases such as fcc γ or the ordered phase γ' introduced by alloying also enhances the plasticity of NiAl. MoSi_2 exhibits similar effects of surface films and second phases,but primarily at elevated tempera- tures,T>900℃.In this paper,we illustrate the effects of ZrO_2 surface films deposited near room temperature and TiC particulate additions introduced by powder processing techniques.In all cases, the plasticity enhancement is associated with enhanced dislocation generation processes under the conditions of constrained deformation at the film-substrate or precipitate/dispersoid-matrix inter- face of the composite system.
关键词:
plasticity
,
null
,
null
,
null
ZHENG Lingyi
,
JIN Yanping
,
LI Pengxing(The State Key Laboratory of Metal Matrix Composites Materials
,
Shanghai Jiao Tong University
,
Shanghai 200030
,
China)
金属学报(英文版)
MoSi_2 and 30 vol.% SiC_p/MoSi_2 composite have been fabricated by hot pressing (HP).A simulated thermal cycle experiment has been carried out at 1100℃ for 32 h to investigate the stability of the composite system.Comparative,mechanical tests,including measurement of flexural strength and fracture toughness at room temperature,have been conducted between materials before and after thermal cycle.It is shown that both the strength and fracture toughness are enhanced by the addition of SiC particles. After thermal cycle,the strength of both materials increases and the toughness decreases by about 20%.The result that the composite system is not corroded intensely by thermal cycle shows that SiC particles are feasible reinforcement for MoSi2.
关键词:
:thermal cycle
,
null
,
null
,
null
,
null
席俊杰
材料导报
比较了MoSi_2发热元件的热弯成形和挤压成形工艺方法,指出热弯成形更易获得大型尺寸和复杂形状发热元件,研究了MoSi_2发热元件的技术进展及其工业应用.研究表明,改进MoSi_2粉体的制备工艺、MoSi_2发热元件的成形工艺和冷热端的扩散接合工艺是MoSi_2发热元件改性的技术关键.提出了其未来研究发展的方向.
关键词:
MoSi_2发热元件
,
自蔓延高温合成
,
热弯成形
