Microstructure evolution of nanostructured Ni3Al during annealing

A nanocrystalline layer was produced on the surface of Ni3Al intermetallic by means of surface mechanical attrition treatment. The surface nanocrystallites were annealed at 250-750 ℃ for 30 min. Microstructure evolution of nanocrystallites during annealing was studied by X-ray diffraction （XRD） and transmission electronic microscope （TEM）. The experimental results show that long-rang order recovers rapidly when annealing temperature is below 250℃ and changes slowly at 350-550 ℃, and then it increases rapidly at 750℃. The grain size of nanocrystallites of Ni3Al keeps stable and crystal defects recover when they are annealed below 550℃. The grains grow normally in low temperature annealing and abnormal growth occurs at 750℃.     

L12结构Ni74.5Pd2Al23.5合金的反相畴界能

应用TEM弱束技术，测得Ll2结构的Ni74.5Pd2Al23.5合金（111）和（100）面的反相畴界APB能分别为（144±20）mJ／m2和（102±11）mJ／m2．实验数据与Ni3Al的APB能数据接近因此，Ni74．5Pd2Al23．5合金塑性的提高与合金APB能的大小无明显关系     

硼与Ni3Al的再结晶

对无硼，含硼５００ｗｐｐｍ和含硼２００ｗｐｐｍ的多晶Ｎｉ３Ａｌ在７００～１０００℃范围内的再结晶和晶粒长大过程进行了研究，其中无硼和部分含硼５００ｗｐｐｍ和含硼２０００ｗｐｐｍ的合金分别经受了２０％和４０％的冷轧加工，研究中没有观察到明显可见的硼对再结晶和晶粒长大动力学的影响，上述材料的再结晶过程都遵循ＫＪＭＡ关系，并且都具有接近于１的Ａｖｒａｍｉ指数。晶粒长大过程都遵循指数关系。其时间常数均小于     

Fe3Al基合金超塑性变形过程中位错结构的演化

利用ＴＥＭ研究了Ｆｅ３Ａｌ基合金超塑性变形过程中位错结构的变化。发现变形后晶内位错密度显著降低，且试样变形部位与部的位错结构及密度有较大差异。位错滑动在Ｆｅ３Ａｌ超塑性变形中起重要作用。     

K465高温合金铝化物涂层Ni/Al互扩散系数计算

根据铝化物涂层形成过程中Al原子浓度分布，采用有限差分法反求铝化物外层Ni／Al互扩散系数．结果表明：相同温度下，铝化物外层Ni／Al互扩散系数随Al原子浓度增加而增大，表现出与Al浓度相关性；合金表面渗铝外层Ni／Al互扩散系数明显小于纯Ni表面渗铝外层Ni／Al互扩散系数．     

三种M3Al型金属间化合物的低温热腐蚀

Na_2SO_4沉积物显著地加速Fe_3Al、Ni_3Al和Ti_3Al在600℃模拟燃气气氛中的腐蚀.腐蚀产物为M与Al的氧化物和硫化物的混合物.Fe_3Al和Ti_3Al的耐蚀性优于Ni_3Al因为Fe_3Al腐蚀产物中有一含高Al_2O_3的内层在Ti_3Al上则有由TiO_2和NbO_2组成的中间层而Ni_3Al的腐蚀产物的内层含有大量硫化镍有利于Ni的向外传输Na_2SO_4中添加NaCl对三种M_3Al的腐蚀过程无明显影响     

Pd韧化Ni3Al的微观机制

在对含Ｐｄ的Ｎｉ３Ａｌ合金进行成键特征分析基础上，用已建立的理论模型解释了Ｐｂ韧化Ｎｉ３Ａｌ的微观机制。Ｐｄ在Ｎｉ３Ａｌ中占据Ｎｉ原子位置，其成键电子的离域程度远大于Ｎｉ原子，可有效地削弱共价键的方向性而强化晶界结合力，改善多晶Ｎｉ３Ａｌ的韧性。偏离化学计量比对Ｐｄ韧化Ｎｉ３Ａｌ效果的影响，是因为Ｐｄ－Ｎｉ键较Ｐｄ－Ｎｉ键强。降低Ａｌ含量可增加离域的成键电子数，有利于Ｎｉ３Ａｌ的韧化。     

MOLECULAR STATIC SIMULATION OF ENERGY FEATURESOF INTERACTION BETWEEN GRAIN BOUNDARYAND DISLOCATIONS IN Ni＿3Al ALLOY

ＭＯＬＥＣＵＬＡＲＳＴＡＴＩＣＳＩＭＵＬＡＴＩＯＮＯＦＥＮＥＲＧＹＦＥＡＴＵＲＥＳＯＦＩＮＴＥＲＡＣＴＩＯＮＢＥＴＷＥＥＮＧＲＡＩＮＢＯＵＮＤＡＲＹＡＮＤＤＩＳＬＯＣＡＴＩＯＮＳＩＮＮｉ＿３ＡｌＡＬＬＯＹＣｈｅｎ，Ｄａ；Ｌｕ，Ｍｉｎ；Ｌｉｎ，Ｄｏｎｇ...     

Ni3Al晶界结构的计算机模拟

本文运用嵌入原子法势函数和静态弛豫最陡梯度的计算方法,模拟[100],[110]和[111]轴一系列具有不同晶界几何参量及化学成分的Ni_3Al对称倾侧晶界原子结构、晶界能和晶界的内聚能、电荷密度分布及应力场等内容,并着重研究和讨论了它们与硼偏聚,Ni_3Al的晶界韧脆行为,特别是硼韧化的化学计量效应之间的关系。     

COMPUTER SIMULATION OF GRAIN BOUNDARY STRUCTURES IN Ni_3Al

The embedded atom type potentials and static relaxation method combined with steepest gra-dient computational technique have been used to simulate the grain boundary cohesive ener-gies,the distribution of electron density and stress field in the grain boundary,region,and oth-er related problems of[100],[110]and[111]symmetric tilt grain boundaries in Ni_3Al withdifferent grain boundary geometrical index and composition.Their relations with the segrega-tion or boron,behaviors or the grain boundary,and especially the stoichiometrical effect of Binduced ductility have also been studied and discussed.     

SIMULATIVE INVESTIGATION OF GRAIN BOUNDARIES IN NiAl ALLOY

１ＩＮＴＲＯＤＵＣＴＩＯＮＮｉＡｌａｌｏｙｗｉｔｈａＢ２ｓｔｒｕｃｔｕｒｅｈａｓａｈｉｇｈｍｅｌｔｐｏｉｎｔ（１６３８℃），ｌｏｗｄｅｎｓｉｔｙ（５．８６ｇ／ｃｍ３），ｈｉｇｈｍｏｄｕｌｅ（２９４ＧＰａ）ａｎｄｈｉｇｈｈｅａｔｃｏｎｄｕｃｔｉｏｎｃｏ...     

Zr对Ni3Al晶界及力学性能的影响

对不同Ｚｒ含量Ｎｉ３Ａｌ的力学性能及晶界的研究结果表明：随Ｚｒ含量的增加，合金的屈服强度和抗张强度不断提高；当Ｚｒ≤０．７ａｔ．－％时，塑性随Ｚｒ含量的增加而提高；但Ｚｒ含量达１．２ａｔ．－％时，Ｚｒ的增塑效果下降．Ａｕｇｅｒ能谱分析表明：Ｚｒ在晶界有偏聚，偏聚因子约为３．断口观察显示：不含Ｚｒ或Ｚｒ含量为１．２ａｔ．－％的Ｎｉ－２４．０Ａｌ合金均为沿晶断裂，其余含Ｚｒ合金的断裂方式为穿晶、沿晶混合断裂．这表明：含Ｚｒ的Ｎｉ３Ａｌ塑性和Ｚｒ在晶界的偏聚有密切关系．     

LOCAL CHEMISTRY AND THE COHESIVE STRENGTH OF GRAIN BOUNDARIES IN Ni_3Al

ＬＯＣＡＬＣＨＥＭＩＳＴＲＹＡＮＤＴＨＥＣＯＨＥＳＩＶＥＳＴＲＥＮＧＴＨＯＦＧＲＡＩＮＢＯＵＮＤＡＲＩＥＳＩＮＮｉ_３ＡｌＳｈａｎｔｈｉＳｕｂｒａｍａｎｉａｎ；ＤａｖｉｄＭｕｌｌｅｒ；ＪｏｈｎＳｉｌｃｏｘａｎｄＳｔｅｐｈｅｎＬ．Ｓａｓｓ（Ｄｅｐａｒｔ?..     

Mg的晶界偏聚效应及其对Ni_3Al(0.1B)抗腐蚀性能的影响

在金属间化合物Ni_3Al(0.1B)中注入能量为120keV,剂量为1×10~(16)ion/cm~2的Mg~+离子用多次扫描循环极化曲线测量和光学显微镜观察研究其腐蚀行为.发现经Mg~(+)离子注入后的样品在0.5mol/L H_2SO_4溶液中的抗蚀性能有很大的改善对Mg原子的偏聚现象进行实验测试和计算机模拟,增进了对Mg~(+)离子注入提高金属间化合物抗蚀性能机制的了解     

SLIP FEATURE AND GRAIN BOUNDARY BEHAVIOURS OF Ni_3Al ALLOYS DURING DEFORMATION

The deformation behaviours of Ni_3Al alloys with various chemical compositions and subjectedto different heat treatments were in situ observed under SEM. Moreover,in situ observationsof slip trace were supplemented by the direct observation of dislocation arrangements underTEM.In B-doped Ni_3Al alloys it is shown that close to the grain boundary there exists a thinslip transition region,within which slip lines are reoriented or other slip systems are operatedto produce a local strain accommodation and to relax the stress concentration at grain bound-aries.Boron seems to lower the stress for dislocation generation from the grain boundaries orto ease the cross-slip close to the boundaries,and also to increase the number of dislocationsources.However,B-enhenced ductility is seriously affected by stoichiometry,the addition ofa tertiary alloy element and heat treatment,etc..     

Ni3Al合金的滑移特征及形变过程的晶界行为

通过SEM动态拉伸形变试验,研究了具有各种化学成分和不同热处理态Ni_3Al合金的形变滑移特征,并用TEM观察了晶界区域的位错组态。研究结果表明,在含硼Ni_3Al合金的晶界附近存在一个过渡滑移区,该区域中滑移线重新取向或其它滑移系开动,从而产生了局部应变调节并使晶界应力集中松弛。硼降低了开动晶界位错源所需的应力并可能同时增加了位错源本身的数目。硼对Ni_3Al的韧化作用强烈受到基体Al含量、合金元素及热处理等因素的影响。     

在Ni_3Al中硼的非平衡晶界偏聚

在１０２３～１３７３Ｋ的初始温度范围和０．０５～２６８．９１Ｋ／ｓ的冷速范围内，用俄歇剖层分析确定了含硼Ｎｉ_３Ａｌ合金中硼的非平衡晶界偏聚行为。基于由空位在晶界湮灭所产生的体系自由能下降驱动可动的溶质－空位复合体向晶界迁移、从而产生溶质非平衡晶界偏聚的模型，导出了定量描述非平衡偏聚行为的解析表达式。理论计算结果与硼非平衡偏聚的试验数据相符。通过模拟实测确定Ｎｉ_３Ａｌ－Ｂ合金中硼及硼－空位复合体的扩散系数分别为：Ｄ＝１×１０￣（－６）ｅｘｐ［－１．９６（ｅＶ）／ｋＴ］和Ｄ_（Ｐ（Ｂ））＝１×１０￣（－）４ｅｘｐ［－１．９６（ｅＶ）／ｋＴ］（ｍ￣２／ｓ）；硼－空位复合体的结合能为Ｅ_（ｂ（Ｂ）＝０．５ｅＶ。