Nb对Zr基块体非晶合金热稳定性、非晶形成能力及机械性能的影响

利用水冷铜模铸造法成功制备了(Zr70Ni10Cu20)90-xNbxAl10(x=0,2,5,7)块体非晶合金,采用XRD,DSC和DTA研究了Nb对该合金体系热稳定性和非晶合金形成能力(GFA)的影响．结果表明,适量Nb的添加可有效提高该合金的GFA和热稳定性．当Nb含量为x=2时,合金具有最宽的过冷液态区(△Tx=119K)和最大的非晶形成能力(参数γ=Tx／(Tg T1)=0．435),Nb的适量添加也有利于提高块体非晶合金的强度和塑性应变,其中x=2的块体非晶的抗压强度和断裂应变量分别达到1783MPa和11．1％。     

Co元素对Ti-Zr-Be-Cu块体非晶合金力学性能的影响

采用铜模铸造法制备了Ti35Zr30Be27.5-xCu7.5Cox(x=0,3.5,7.5,11.5)系列块体非晶合金。采用X射线衍射仪(XRD)、万能试验机和扫描电镜(SEM)研究了Co元素添加对Ti-Zr基非晶合金力学性能的影响。结果表明,Co元素适量替代Be元素有利于提高该非晶合金的塑性。当Co含量(摩尔分数)为3.5%时,Ti35Zr30Be24Cu7.5Co3.5块体非晶合金具有最高的断裂强度及塑性应变,分别为2 196MPa和4%;Co含量为7.5%时,非晶合金断裂强度、塑性应变均迅速降低,分别为2 062 MPa和1.5%;进一步增加Co含量至11.5%时,合金的断裂强度又提高到2 106 MPa,而塑性应变仅为0.2%。     

Co对Ti-Zr-Be-Cu块体非晶形成能力及热稳定性的影响

采用铜型铸造法制备直径为12mm的Ti35Zr30Be27.5-xCu7.5Cox(x=3.5,7.5,11.5)系列块体非晶合金。采用X射线分析(XRD)、差示扫描量热仪(DSC)研究了Co元素含量变化对Ti-Zr基合金的非晶形成能力、结构变化以及热稳定性的影响。结果表明,随着Co元素替代部分Be元素(x=3.5,7.5),合金的非晶形成能力由5mm显著提高到12mm,进一步增加Co元素含量(x=11.5)时,非晶形成能力迅速降低,其形成能力不足5mm;但随着Co含量的变化,Ti35Zr30Be27.5-x Cu7.5Cox(x=3.5,7.5,11.5)系列块体非晶合金的玻璃转变温度Tg、晶化温度Tx分别从x=0时的636K和718K降低到x=11.5时的612K和647K。讨论了Co元素的添加对Ti35Zr30Be27.5-xCu7.5Cox(x=3.5,7.5,11.5)合金结构变化的影响。     

铁元素添加对Cu基非晶合金结构及力学性能的影响

利用铜模吸铸法制备了(Cu_(0.46)Zr_(0.44)Al_(0.08)Dy_(0.02))_(100-x)Fe_x(x=0,1,3,5,7)非晶合金,利用X射线衍射仪(XRD)、同步热分析仪(DSC)、透射电镜(TEM)、万能试验机和扫描电镜(SEM)研究了Fe元素添加对Cu基非晶合金结构及力学性能的影响。结果表明:Fe元素的适量添加有利于改善Cu_(46)Zr_(44)Al_8Dy_2块体非晶合金的结构,当添加原子分数为1%和3%Fe时,合金为完全非晶结构,并且出现富Fe相和富Cu相两相分离。Fe元素的适量添加有利于提高Cu_(46)Zr_(44)Al_8Dy_2合金的强度和塑性,当添加3%Fe时,块体非晶合金的抗压强度σ_f和塑性ε_p分别达到1835 MPa和0.5%。     

Ag和Fe元素添加对Cu-Zr-Al系非晶形成能力和力学性能的影响

以Cu-Zr-Al三元系为基础,研究Ag和Fe合金组元添加对块体金属玻璃(BMG)及BMG基复合材料的非晶形成能力和力学性能的影响.在Cu-Zr-Al三元合金体系中,Cu50Zr42Al8系BMG的△Tx=61 K,Trg=0.624,γ=0.416.适量添加Ag元素能显著地提高非晶形成能力:在Cu-Zr-Al-Ag四元合金体系中,Cu43Zr45Al8Ag4、Cu45Zr42Al8Ag5、Cu40Zr44Al10Ag6、Cu43Zr41Al8A98和Cu36Zr48Al8Ag8的Trg分别为0.618、0.625、0.618、0.628和0.598,γ值分别为0.424、0.427、0.424、0.432和0.433,△TX分别为77、76、78、84和108 K.在(Cu0.36Zr0.48-Al0.08Ag0.08)100-XFex(x-=0,3,5,10,15,20)五元体系中,Fe的添加明显影响合金的非晶形成能力;尽管△TX和Trg呈下降趋势,但(Cu0.36Zr0.48Al0.08Ag0.08)97Fe3块体非晶合金仍具有较高的非晶形成能力,其△TX=103 K,Trg=566,γ=0.424:Fe的适量加入可显著提高合金的力学性能,其中(Cu0.36Zr0.48Al0.08Ag0.08)95Fe5合金的强度和塑性应变分别提高至2 249 MPa和4.9%.Fe元素的存在导致Cu36Zr48Al8Ag8合金中产生明显的相分离,使(Cu0.36Zr0.48Al0.08Ag0.08)100-xFex合金得到增强增韧.     

半固态处理对(Zr_(0.60)Ni_(0.22)Al_(0.18))_(96)Fe_4合金非晶形成能力和力学性能的影响

将Fe元素添加到Zr-Ni-Al合金体系中,采用铜模吸铸法在不同电压下制备出直径为3 mm的(Zr0.60Ni0.22Al0.18)96Fe4圆棒合金试样。采用X射线衍射(XRD),扫描电子显微镜(SEM)、示差扫描量热仪(DSC)、微机控制电子式万能试验机和显微硬度计等设备测试了半固态处理对(Zr0.60Ni0.22Al0.18)96Fe4块体非晶合金的非晶形成能力和力学性能的影响。结果表明,10 kV吸铸的(Zr0.60Ni0.22Al0.18)96Fe4试样为完全非晶结构,合金具有较强的非晶形成能力,其过冷液相区宽度ΔTx可以达到78 K,约化玻璃转变温度Trg(Trg=Tg/Tm)可达0.632;电压8 kV时吸铸制得的(Zr0.60Ni0.22Al0.18)96Fe4合金由非晶主相和少量FeZr2晶体相组成,其断裂强度σf为2 077 MPa,显微硬度为720 HV,塑性应变量εp为1.7%;随吸铸电压适量降低,7 kV吸铸时,合金仍为非晶/晶体复合材料,但晶体相份额增多,合金的强度和硬度提高。     

Zr-Al-Co-Er-Cu系块体非晶合金的形成及其力学性能和腐蚀行为

制备了具有高非晶形成能力的Zr-Al-Co-Er-Cu系非晶块体合金,并研究了Cu元素对Zr-Al-Co-Er块体非晶合金的形成、力学性能和腐蚀行为的影响。研究表明以适量的Cu元素替代Zr-Al-Co-Er合金的Co元素有利于非晶形成能力的提高和力学性能的改善。其中,Zr49Al20Co23Er6Cu2非晶合金的临界直径达6mm,压缩断裂强度达到1950MPa,表现出1.4%的塑性变形。Zr49Al20Co25-xEr6Cux(x=0～8at%)非晶合金在1mol/LH2SO4、3%NaCl(质量分数,下同)溶液中的均发生自钝化,并且具有较低的钝化电流密度。Cu含量的变化对Zr-Al-Co-Er-Cu非晶合金的腐蚀行为没有明显影响。     

Nd对Zr基非晶合金形成能力、热稳定性及耐腐蚀性的影响

利用铜模吸铸法在水冷坩埚中制备了4种(Zr0.55Al0.1Ni0.05Cu0.3)100-xNdx(x=0,1,2,3)块体非晶合金。采用XRD和DSC检测了所获合金相组成、非晶形成能力及热稳定性,并采用盐酸溶液浸泡腐蚀试验评价了不同合金的腐蚀速率。结果表明,适量添加Nd可提高Zr0.55Al0.1Ni0.05Cu0.3非晶合金的形成能力和热稳定性,但非晶合金在2mol/L HCl溶液中的耐蚀性随Nd含量的增加而降低。该结果对进一步改善和提高非晶合金的性能具有重要的参考价值。     

添加微量Fe对Zr_(55)Al_(10)Ni_5Cu_(30)块体金属玻璃非晶形成能力和力学性能的影响(英文)

通过磁悬浮熔炼和铜模吸铸法制备直径3mm的(Zr0.55Al0.10Ni0.05Cu0.30)100-xFex(x=0,1,2,3,4)合金试样,研究Fe元素的微量添加对Zr55Al10Ni5Cu30块体金属玻璃非晶形成能力和力学性能的影响。研究表明,合理添加Fe元素(不超过3%,摩尔分数)导致约化玻璃转变温度Trg(=Tg/Tl)和参数γ(=Tx/(Tg+Tl))增大,因而其非晶形成能力增大,但添加过量的Fe元素(4%)会导致其非晶形成能力的降低。添加Fe元素也会显著地改善Zr55Al10Ni5Cu30块体金属玻璃的压缩塑性及提高其压缩断裂强度,当Fe元素的添加量为2%时,直径3mm、长度6mm的试样在压缩时出现一定的塑性及加工硬化现象。Fe元素添加量为4%形成的金属玻璃基复合材料,同样也显示良好的压缩塑性和高的压缩断裂强度。     

Influence of Minor Addition of In on Corrosion Resistance of Cu-Based Bulk Metallic Glasses in 3.5% NaCl Solution

研究了铜基块体非晶合金Cu55-x Zr37Ti8Inx(x=0～5,at%)及Cu61-x Zr34Ti5Inx(x=0～3,at%)在质量分数3.5%NaCl溶液中的耐蚀性。极化曲线结果表明,在铜基非晶合金中添加In元素能明显提高合金的腐蚀电位、降低腐蚀电流密度,即能明显提高耐蚀性。含In的铜基块体非晶合金的腐蚀电流密度(Icorr)值比不含In的铜基块体非晶合金低约1个数量级。而且,利用In适量取代Cu可进一步提高耐蚀性。但过量添加In不利于形成富Zr保护膜,从而降低合金的耐蚀性。     

Effect of the Compositional Strain on the Diffusive Interface Thickness and on the Phase Transformation in a Phase-Field Model for Binary Alloys

A Cahn-Hilliard phase-field—elasticity model was used to study the effect of compositional strain on the diffusive interface thickness and on the solid state phase transformations in binary alloys. Compositional strain was introduced using the Vegard’s law. Mixed order finite element analyses and analytical solutions of an infinite diffusion couple with a flat interface were used to track the phase-field interface morphology. Both analytical and numerical calculations showed a substantial rate-increasing effect of compositional strain on the interface thickness, especially for low energy barrier values. Compositional strain was found to cause substantial patterning of single precipitates during their evolution in a parent matrix and significantly change the equilibrium size of the precipitates. Results show a considerable influence of compositional strain on the coarsening kinetics of coherent precipitates.     

包含共格畸变的立方合金沉淀机制的计算机模拟

利用包含共格畸变能的微观扩散方程对立方合金的沉淀过程进行计算机模拟。结果表明：共格畸变阻碍了过渡区合金沉淀过程的进行，随共格畸变能的增大，沉淀相分布的取向性越来越明显，由原来离散分布的等轴粒子状向椭片状转变。靠近高浓度合金的过渡区合金，随共格畸变能的增大，其沉淀机制由非经典形核长大和大稳分解的混合特征逐渐向非经典形核长大型的沉淀特征转变。     

含共格畸变的立方合金粗化机制的原子层面计算机模拟研究

基于微观相场动力学模型，编制了包含共格畸变能的二元立方合金沉淀过程微观组织演化的计算机模拟程序，开展了不同共格畸变能作用下，溶质浓度为20at％的二元镍基合金的粗化机制的计算机模拟。研究发现：共格畸变能为零时，粗化遵循LSW机制，仅仅由颗粒的尺寸大小决定：随着共格畸变能的增大，粗化过程遵循混合机制，由沉淀颗粒的大小和位向（颗粒间的相对位置）共同决定；当共格畸变增大到一定程度时，粗化过程纯粹由颗粒间的位向决定，处于弹性“软”方向上的颗粒优先长大，而处于弹性“软”方向外的颗粒将消失掉。     

A simulation study of the shape of β′ precipitates in Mg–Y and Mg–Gd alloys

The metastable β′ phase is a key strengthening precipitate phase in a range of Mg–RE (RE: rare-earth elements) based alloys. The morphology of the β′ precipitates changes from a faceted and nearly equiaxed shape in Mg–Y alloys to a truncated lenticular shape in Mg–Gd alloys. In this work, we study effects of interfacial energy and coherency elastic strain energy on the morphology of β′ precipitates in binary Mg–Y and Mg–Gd alloys using a combination of first-principles calculations and phase-field simulations. Without any free-fitting parameters and using the first-principles calculations, CALPHAD databases and experimental characterizations as model inputs (lattice parameters of the β′ phase, elastic constants and chemical free energy of Mg matrix and interfacial energies of the coherent β′/Mg matrix interfaces), the phase-field simulations predict equilibrium shapes of β′ precipitates of different sizes that agree well with experimental observations. Factors causing the difference in the equilibrium shape of β′-Mg₇Y and β′-Mg₇Gd precipitates are identified, and possible approaches to increase the aspect ratio of the β′ precipitates and thus to enhance the strength of Mg–RE alloys are discussed.     

Simulation of Precipitation Kinetics with Non-Spherical Particles

A kinetic model that is modified based on Langer and Schwartz theory has been developed to treat precipitation kinetics of non-spherical precipitates. Three types of particle morphology, cuboid, needle and plate, have been treated. Explicitly accounting for coherent elastic strain energy and interfacial energy anisotropy, the model enables the prediction of equilibrium particle morphology. The shape effect on growth kinetics has also been investigated assuming quasi steady-state and shape preserving conditions. Validations against a couple of practical examples have shown reasonable agreements, though care must be taken due to uncertainties from model limitations and discrepancies in experimental data.     

Three-dimensional model of precipitation of ordered intermetallics

The development of the two-phase (f.c.c.+L1₂) coherent microstructure in the prototype Ni–Al superalloy is studied by using the three-dimensional computer simulation technique. The dynamics and morphology of the microstructure evolution are described by our three-dimensional version of the stochastic time-dependent kinetic equation which explicitly includes the coherency strain, elastic anisotropy and L1₂ ordering of the preciptate phase. The input parameters, the crystal lattice misfit, elastic moduli, interfacial energy and equilibrium compositions of the coexisting phases are taken from the published independent measurements. The simulation results demonstrate that the strain accommodation in the microstructure evolution results in the cuboidal-like precipitates faceted by the {100} planes. The size of the precipitates obtained in the simulation is of the order of 50 nm. The important conclusion is that the precipitates are always single-domain particles with no antiphase boundaries. This effect is associated with the ordered structure of precipitates. It causes the slowing down of the coarsening kinetics since it excludes the agglomeration of the out-of-phase precipitates in one particle. As has been shown previously, the latter is a very important coarsening mode in an absence of ordering.     

Maraging behavior in an Fe-19.5Ni-5Mn alloy I: Precipitation characteristics

The aging behavior of an Fe-19.5Ni-5Mn alloy has been studied in detail. A substantial maraging-hardening response was obtained upon aging at between 300–550°C, and it displayed classical hardening behavior. The pronounced hardness was attributed to strain hardening caused by coherent, fine spherical precipitates. The activation energy for precipitation, calculated from microhardness data, was 41 kcal/gmole. Ordered fct θ-NiMn precipitates were identified with two different shapes, depending on the aging temperature. Higher aging temperatures resulted in disk-shaped precipitates, while rod precipitates appeared at lower temperatures. Twin-related Widmanstätten austenite grains appeared in a lenticular shape that were coupled together by a twin boundary. Their orientation relationship with the parent martensite was found to be of the Kurdjumov-Sachs (K-S) type.     

共格沉淀析出过程的模拟Ⅱ--外加应力场的影响

采用相场模型对外加应力场对共格沉淀析出过程的微观结构演化进行模拟研究,在外加应力场作用下,非均匀弹性模量系统沉淀相的析出过程发生重大的变化,粒子沿弹性软方向呈各向异性析出,这种各向异性生长与外加应力、点阵错配度的符号以及非均匀模量差的符号有关。采用双级时效模拟方式时,外加应力场对析出相的成核及生长阶段均有影响,只是影响程度与析出相自身的点阵错配度有关。对适当的体系采用应力时效的方式可能是实现除分子束外延技术之外的一种全新的制备超晶格微结构的方法。     

共格沉淀析出过程的模拟Ⅰ--微观结构演化

采用相场模型对共格沉淀析出过程微观结构演化进行模拟研究.模拟结果表明,应力场的存在将会对相变过程中析出相形态产生显著的影响,通过界面能与弹性应变能的相互竞争析出相在不同阶段呈现不同的形态如模量结构、网格结构、三明治多畴结构、沉淀宏观点阵结构以及板条状等;此外,点阵错配度中等(2%～4%)时,粒子的粗化过程将出现应力诱导反向粗化现象,这种粗化现象取决于粒子的点阵错配度与体积分数.     

铁铝黄铜中的Fe_3Al沉淀

在铁铝黄铜的显微组织中观察到3种形貌的Fe_3Al沉淀.通过显微组织发展的研究表明,Fe_3Al的3种形貌反映了其长大过程中的3个阶段.Fe_3Al初析出时和基体共格.粗化过程中,沉淀颗粒沿〈111〉方向生长,于是其形貌发生从立方到树枝状的变化,同时也失去了共格性.