Effect of Zr, Mo and Y Adding on Microstructure, Mechanical and Electrical Properties of Au-Pd, Pt-Ir and Pd-Ru Systems

在Au-Pd、Pt-Ir、Pd-Ru系中分别加入Zr、Mo、Y 3种元素,研究稀有金属元素的加入对3种合金系组织结构及力学和电学性能的影响。合金相在真空高频炉中熔炼。首先用X射线衍射仪和金相显微镜对合金相的显微组织和结构进行分析,用电桥、涡流导电仪测量合金相的电阻率,再用AG-X100KN型拉力试验机测量合金相的力学性能。结果表明：稀有金属元素的加入可以有效地细化合金相的显微组织,并且提高合金相的熔点、密度、力学性能和电阻率,但是合金相的延伸率有所降低。     

Study of the Splat Microstructure, Splat-Substrate Interface, and the Effects of Substrate Heating on the Splat Formation for Ni-Cr Particles Plasma Sprayed on to Aluminum Substrates

Roughening of the substrate, for instance by grit-blasting or etching, is often used before plasma spraying in order to provide a high degree of roughness that promotes mechanical interlocking of the sprayed coating and consequently improved adhesion. This study investigates the morphology and microstructure of NiCr splats formed on such rough Al substrates, where roughness was generated by a number of methods including grinding and etching. Cross sections of the splats and the splat-substrate interface were examined using a range of electron microscopy techniques. Localized substrate melting and chemical mixing with the splat material was observed, forming very particular structures. The formation of various oxides phases and voids was also noted and found to increase, along with the degree of the substrate melting, with increasing substrate roughness. The structures observed were related to the spray conditions and substrate morphology.     

Circle approximation for CADCAM using orthogonal C cubic B-splines

A method to approximate a circular arc of any subtended angle with orthogonal C² cubic B-splines is presented. The approach is to specify end points and end tangent directions and to give extra points lying on the span to ensure the required level of accuracy. The critical elements are to use a parameterisation that is optimum for circular data and to determine the tangent magnitudes at the end points. The data can be sampled in any way, although evenly spaced data requires less points to achieve a given accuracy. The method is general and does not depend on any iterative schemes to determine the parameterisation, knot values or tangent magnitudes.     

M2O3-M′2O3系相图中间化合物熔点的计算机预报

应用原子参数－人工神经网络研究了ＭＭ′Ｏ３型的复氧化物的熔点与原子参数之间的关系,并利用已知样本集训练的人工神经网络对ＭＭ′Ｏ３型复氧化物的熔点用“留一法”进行了预报,预报结果与实测值符合较好,误差一般小于５％。研究结果表明,选择适当的原子参数－人工神经网络算法可以用于Ｍ２Ｏ３Ｍ′２Ｏ３系形成的ＭＭ′Ｏ３型复氧化物的熔点的预报。     

Electrical resistivities and phase transformations of lanthanum,cerium, praseodymium,and neodymium

The electrical resistivities of high purity lanthanum, cerium, praseodymium, and neodymium were investigated as a function of temperature over the range from room temperature to near the melting points of the metals. Transformation temperatures were observed in these metals which were confirmed by supplementary X-ray diffraction studies.     

Phase diagram of the CsBr-CaBr2 system

The phase diagram of the CsBr-CaBr2 system was re-determined by using differential thermal analysis and high ternperature and room ternperature X-ray diffraction analysis. It is concluded that there are three intermediate compounds in this system： a.congruently melting compound, CsCaBr3, with a melting point of 823℃ and two incongruently melting compounds, Cs2CaBr4 and Cs3Ca2Br7, whose peritectic points being 597℃ and 635℃, respectively. X-ray diffraction analysis indicated that compound CsCaBr3 is of slightly distorted perovskite structure.     

Size-dependent cohesive energy,melting temperature,and Debye temperature of spherical metallic nanoparticles

It is necessary to theoretically evaluate the thermodynamic properties of metallic nanoparticles due to the lack of experimental data. Considering the surface effects and crystal structures, a simple theoretical model is developed to study the size dependence of thermodynamic properties of spherical metallic nanoparticles. Based on the model, we have considered Co and Cu nanoparticles for the study of size dependence of cohesive energy, Au and Cu nanoparticles for size dependence of melting temperature, and Cu, Co and Au nanoparticles for size dependence of Debye temperature, respectively. The results show that the size effects on melting temperature, cohesive energy and Debye temperature of the spherical metallic nanoparticles are predominant in the sizes ranging from about 3 nm to 20 nm. The present theoretical predictions are in agreement with available corresponding experimental and computer simulation results for the spherical metallic nanoparticles. The model could be used to determine the thermodynamic properties of other metallic nanoparticles to some extent.     

熔模铸铝成型质量控制

通过对铝合金熔模精密铸造熔炼、浇注现场调研,发现了大炉工序在生产中存在的成型质量问题.根据分析,提出了成型质量控制要点及缺陷的控制方法.对熔炼工具、熔炼过程、变质剂、浇注过程等工艺参数都做了阐述.     

DD9镍基单晶高温合金固溶处理初熔组织研究

研究了DD9单晶合金固溶处理过程中组织的变化以及初熔组织的生成机理。结果表明,初熔组织分为两类,即γ/γ′共晶组织熔化生成的不规则初熔组织及固溶微孔熔化生成的规则初熔组织。初熔组织严重降低铸件的高温性能,在1100℃、137 MPa条件下,初熔组织使铸件的使用寿命缩短35h。两种初熔组织都可以通过延长较低温度下的保温时间,促进元素的扩散来消除。     

Analysis of the Zn-Se system

The Zn-Se phase diagram is reanalyzed with an associated solution model for the liquid, new Se-rich liquidus points, and a new Gibbs energy of formation for ZnSe(s). After the liquid model parameters are fixed by a best fit to the liquidus points, the entire liquidus is generated as well as the partial pressures of Zn and of Se₂ along the ZnSe(s) three-phase curve, isotherms for the enthalpy of mixing, and the isotherm for the activity coefficients at the 1799 K melting point of ZnSe(s).     

PPS／PES共混物相容性的研究

聚苯硫醚（PPS）和聚醚砜（PES）树脂都具有较好的耐腐蚀性和较高的耐热性能,这2种热塑性聚合物共混改性可能会得到具有优良性能的共混物。采用差示扫描量热法（DSC）分析共混物的玻璃化转变温度（Tg）及结晶熔融情况,利用扫描电镜观察共混物的形貌结构,行在氮气气氛下用热灭平分析共混物的耐热性能。结果表明：PPS／PES共混物具有2个Tg,且这2个Tg都介于纯聚合物的Tg之间;共混物断面形态比较均匀,两相界而比较模糊,表明共混物为部分相容体系;随着PPS组分的增加,结晶熔融热也逐渐增大,说明PES降低丁PPS的结晶度。用热天平对共混物的耐热性能进行了研究,结果表明共混物在不同PPS／PES比例下耐热性能并没有发生明显变化。     

Analysis of the Zn-Se system

The Zn-Se phase diagram is reanalyzed with an associated solution model for the liquid, new Se-rich liquidus points, and a new Gibbs energy of formation for ZnSe(s). After the liquid model parameters are fixed by a best fit to the liquidus points, the entire liquidus is generated as well as the partial pressures of Zn and of Se₂ along the ZnSe(s) three-phase curve, isotherms for the enthalpy of mixing, and the isotherm for the activity coefficients at the 1799 K melting point of ZnSe(s).     

Design of new face-centered cubic high entropy alloys by thermodynamic calculation

A new face-centered cubic (fcc) high entropy alloy system with non-equiatomic compositions has been designed by utilizing a CALculation of PHAse Diagram (CALPHAD) - type thermodynamic calculation technique. The new alloy system is based on the representative fcc high entropy alloy, the Cantor alloy which is an equiatomic Co- Cr-Fe-Mn-Ni five-component alloy, but fully or partly replace the cobalt by vanadium and is of non-equiatomic compositions. Alloy compositions expected to have an fcc single-phase structure between 700 °C and melting temperatures are proposed. All the proposed alloys are experimentally confirmed to have the fcc single-phase during materials processes (> 800 °C), through an X-ray diffraction analysis. It is shown that there are more chances to find fcc single-phase high entropy alloys if paying attention to non-equiatomic composition regions and that the CALPHAD thermodynamic calculation can be an efficient tool for it. An alloy design technique based on thermodynamic calculation is demonstrated and the applicability and limitation of the approach as a design tool for high entropy alloys is discussed.     

Low-melting-point titanium-base brazing alloys—part 1: Characteristics of two-, three-, and four-component filler metals

The melting point, microstructure, phase, and electrochemical behavior of Ti-21Ni-15Cu alloy, together with two-, three-, and four-component low-melting-point titanium-base brazing alloys, are presented in this paper. Five filler metals were selected for the study, in which melting points were measured by differential thermal analysis, phases identified by x-ray diffractometry, and corrosion behaviors tested by potentiodynamic polarization. The experimental results show that the three-component Ti-15Cu-15Ni and the newly developed Ti-21Ni-14Cu alloys exhibit the combination of lower melting point and superior corrosion resistance compared to the two-and four-component titanium alloys, 316L stainless steel, and a Co-Cr-Mo alloy in Hank’s solution at 37 °C. On a short time basis, the presence of Ti₂Ni and Ti₂Cu intermetallics in the Ti-15Cu-15Ni and Ti-21Ni-14Cu alloys should not be preferentially dissolved in galvanic corrosion with respect to the dissimilar Ti-6Al-4V alloy.     

定向共晶组织的熔化行为

应用定向凝固／重熔技术研究了Ａｌ－Ｃｕ，Ａｌ－Ｎｉ和Ａｌ－Ｓｉ合金定向生长共晶组织的熔化行为。实验结果表明：共晶组织的熔化过程与共凝固生长过程之间不存在完全的互道性。无论是规则片状或棒状共晶组织，或是不规则片状共晶组织，其熔化过程都是共晶组织的两相首先在熔化界面上同时分解，形成各自的分散相，然后这些成分不同的分散相经过进一步溶解混合才形成成分均匀的单一液相。     

铸造工艺对双相不锈钢泵体裂纹的影响

本文针对双相不锈钢泵体制造过程的关键点和难点,在铸造工艺、冶炼工艺、热处理工艺方面采取了多项技术措施,成功解决了双相不锈钢泵体的裂纹问题。     

Calculation of the thermal cycles of points in automatic welding and surfacing taking special features of melting of parent metal into account

It is shown that the well-known equations proposed by N.N. Rykalin for calculating temperatures and also the main parameters of the thermal cycles of points in automatic welding and surfacing with the allowance made for the factors associated with the melting of parent metal should be corrected.     

Study on the designing rules and processability of porous structure based on selective laser melting (SLM)

Porous structures are widely used in medical implant, aerospace and other light-weight manufacturing fields. The research on processability and fabricating process are of great importance to laser addictive manufacturing of porous structure, therefore formulating several rules for SLM fabrication of porous structure is necessary. This article had studied the designing rules and the key points to fabricate the porous structure precisely based on selective laser melting (SLM). In order to obtain the fabricating effect of the pre-designed porous structure, besides optimizing fabricating process, there are still a few problems to be solved gradually, including the critical inclined angle, the fabricating resolution, powder adhesion, designing unit cell and porous structure that fit for SLM process. Through the experiments of fabricating overhanging structures with different inclined angles, the critical inclined angle for designing the porous structure was got. Through designing the thin walls and cylinders with different geometrical dimensions, the SLM fabricating resolution is obtained. Then, based on the critical inclined angle and the geometrical resolution, the octahedral unit cell structure and corresponding design rules that fitted for SLM process were proposed. At last, the experiment of fabricating porous structure was conducted and the pore's sizes were also measured. The results proved that the porous structure can be well fabricated by SLM. This study provides theoretical basis for designing and manufacturing of controllable porous structure based on SLM technique.     

合金元素对6063铝合金阶梯焊中温钎料性能的影响

运用正交试验法,通过改变Si,Cu,Ni元素以及混合稀土RE元素的配比,研究含量的变化对Al-Si-Cu-Ni-RE钎料的熔点、铺展性以及抗剪强度的影响,并通过扫描电镜及能谱分析了钎料内部显微组织;通过研究发现,钎料的成分及加热温度是影响铺展面积的主要因素;对钎料显微组织分析可知,钎料中黑色的脆性θ(CuAl2)相和区域偏析的絮状相不利于接头的性能,而具有面心立方固溶体的基体相α(Al)以及球状聚集的Si相,使得钎料的力学性能优良.结果表明,对钎料熔点的影响方面,Cu元素的影响最大,其次为Ni,Si,RE元素,钎料的熔点随着Cu元素含量的增加而急剧下降.     

First-principles calculations of vacancy–solute element interactions in body-centered cubic iron

We have studied the vacancy–solute atom interactions in body-centered cubic Fe by means of first-principles calculations to obtain a better understanding of them for the application of ferritic steels, which are very important structural materials for fission and fusion reactors. The interactions between a vacancy and carbon/nitrogen interstitial atoms are studied in detail to obtain the binding energies and stable structures of the complexes. Substitutional atoms of 3d transition metals, such as Sc, Ti, V, Cr, Mn, Co, Ni, Cu and Zn, and of other important elements Si, P, S and Mo, are also studied to obtain their binding energies with a vacancy. The origin of the binding energies is discussed from the viewpoints of electronic structures and the distortion of the crystalline lattice.