用多元线性回归法预测镍基高温合金的抗氧化性

用静态氧化法研究了3种铸造镍基高温合金K35、K44、K46在800℃及900℃的高温氧化动力学行为.结果表明,3种合金的氧化动力学曲线均符合抛物线规律,其中氧化速度常数为合金成分中每种元素作用的综合结果.用多元线性回归法计算了25种镍基高温合金在900℃氧化过程的作用系数,并给出了3种试验合金的氧化动力学回归方程,与3种合金的实验结果相比,相对误差小于13％。

低膨胀高温合金抗氧化性能预测的研究

通过测定六种不同成分的低膨胀高温合金氧化增重曲线， 提出合金元素作用系数的概念， 利用分析得到的合金元素作用系数对实验合金的氧化增重进行预测计算，其结果与实验结果吻合得很好。利用合金元素作用系数的概念和本研究所提出的方法可对低膨胀高温合金的氧化增重提供预测计算， 借此可减少研究低膨胀高温合金氧化特性的试验工作量， 为今后低膨胀高温合金的发展打下了基础。

Recycling of metals from waste Sn-based alloys by vacuum separation

In order to recycle waste Sn-based alloys, the vapor-liquid phase equilibrium composition diagrams of Sn-Pb, Sn-Sb and Sn-Zn binary systems were calculated. The calculated results indicate that Pb, Sb and Zn can be separated from Sn effectively. Based on the above calculation, the industrial experiments of vacuum distillation of Sn-Pb alloy, Sn-Pb-Sb alloy, Sn-Pb-Sb-As alloy, crude Sn and Sn-Zn alloy with different contents were carried out. The experimental results show that Pb(>99% Pb) and Sn(≤0.003% Pb) were obtained simultaneously while Sn-Pb alloy was subjected to vacuum distillation; the crude Sn(>90% Sn, ≤ 2% Pb, ≤6% Sb) and crude Pb(≤2% Sn) were obtained simultaneously while a single vacuum distillation was carried out for Sn-Pb-Sb alloy; the Pb and Bi contents in the Sn ingot(99.99% Sn) achieve the grade A of GB/T 728—2010 standard, more than 50% of As and Sb was removed after vacuum distillation of crude Sn; Zn(<0.002% Sn) and Sn(about 3% Zn) were obtained while vacuum distillation of Sn-Zn alloy was conducted at 1173 K, 20-30 Pa for 8-10 h.

高铬铸铁芯焊条堆焊层组织分析

基于焊芯过渡合金元素的技术思路,研制了高铬合金铸铁同质堆焊焊条.分析了不同药皮堆焊焊条的堆焊层组织及性能,定量表征了合金元素的过渡系数.结果表明,通过焊芯过渡合金元素的高铬合金铸铁堆焊焊条可获得组织和性能均匀的堆焊层.合金过渡系数高于85%.碱性药皮堆焊焊条堆焊层为亚共晶成分高铬合金铸铁,组织由奥氏体γ+马氏体M+碳化物Cr7C3组成.堆焊层硬度为44.5～56.5 HRC.碱性石墨化型药皮堆焊焊条堆焊层组织由初生碳化物Cr7C3+马氏体M+碳化物Fe7C3+少量石墨G组成,堆焊层硬度可达59～67 HRC.

喷丸成形及强化对2024HDT-T351板材疲劳特性的影响

目的获得喷丸成形及喷丸强化工艺对2024HDT-T351板材疲劳特性的影响规律。方法设计了一种不传载的含紧固件单细节结构疲劳品质试验件,各组试验件相同,变化各组的喷丸参数,进行了试验基准组、喷丸强化组和4种不同参数喷丸成形组、4种不同参数喷丸成形后喷丸强化组的疲劳试验。结果通过疲劳试验和数据处理,获得了各组的疲劳性能、细节疲劳额定值和在相应应力水平下的疲劳寿命。试验结果表明,所有组的细节疲劳额定值均高于试验基准组,其中喷丸强化试验组的疲劳性能提高了24%,喷丸成形试验组的疲劳性能提高了9%~13%,喷丸成形后喷丸强化试验组的疲劳性能提高了9%~24%。结论给出了2024HDT-T351板材喷丸成形及强化疲劳分析合金和表面处理系数B。2024HDT-T351铝合金板材经喷丸强化后、经大弹丸喷丸成形后和经大弹丸喷丸成形后喷丸强化,疲劳分析时合金和表面处理系数B可保守取1.2、1.05、1.05。

X射线测厚仪标样的国产化

叙述了Ｘ射线测厚仪及标样盒的作用，分析标样盒内标样的化学成分，介绍使用纯铝材料制作标样的方法．

Calculation of hydrogen solubility in molten alloys

A thermodynamic model was developed to calculate the hydrogen solubility in molten alloys based on the hydrogen solubility in constitutional pure liquid metals and their interaction parameters. The calculated results have a good agreement with the documented experimental results. The closer the molten alloy to an ideal liquid is, the more accurate the calculated results are. The compound forming ability and molar mixing heat of the constitutional elements take important roles in influencing the hydrogen solubility in molten alloys.

Microstructure evolution and thermal expansion of Cu-Zn alloy after high pressure heat treatment

The thermal expansion coefficients of Cu-Zn alloy before and after high pressure treatment were measured by thermal expansion instrument in the temperature range of 25？700 ℃,and the microstructure and phase transformation of the alloy were examined by optical microscope,X-ray diffractometer（XRD） and differential scanning calorimeter（DSC）.Based on the experimental results,the effects of high pressure treatment on the microstructure and thermal expansion of Cu-Zn alloy were investigated.The results show that the high pressure treatment can refine the grain and increase the thermal expansion coefficient of the Cu-Zn alloy,resulting in that the thermal expansion coefficient exhibits a high peak value on the α-T curve,and the peak value decreases with increasing the pressure.

Alloy gene Gibbs energy partition function and equilibrium holographic network phase diagrams of Au_3Cu-type sublattice system

Taking Au3Cu-type sublattice system as an example, three discoveries have been presented. First, the fourth barrier to hinder the progress of metal materials science is that today’s researchers do not understand that the Gibbs energy function of an alloy phase should be derived from Gibbs energy partition function constructed of alloy gene sequence and their Gibbs energy sequence. Second, the six rules for establishing alloy gene Gibbs energy partition function have been discovered, and it has been specially proved that the probabilities of structure units occupied at the Gibbs energy levels in the degeneracy factor for calculating configuration entropy should be degenerated as ones of component atoms occupied at the lattice points. Third, the main characteristics unexpected by today’s researchers are as follows. There exists a single-phase boundary curve without two-phase region coexisting by the ordered and disordered phases. The composition and temperature of the top point on the phase-boundary curve are far away from those of the critical point of the Au3Cu compound; At 0 K, the composition of the lowest point on the composition-dependent Gibbs energy curve is notably deviated from that of the Au3Cu compounds. The theoretical limit composition range of long range ordered Au3Cu-type alloys is determined by the first jumping order degree.

Alloy gene Gibbs energy partition function and equilibrium holographic network phase diagrams of AuCu_3-type sublattice system

Taking AuCu3-type sublattice system as an example, three discoveries have been presented: First, the third barrier hindering the progress in metal materials science is that researchers have got used to recognizing experimental phenomena of alloy phase transitions during extremely slow variation in temperature by equilibrium thinking mode and then taking erroneous knowledge of experimental phenomena as selected information for establishing Gibbs energy function and so-called equilibrium phase diagram. Second, the equilibrium holographic network phase diagrams of AuCu3-type sublattice system may be used to describe systematic correlativity of the composition?temperature-dependent alloy gene arranging structures and complete thermodynamic properties, and to be a standard for studying experimental subequilibrium order-disorder transition. Third, the equilibrium transition of each alloy is a homogeneous single-phase rather than a heterogeneous two-phase, and there exists a single-phase boundary curve without two-phase region of the ordered and disordered phases; the composition and temperature of the top point on the phase-boundary curve are far away from the ones of the critical point of the AuCu3 compound.

Effect of liquid diffusion coefficients on microstructure evolution during solidification of Al356.1 alloy

（The effect of liquid diffusion coefficients on the microstructure evolution during solidification of primary （Al） phase in Al356.1 alloy was investigated by means of the phase-field simulation using two sets of diffusion coefficients in liquid phase, while fixing other thermophysical and numerical parameters. The first set is only with impurity coefficients of liquid phase in Arrhenius formula representing only the temperature dependence. While the second set is with the well-established atomic mobility database representing both temperature and concentration dependence. For the second set of liquid diffusion coefficients, the effect of non-diagonal diffusion coefficients on the microstructure evolution in Al356.1 alloy during solidification was also analyzed. The differences were observed in the morphology, tip velocity and composition profile ahead of the tip of the dendrite due to the three cases of liquid diffusivities. The simulation results indicate that accurate databases of mobilities in the liquid phase are highly needed for the quantitative simulation of microstructural evolution during solidification.

Quality index and hot tearing susceptibility of Al-7Si-0.35Mg-xCu alloys

The effects of Cu addition（0.5%, 1%, 1.5%, 2%, and 3%, mass fraction） on the quality index（Qi） and hot tearing susceptibility（HTS） of A356 alloy were investigated. According to the results, Cu addition up to 1.5% increases the Qi by almost 10%, which seems to be due to its solid solution strengthening and dispersion hardening effect of Cu-rich Al2Cu and AlMgCuSi compounds. However, further addition of Cu（up to 3%） decreases the Qi by almost 12%, which is likely due to the reduction of tensile strength and elongation caused by increased volume fraction of brittle Cu-rich intermetallics and microporosities in the microstructure. It is also found that Cu increases the HTS of A356 alloy measured by constrained rod casting method. According to the thermal analysis results, Cu widens the solidification range of the alloy, which in turn, decreases its fluidity and increases the time period during which the mushy-state alloy is exposed to the hot tearing susceptible zone. SEM examination of the hot tear surfaces in high-Cu alloys also demonstrates their rough nature and the occurrence of interdendritic/intergranular microcracks as convincing evidences for the initiation of hot tears in the late stages of solidification in which there is not enough time for crack healing.

Measurement of friction coefficient in aluminum sheet warm forming

Aluminum alloy sheets are used more and more to manufacture auto panels. Because the friction behavior is very complicated, it is necessary to study the friction during the aluminum sheet warm forming process. The author has designed a new probe sensor based on an online tribotest method which directly measures friction coefficient in the forming process. Experiments of cup drawing have been conducted and the friction coefficients under different forming conditions have been measured. The results indicate that the forming parameters, such as forming temperature, blankholding force and lubrication status have great effect upon the friction coefficient.

Thin Film Chip Resistors with High Resistance and Low Temperature Coefficient of Resistance

High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...

Calculation and experimental study on heating temperature field of super-high strength aluminum alloy thick plate

Stepped heating treatment has been applied to aluminum alloy thick plate to improve the mechanical performance and corrosion resistance.Accurate temperature control of the plate is the difficulty in engineering application.The heating process,the calculation of surface heat transfer coefficient and the accurate temperature control method were studied based on measured heating temperature for the large-size thick plate.The results show that,the temperature difference between the surface and center of the thick plate is small.Based on the temperature uniformity,the surface heat transfer coefficient was calculated,and it is constant below300°C,but grows greatly over300°C.Consequently,a lumped parameter method(LPM)was developed to predict the plate temperature.A stepped solution treatment was designed by using LPM,and verified by finite element method(FEM)and experiments.Temperature curves calculated by LPM and FEM agree well with the experimental data,and the LPM is more convenient in engineering application.

Spatial interfacial heat transfer and surface characteristics during gravity casting of A356 alloy

As one of the key boundary conditions during casting solidification process, the interfacial heat transfer coefficient (IHTC) affects the temperature variation and distribution. Based on the improved nonlinear estimation method (NEM), thermal measurements near both bottom and lateral metal-mold interfaces throughout A356 gravity casting process were carried out and applied to solving the inverse heat conduction problem (IHCP). Finite element method (FEM) is employed for modeling transient thermal fields implementing a developed NEM interface program to quantify transient IHTCs. It is found that IHTCs at the lateral interface become stable after the volumetric shrinkage of casting while those of the bottom interface reach the steady period once a surface layer has solidified. The stable value of bottom IHTCs is 750 W/(m^2·℃), which is approximately 3 times that at the lateral interface. Further analysis of the interplay between spatial IHTCs and observed surface morphology reveals that spatial heat transfer across casting-mold interfaces is the direct result of different interface evolution during solidification process.

Microstructural evolution and microsegregation in directional solidification of hypoeutectic Al−Cu alloy:A comparison between experimental data and numerical results obtained via phase-field model

The objective of the work is focused on predictions of microsegregation,solidification speed,dendritic arm spacings and dendrite morphology by phase-field model.The numerical results were compared with experimental data.The experimental values for cooling rates and effective partition coefficient were adopted during calculations.The results of microsegregation through phase-field model show excellent agreement with the experimental data.Such excellent agreement is because cooling rates,effective partition coefficient and back-diffusion of solute are considered in the model.For solidification speed,the calculation results show good agreement with the experimental data.Tertiary dendritic arm spacing calculated with phase-field model is compared with experimental data.The results show good agreement between them.The dendrite arm spacing varies with position because high cooling rates are responsible for the refinement effect on microstructure.Finally,two-dimensional simulation produced a dendrite that is similar to that found in the experiment.

Modeling effects of constituents and dispersoids on tensile ductility of aluminum alloy

The modeling effects of constituents and dispersoids on the tensile ductility of aluminum alloy were studied.The results show that the tensile ductility decreases with the increase of the volume fraction and size of constituents.Thus,purification can improve the tensile ductility by decreasing the volume fraction of constituents(normally compositions of Fe and Si)and the first-class microcracks.The model also indicates that the tensile ductility decreases with the increase in the volume fraction of dispersoids.Decreasing the volume fraction of dispersoids along the grain boundaries by proper heat-treatment and improving the cohesion strength between dispersoids and matrix can also improve the tensile ductility by decreasing the volume fraction of the second-class microcracks.

Investigation of mechanical and diffusion properties in bcc Ti−Nb−Zr−Sn alloys via a high-throughput method

The mechanical and diffusion properties of bcc Ti−Nb−Zr−Sn alloys in the Ti-rich corner were analyzed through a high-throughput method with the combination of nanoindentation and diffusion couple techniques.Nine groups of quaternary Ti−Nb−Zr−Sn diffusion couples were prepared after annealing at 1273 K for 25 h.The composition-dependent mechanical properties were determined by nanoindentation and electron probe microanalysis(EPMA)techniques.Moreover,the corresponding interdiffusion coefficients were confirmed from the composition gradients of the quaternary diffusion couples using a pragmatic numerical inverse method.A composition-dependent database on the mechanical and diffusion properties was utilized to discuss the processability during the hot working.The results reveal that the solute elements Nb and Sn are strictly controlled to increase the hardness and wear resistance of Ti−Nb−Zr−Sn alloys,and the additional element Zr is mainly useful to improve the processability during the hot working.

Experimental and CFD investigations on cooling process of end-quench test

The microstructure of an alloy is affected intensively by the cooling process.To figure out the inherent relation between the cooling rate and microstructure of an advanced nickel-based superalloy,experimental and numerical studies on the cooling process were conducted.Specifically,the measurement was performed concerning both the temperature of the specimen during the end-quench test and the size of the secondaryγ′phase of the specimen after that.The heat transfer coefficient of the quenched surface was determined by the inverse heat transfer method for simulation.The results show that the cooling rate of the quenched surface exceeds 1574 K/min.Based on the averaged cooling rate obtained from the simulation and the measured size of the secondaryγ′phase,an empirical correlation in a double logarithmic relationship between them is proposed.The relationship is verified by the experiment with specified cooling rates.