铬基钨镍钼高耐磨合金耐磨机理及产业化

本文研究了铬基钨镍钼高耐磨合金的耐磨机理。重点分析了铬基钨镍钼高耐磨合金的铸造工艺流程、铸造用废砂回收再生树脂砂的利用技术以及基于铬基钨镍钼高耐磨合金的耐磨产品。结果表明:铬基钨镍钼高耐磨合金的各种成分在不同工况中具有良好的耐磨性能。     

Refinement mechanism of in-situ Al4C3 particles on AZ91 magnesium alloys

The effects of SrCO3 on the microstructure of AZ91 magnesium alloy were investigated by OM, SEM, EDS, XRD and DTA analyses. The results show that AZ91 magnesium alloy with 1.0% SrCO3 addition has the best refining effect at 730 ℃ for 20 min, the average size of the α-Mg grain in AZ91 matrix alloy is reduced from about 91 μm to 58 μm, with reduction of about 36%. Based on the analysis results of EDS, binding energy, and Gibbs free energy, it is evident that the grain is refined because of the generation of A14 C3 particles which can be used as the crystal nucleus of the magnesium alloy when SrCO 3 is added. Owing to the generation of A14C3 in AZ91 magnesium alloy, the grain boundary is pined and the grain growth is inhibited. In the accession to the Al4C3, small subcooling temperature difference leads to the formation of fine grain microstructure in alloy melt. Fine grain microstructure in AZ91 alloy melt with the addition of SrCO3 can be obtained on the condition of lower undercooling temperature according to the DTA analysis results.     

Calculation of thermodynamic parameters of Mg-Al-Y alloy

By means of Miedema formation enthalpy model with Toop model, the excess free-energy, enthalpies of formation, excess entropies and activity values of all components of Mg-Al-Y ternary alloy were calculated with computer programming. The experimental results show that enthalpies of formation, excess freeenergy and excess entropies of the ternary alloy are negative in the whole content range, the minimum values at 1 123 K are all obtained at x Al=55%, x Y=45%, x Mg=0%, which are-37.969, –30.961 kJ/mol and-6.24 J/(mol·k) respectively. Activity curves show that the activity values of Al and Y in Mg-Al-Y ternary alloy rapidly decrease with the decrease of molar fraction, the values of which are very small when the molar fraction decreases to 0.4. It means that there is a strong interaction between Al and Y and stable compounds can be form in the Mg-Al-Y ternary alloy system.     

First-principles Investigation of the Structural,Electronic and Elastic Properties of Al2Ca and Al4Sr Phases in Mg-Al-Ca（Sr） Alloy

First-principles calculations have been carried out to investigate the structural stabilities, electronic structures and elastic properties of Mg17Al12, Al2Ca and Al4Sr phases. The optimized structural parameters are in good agreement with the experimental and other theoretical values. The calculated formation enthalpies and cohesive energies show that Al2Ca has the strongest alloying ability, and Al4Sr has the highest structural stability. The densities of states （DOS）, Mulliken electronic populations, and electronic charge density difference are obtained to reveal the underlying mechanism of structural stability. The bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio are estimated from the calculated elastic constants. The mechanical properties of these phases are further analyzed and discussed. The Gibbs free energy and Debye temperature are also calculated and discussed.     

高温合金IN690管材挤压损伤模拟

采用有限元软件对高温合金IN690管材挤压损伤进行预测,研究挤压速度对损伤的影响规律,得到不同的挤压条件下的挤压阈值。不同挤压速度下损伤的变化随着挤压速度变化呈现先增大后减小的趋势。模拟摩擦系数为0.01、0.05、0.1、0.2条件下的损伤,在摩擦系数为0.01时,坯料表面比较光滑,损伤比较轻;摩擦系数为0.2时,表面凹凸不平,损伤严重。     

球磨参数及Ni比例对Mg2Ni合金储氢性能影响研究

采用中频感应炉熔炼出铸态Mg2 Ni合金,将Mg2Ni合金与一定量的Ni粉进行混合球磨处理.系统研究在不同Ni粉添加量及球磨时间等条件下所得合金样品的结构及储氢性能.研究表明,随着Ni含量的增大及球磨时间的延长,合金的非晶纳米晶结构逐渐增多;合金的最大放电容量及循环稳定性得到明显提升;合金的表面催化活性及合金体相内的H传输能力都有了显著提高.Ni粉的作用主要在于可促进合金非晶化,同时对合金的放氢过程起到了催化的作用.     

氧化铈对Fe55自熔合金喷焊层组织与性能的影响

通过水雾化方法制备了Fe55自熔合金粉末,并通过在粉末中加入不同稀土量用氧乙炔火焰喷焊的方法在45钢板基材表面制备合金涂层,研究了稀土氧化铈对Fe55自熔合金喷焊层的组织和性能的影响.     

Effect of rare earth samarium addition on the kinetics of precipitation in AI-Cu-Mn casting alloy

The mechanical properties of Al-Cu-Mn casting alloy mainly depend on the morphology, distribution, size, and number ofθ′（Al2Cu） precipitates. In this study, we have analyzed the effect of rare earth samarium （Sm） addition on the kinetics of precipitation in the Al-Cu-Mn casting alloy by using differential scanning calorimetry （DSC） and high-resolution transmission electron microscopy. Thermal ef-fect peaks that are attributed to the formation and the dissolution of Guinier-Preston （GP） zone andθ′phase were identified from the DSC curves. The activation energy ofθ′formation was calculated by using both the Kissinger method and the analytical model, and the corre-sponding results were compared. Results suggest that the activation energy ofθ′formation in Al-Cu-Mn alloy is dramatically higher than that in Al-Cu-Mn-Sm alloy. Accordingly, it is concluded that the addition of rare earth Sm decreases the activation energy ofθ′formation and promotes the formation ofθ′precipitates.     

Anodic behavior and microstructure of Al/Pb-Ag-Co anode during zinc electrowinning简

In order to study the anodic behavior and microstmctures of A1/Pb-Ag-Co anode during zinc electrowinning, by means of potentiodynamic investigations, scanning electron microscopy （SEM） and X-ray diffraction （XRD） analyses, the mechanism of the anodic processes playing on the surface of A1/Pb-0.8%Ag and A1/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured. On the basis of the cyclic voltammograms obtained, information about the corrosion rate of the composite in PbO2 region has been concluded. The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4, but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO4 concentrated in the certain zones after 24 h of anodic polarization. It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO2 and PbSO4 and a, fl-PbO2 penetrated into which, in fact, are the active centers of the oxygen evolution after 24 h of anodic polarization.     

TM-Gd合金系非晶形成能力的热力学研究（I）

在Co-Gd二元系合金体系的热力学优化评估的基础之上,应用CALPHAD （ CALculation of PHAse Diagram）技术,研究此二元非晶合金的玻璃形成能力。本文分析了700 K、800 K时Co-Gd合金中各元素含量对非晶形成能力的影响,预测了非晶形成的最优成分,计算过冷液相中的结晶相形成驱动力。通过与部分实验和非晶共晶点准则的比较可见,本文所做的热力学分析对此二元合金的非晶制备具有一定的理论指导意义。