Bi对铝基滑动轴承合金力学及抗咬合性能的影响

以Al-Cu-Mg合金为基体,研究了添加低熔点组元Bi后合金的微观组织、力学性能及抗咬合性能。采用XRD分析了材料的物相组成,利用SEM和EDS观察了合金的微观组织、断口形貌、磨损界面形貌。结果发现,添加低熔点组元Bi后,合金中出现球状富Bi相,当富Bi相颗粒较小时,其基本由Mg_3Bi_2相组成;当富Bi相颗粒较大时,其以Mg_3Bi_2为核,外部包裹一层Bi,形成了核壳组织。抗拉强度及硬度检测发现,添加2.6%的Bi后合金抗拉强度降低了10%,伸长率降低了21%,硬度降低了8.5%,说明Bi对合金力学性能具有一定的削弱作用。摩擦磨损试验发现,添加Bi后合金抗咬合能力明显提升,承载力从1 700 N增加到5 500 N,且在磨损表面发现带状富Bi相涂覆在磨损表面,起到减摩自润滑作用。     

Cu-P中间合金的快速凝固处理对Al-Si合金耐磨性的影响

研究了Cu-P中间合金的快速凝固处理对Al-Si合金耐磨性的影响.TEM分析表明:在冷却速度为105～106℃/s时,Cu-P中间合金薄带的组织由纳米晶和少量的非晶组织组成,而且Cu-P中间合金中的Cu3P的晶粒尺寸由5～40 μm下降到30～50 nm.结果表明,由于强度和硬度的提高,用薄带状中间合金改性处理的Al-Si合金的耐磨性要高于用块状中间合金改性处理的Al-Si合金:磨损率由0.86％下降到0.39％.因此,用熔体快淬Cu-P中间合金进行改性处理是提高Al-Si合金的耐磨性的有效办法.     

Al-Bi-Ce-Cu难混溶合金的凝固组织和耐磨性

本文研究了Al-Bi-Ce-Cu难混溶合金的凝固组织和耐磨性能。实验结果表明,添加Ce到Al-Bi合金中,原位生成的棒状化合物Bi₂Ce作为异质形核质点,促进了Bi相的形核,所制备难混溶合金中富Bi相颗粒弥散分布。添加Cu到Al-Bi-Ce合金中生成了硬质相Al₂Cu,硬质相增强了基体的硬度,进而提高了合金的耐磨性能,降低了合金的耐磨性系数。因此Al-Bi-Ce-Cu合金,不仅具有富Bi相颗粒弥散分布的组织,同时还具有高的耐磨性能,有很强的实际应用价值。     

Sb,Bi和Fe对Cu-8P共晶合金熔点和组织的影响

采用NETZSCH DSC 404型差示扫描量热仪(DSC)、扫描电子显微镜(SEM)等手段研究了添加元素Sb,Bi和Fe对Cu-8P共晶合金熔点和组织的影响.实验结果表明:Sb,Bi和Fe均能降低Cu-8P合金的熔点.一定量的Sb与Cu,P形成低熔点相,从而大幅降低了Cu-8P合金的熔点,使其熔点降低近200℃;加入少量Bi后,Bi与Cu在共晶团晶界上形成熔点为270℃左右的低熔点化合物,且Bi的加入明显细化Cu-8P合金共晶团,从而使Cu-8P合金的熔点降低;加入Fe能明显细化Cu-8P合金的共晶团,使层片间距由8 μm减为2μm以下,并使共晶团由层片状向短棒状转变,虽然Fe与Cu形成熔点为806℃的高温相,但Fe的细化作用使得Cu-8P合金的熔点降低,但降低幅度不大.同时得出形成低熔点的化合物(相)和细化晶粒是降低合金熔点的有效途径.     

多向强应变和时效处理对Al-Zn-Mg-Cu合金摩擦磨损性能的影响

为探明多向强应变和时效处理对Al-Zn-Mg-Cu合金的显微组织、力学性能和摩擦磨损性能的影响，以多向锻造和时效处理工艺加工Al-Zn-Mg-Cu合金，对其显微组织进行了表征，并对其力学性能和摩擦磨损性能进行了测试。研究结果表明：经多向锻造加工后，Al-Zn-Mg-Cu合金的强度和硬度提高，但伸长率和耐磨性却大幅度下降。锻造合金再经120℃×1320 min时效处理后，强度和硬度进一步提高，伸长率得到明显改善，耐磨性增强。Al-Zn-Mg-Cu合金的抗拉强度、硬度和伸长率分别达到644 MPa、210 HV和14.9%,耐磨性较挤压T6态提高了68.3%。由于高的硬度和加工硬化使耐磨性增强，并且晶界析出相的不连续分布降低了晶界处的应力集中，从而也改善了Al-Zn-Mg-Cu合金的耐磨性。     

Sn,Bi对易切削Al-Mg-Si合金组织与性能的影响

采用力学性能测试、X射线衍射物相分析、SEM背散射扫描和能谱分析、金相试验技术,研究了时效工艺对固溶-冷拉处理过程中,用Sn和Bi微合金化对无Pb易切削Al-Mg-Si合金棒材显微组织结构特征和力学性能的影响。结果表明,其最佳的时效热处理工艺为170℃×8h。单独添加Sn的合金的物相组成除了Al基体,还有低熔点Mg2Sn和AlMnSi相,而联合添加Sn,Bi的合金组织由Al基体,低熔点Mg3Bi2与少量Sn和Bi单质以及AlMnSi相组成。     

Cr-Bi对Mg-8Zn-4Al合金铸态组织及时效沉淀相演变的影响

利用扫描电子显微镜(SEM)和X射线衍射(XRD)等分析手段研究了Bi、Cr-Bi复合添加对Mg-8Al-4Zn合金铸态组织及时效沉淀相演变的影响。结果表明:Cr-Bi复合添加能有效改善合金的铸态组织,使连续网状相断开呈短杆或颗粒状。Bi、Cr-Bi复合添加的合金经350℃×12 h+160℃时效,其沉淀硬化曲线呈现典型的温时效。Cr-Bi复合添加的合金时效初期硬化速率较高,20 h就达到峰值硬度的97%,时效48 h达到峰值硬度92.44 HV,过时效阶段硬度下降速度比较缓慢。Mg-8Zn-4Al-0.5Bi合金经350℃×12 h+160℃×120 h时效后主要有MgZn2、Mg3Bi2和单Bi相,呈短杆或细小颗粒状弥散分布在基体上;Cr-Bi复合添加的合金经350℃×12 h+160℃×144 h时效后,除短杆或细小颗粒状的MgZn2相外还有Cr、Al12Cr3等沉淀相,没有发现粗大的MgZn相,且沉淀相与单独添加Bi经120 h时效的合金相比更加细小、致密、弥散均匀分布。     

Ag颗粒增强Sn-58Bi无铅钎料力学性能研究

在Sn-58Bi钎料中添加Ag颗粒,制备颗粒增强的低温无铅钎料,研究了钎料焊接头力学性能。本文研究结果表明：Sn-58Bi合金中添加少于1wt％的Ag会均匀分布在基体合金中,提高了合金钎料的拉伸强度。钎料在100℃恒温时效试验中,Bi相的粗化趋势明显低于Sn-58Bi共晶钎料,提高了合金钎料的组织稳定性。钎料的拉剪强度则随着钎料中Ag含量的增加而升高,但量超过1wt％时,拉剪强度又会下降。     

热处理对高硼低碳铸钢组织和耐磨性的影响

研究了淬火温度分别为940、1 000、1 060℃时高硼低碳铸钢显微组织、力学性能和耐磨性的变化规律。结果表明:不同淬火温度下,钢的组织均由马氏体+硼化物+少量的残余奥氏体组成。随着淬火温度逐渐升高,硼化物由连续的网状向孤立的杆、块和粒状转化;硬度先上升后平缓下降,磨损失重量先下降后增大;经1 000℃×1.5 h水冷淬火+200℃×3 h回火后,钢的硬度上升到最大值53 HRC,磨损失重量下降到最小值14.2 mg,相对940℃时的硬度和耐磨性分别提高了1.07倍和2.28倍。     

回火温度对铁基多元合金堆焊层组织及耐磨性的影响

研究了回火温度对铁基多元合金堆焊层组织及耐磨性的影响。结果表明，该堆焊层回火后具有二次硬化现象；当回火温度低于400℃，其硬度变化不明显，超过600℃，硬度明显下降；在560℃回火2h．具有优异的耐磨性，且组织与耐磨性有良好的对应。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。