二次热压法制备SiCp/Al复合材料的耐磨性能研究

采用快速升温二次热压法制备了(10~30)SiC/Al-0.8Si-1.2Mg-0.4Cu复合材料,并研究其与钢球对磨的摩擦磨损规律。结果表明,二次热压变形法能有效抑制剧烈的界面反应,得到高致密的SiCp/Al复合材料。复合材料的摩擦因数随SiC含量增加而增大,大载荷下增幅更明显。试验条件下,SiC/Al复合材料与GCr15钢的摩擦因数在0.3~0.5之间。复合材料的磨损率开始随载荷增大而增大,载荷超过5N后,SiC含量小于15%的试样磨损率继续增大,而SiC含量大于20%的试样的磨损率则急剧减少。这是由于高SiC含量试样在大载荷下表层生成的Al2O3增强了摩擦层。在载荷7N时,30SiC/Al复合材料的磨损率只有1.14×10-3mm3/m,说明该复合材料更适宜在大载荷下应用。     

(SiC,Gr)/Al复合材料的热压法制备及其摩擦磨损性能研究

采用快速升温热压法制备（（1-×）SiC-×Gr）20wt.%/Al-0.8Si-1.2Mg-0.4Cu复合材料,研究其与钢球对磨的摩擦磨损规律。结果表明：快速升温热压法可制备致密性较高的（SiC,Gr）20wt.%/Al复合材料,并有效抑制剧烈的界面反应。复合材料与GCr15钢的摩擦系数随载荷波动不大,随×增大而降低。×0.3时,脱落在摩擦面的石墨较少,摩擦系数下降较慢,×〉0.3后,摩擦系数快速减小。×=0.2和0.3时复合材料的磨损率随载荷增加急剧增大,差别最大达7倍,而×0.05或≥0.6时,SiC与石墨颗粒能协调作用,复合材料具有良好的耐磨性,磨损率随载荷变化较小。×=0.6时,复合材料具有最低的磨损率（8.4×10^-4mm^3/m）,处于超轻微磨损状态。     

摩擦环境对Cu/石墨复合材料摩擦磨损行为的影响

采用热压烧结法制备了Cu/石墨复合材料,并研究了摩擦环境对材料摩擦磨损行为的影响.结果 表明:摩擦环境显著影响了Cu/石墨复合材料的摩擦磨损性能,其摩擦系数在干摩擦时最小(0.15),海水中次之(0.29),去离子水中最大(0.46).但是,其磨损率呈现不同的变化趋势,海水中磨损率最小(7.09×10-14m3/N·m...     

润滑条件下Mg2B2O5/6061Al基复合材料摩擦磨损性能研究

采用自制的机械-超声混合搅拌设备制备出Mg2B2O5/6061Al铝基复合材料,复合材料的体积分数为2%。研究了载荷和滑动速度对基体以及复合材料的摩擦磨损性能的影响。实验结果表明,基体和复合材料摩擦系数总体上随着载荷和滑动速度的增加而减小。基体和复合材料的磨损率随载荷和滑动速度的增加而明显的增大,且基体和复合材料均存在一个临界载荷和临界滑动速度。当载荷和滑动速度到达临界值后,磨损率均急剧增大,此时试样摩擦磨损机制由微观疲劳磨损和磨粒磨损向粘着磨损与剥离磨损转变。     

热压烧结Gr/6061Al复合材料制备与组织性能研究

实验采用了热压烧结的方法制备了1~25vol%片层石墨(Gr)含量的Gr/6061Al复合材料,并采用了纳米铝粉包覆片层石墨的混粉工艺提高片层石墨在铝基体粉末中的分散均匀性。所制备的复合材料中,片层石墨均匀分散在铝基体中,界面结合良好,未发现界面反应产物的存在,通过透射电镜观察到了少层石墨烯的存在。1~15vol% Gr含量的Gr/6061Al复合材料的致密度均高于90%;复合材料的致密度和摩擦系数随着片层石墨含量的增加具有相同的变化趋势,都逐渐降低;石墨含量从1vol%增加到25vol%时,复合材料摩擦系数(COF)呈逐渐降低的趋势;与1vol.%Gr含量的Gr/6061Al复合材料相比,其他Gr含量的复合材料的磨损率均较高。     

硼酸镁晶须增强6061铝基复合材料的干摩擦磨损行为(英文)

研究搅拌铸造工艺制备的硼酸镁晶须增强6061铝基复合材料在干滑动条件下的摩擦磨损性能。复合材料的体积分数为2%,根据增强体种类,材料分别记为:Al基体、Mg2B2O5w/6061Al、ZnO/Mg2B2O5w/6061Al和CuO/Mg2B2O5w/6061Al;讨论磨损速率和摩擦因数之间的关系。结果表明:在4种材料中,ZnO/Mg2B2O5w/6061Al复合材料的磨损率最低。随着载荷和滑动速度的增大,基体和复合材料的摩擦因数和磨损率降低,摩擦磨损机制由轻微磨损机制转向严重磨损机制。     

铜包石墨对酚醛树脂基复合材料摩擦学性能的影响

目的 提高石墨与酚醛树脂的界面结合强度,改善酚醛树脂基复合材料的摩擦学性能。方法 用高温浸渗法制备铜包石墨,并制备铜包石墨-酚醛树脂基复合材料。通过摩擦磨损实验,研究铜包石墨对酚醛树脂基复合材料摩擦学性能的影响,并对比相同成分铜/石墨混合填充酚醛树脂基复合材料的摩擦学性能。通过扫描电子显微镜、能谱仪和光学显微镜对摩擦磨损表面进行分析,研究材料摩擦磨损机理。结果 石墨表面经过金属铜处理后,金属铜由分散的聚集态转变为附着态,制备的铜包石墨颗粒整体分散度高、形状好。铜包石墨-酚醛树脂基复合材料中石墨与基体界面结合紧密,保持了酚醛树脂的连续相结构,摩擦磨损表面相对平整,复合材料平均比磨损率为3.98×10^?6 mm³/(N.m),瞬时摩擦系数波动幅度小,摩擦磨损机理以粘着磨损为主。相同成分制备的铜/石墨混合填充酚醛树脂基复合材料的界面结合度较差,摩擦磨损表面有较多裂痕,复合材料平均比磨损率为7.80×10^?6 mm³/(N.m),瞬时摩擦系数波动幅度大,摩擦磨损机理以磨粒磨损和粘着磨损为主。结论 石墨通过表面金属铜处理,不仅能提高与基体界面结合强度,还能同时有效提高酚醛树脂基复合材料的耐磨性能和摩擦稳定性。     

涂覆及未涂覆Mg_2B_2O_(5w)晶须的6061Al合金干摩擦行为研究

制备了未涂覆、涂覆Cu O和涂覆Zn O的硼酸镁晶须(Mg2B2O5w)增强的6061Al铝基复合材料,研究了外加载荷和滑动速度对6061Al合金以及复合材料的摩擦磨损性能的影响。结果表明,在相同条件下,涂覆Zn O涂层、Cu O涂层、未涂层晶须增强的铝基复合材料和6061Al合金磨损率依次增大;随着载荷和滑动速度的增加,6061Al合金和复合材料的摩擦系数均有下降的趋势,磨损率随之减小。     

自润滑纤维织物复合材料摩擦学性能研究

目的研究MoS_2和石墨填充对自润滑纤维织物复合材料摩擦学性能的影响。方法采用玄武三号栓-盘式摩擦磨损实验机,研究了石墨和MoS_2填充PTFE/棉纤纤维织物在不同载荷条件下的摩擦磨损性能,并采用扫描电镜观察了纤维织物复合材料的磨损表面和微观结构。结果在较低载荷下,填充5%MoS_2可以更有效地降低PTFE/棉纤纤维织物复合材料的磨损率;在较高载荷下,填充10%石墨可以更有效地降低PTFE/棉纤纤维织物复合材料的磨损率。载荷为219.52 N时,5%MoS_2填充PTFE/棉纤纤维织物复合材料的磨损率由未填充的1.28×10~(-14) m~3/(N·m)降低到0.61×10~(-14) m~3/(N·m),降低了50%;10%石墨填充PTFE/棉纤纤维织物复合材料的磨损率由1.28×10~(-14) m~3/(N·m)降低到0.91×10~(-14) m~3/(N·m),降低了28%。结论石墨和MoS_2填充在摩擦过程中减轻了磨粒的嵌入和切削作用,阻碍了复合材料的磨损,提高了PTFE/棉纤纤维织物复合材料的耐磨性能。     

载流条件下铜-石墨复合材料摩擦学性能研究

在载流高速摩擦磨损试验机上进行试验,研究了不同电流和速度对铜-石墨复合材料摩擦系数和磨损率的影响,并对摩擦表面的形貌进行了观察和分析。结果表明:电流、速度是影响铜-石墨复合材料载流摩擦磨损性能的重要因素。在速度一定的条件下,随着电流增大,铜-石墨复合材料的摩擦系数减小,磨损率增大;在电流一定的条件下,材料的摩擦系数随速度的增大先升高后降低,磨损率随速度的增大先升高后降低,然后迅速增大,在速度为40 m/s时,材料的磨损机制出现了明显的变化。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.