低碳马氏体细晶粒钢的显微组织及耐磨性能

采用微合金化和控制轧制获得11～12级原始晶粒的细晶合金钢,研究了该合金钢的显微组织、力学性能及摩擦磨损性能.结果表明,通过适当的热处理可获得板条马氏体 残留奥氏体 弥散分布碳化物的显微组织;其抗拉强度为1600～1936 MPa、断面收缩率为25%～45%、伸长率为8%～14%、硬度为46～52 HRC、冲击韧度为55～103 J/cm2.在250 N载荷、0.84 m/s条件下,其磨损方式主要表现为磨料磨损和轻微的粘着磨损.     

马氏体/贝氏体双相细晶粒钢的组织与性能研究

对马氏体/贝氏体双相细晶粒钢的组织及性能进行了研究.结果表明,30SiMnCrMoVTi经950℃×30min 330℃×1min 220℃×40min处理后获得了马氏体 下贝氏体的双相组织,其抗拉强度达1736MPa,伸长率和断面收缩率分别为10.8%和43.3%,硬度为48.5HRC,冲击韧度为86.77J/cm2.     

20Si2Mn2CrNi钢锻后晶粒细化及强韧性提升工艺

研究了Si-Mn-Cr-Ni系低合金高强钢锻件在不同热处理工艺下的显微组织和力学性能。结果表明,试验钢经820℃正火后,锻件组织细化效果较好且分布均匀,再经920℃淬火和280℃低温回火后,其硬度为43.9 HRC,冲击吸收能量KV₂为82.6 J,抗拉强度为1513.35 MPa,屈服强度为1221.92 MPa,伸长率为14.65%,此时组织为回火板条马氏体且晶粒尺寸细小,晶粒度为8.3级,达到最佳的强韧性匹配,试验钢的综合力学性能最优。     

碳含量对ZGCr17Ni2马氏体不锈钢组织和力学性能的影响

采用光学显微镜、扫描电镜、洛氏硬度计、冲击等试验方法,研究了碳含量对ZGCr17Ni2马氏体不锈钢组织和力学性能的影响。结果表明:碳含量从0.17%增加至0.99%时,ZGCr17Ni2不锈钢显微组织由珠光体+马氏体+残余奥氏体+碳化物+δ铁素体转变为珠光体+马氏体+残余奥氏体+碳化物+莱氏体,且碳含量增加,莱氏体含量增大;硬度由HRC35提高至HRC50,冲击功则由45 J降至8 J。     

碳含量对ZG31Mn2Si组织和性能的影响北大核心CSCD

作为新型低合金耐磨钢,根据其硬度和冲击韧度,硅锰钢一定程度上可替代高锰钢,用作圆锥衬板材料,以提高衬板性能并降低成本。研究了ZG31Mn2Si在890℃正火预处理+890℃淬火+200℃回火的热处理条件下,含碳量在0.2%~0.55%之间时对其显微组织和力学性能(硬度和冲击韧度)的影响。结果表明:当合金的含碳量逐渐增加时,组织中的残余奥氏体量逐渐减少,板条马氏体中逐渐出现少量针状或片状马氏体;随含碳量增加,合金硬度逐渐提高,而冲击韧度整体呈下降趋势。ZG31Mn2Si碳含量为0.30%时,最大硬度值HRC 47,冲击韧度值33 J/cm2,综合性能最优。     

ZG28CrMn2VB钢的成分设计及热处理工艺研究

设计了低合金耐磨钢ZG28CrMn2VB的化学成分,并研究了热处理工艺对其力学性能和显微组织的影响。结果表明:当水冷淬火温度从850℃升高到910℃时,淬火后试样的硬度从31 HRC逐渐增加到37.5 HRC,冲击韧性从38.9 J·cm~(-2)降低到28.4 J·cm~(-2);890℃水淬+200℃回火后的试样具有最佳的力学性能,其显微组织是板条马氏体。在低应力冲击环境下,ZG28CrMn2VB钢具有优良的抗摩擦磨损性能。     

碳含量对ZG31Mn2Si组织和性能的影响

作为新型低合金耐磨钢,根据其硬度和冲击韧度,硅锰钢一定程度上可替代高锰钢,用作圆锥衬板材料,以提高衬板性能并降低成本。研究了ZG31Mn2Si在890℃正火预处理+890℃淬火+200℃回火的热处理条件下,含碳量在0.2%~0.55%之间时对其显微组织和力学性能(硬度和冲击韧度)的影响。结果表明:当合金的含碳量逐渐增加时,组织中的残余奥氏体量逐渐减少,板条马氏体中逐渐出现少量针状或片状马氏体;随含碳量增加,合金硬度逐渐提高,而冲击韧度整体呈下降趋势。ZG31Mn2Si碳含量为0.30%时,最大硬度值HRC 47,冲击韧度值33 J/cm2,综合性能最优。     

Y_2Ti_2O_7纳米颗粒对CLAM钢组织与性能的影响

为了提高CLAM钢的力学性能,采用传统熔炼法,对CLAM钢添加Y_2Ti_2O_7纳米颗粒。采用光学显微镜、扫描电镜、透射电镜观察和拉伸、冲击试验等方法,对比研究了轧态和回火态下未添加和添加Y_2Ti_2O_7颗粒的CLAM钢的显微组织和力学性能。结果表明:轧制态CLAM钢的组织为马氏体和残留奥氏体,回火态CLAM钢的组织为板条马氏体。在回火态,与未添加Y_2Ti_2O_7相比,添加0. 5%(质量分数) Y_2Ti_2O_7的CLAM钢的晶粒尺寸减小了46. 2%,抗拉强度由655 MPa提高到了673 MPa,冲击吸收能量由195 J增加到了220 J,硬度由15. 38 HRC升高到了17. 16 HRC。     

高硼低碳钛氮耐磨铸造合金的试验研究

为提高金属材料的耐磨性,在普通低碳钢中加入B(2.5~4.0)%和Ti、N(0.20~0.40)%,获得了大量具有高硬度硼化物的铸造合金,并对其显微组织进行了观察和XRD分析。结果表明:铸造合金的铸态组织比较细密,由铁素体+珠光体+Fe2B组成,Fe2B呈连续网状沿晶界分布,铁素体呈不规则块状分布在硼化物周围,珠光体呈片层状分布在硼化物和铁素体之间;经980℃×2h+250℃×4h淬回火热处理后,铁素体和珠光体全部转变为强韧性均好的板条马氏体组织,Fe2B局部出现断网现象,仍呈网状分布;少量Ti、N元素的加入可细化奥氏体晶粒,显著改善Fe2B韧性。经测试,热处理铸造合金硬度≥60.2 HRC,冲击韧性≥25.5 J/cm2,耐磨性相对40Gr钢提高了2.5倍。     

低碳硅锰钢奥氏体区形变对贝氏体组织及力学性能影响

以低碳硅锰钢为研究对象,采用QPB与奥氏体形变+QPB两种工艺,利用Gleeble-3500热模拟试验机、SEM以及拉伸试验机等对奥氏体形变对其组织及力学性能的影响进行研究。结果表明:试样经奥氏体形变之后,显微组织由粗大板条贝氏体、块状M/A岛以及马氏体演变成较细板条贝氏体以及M/A岛,块状马氏体数量减少,显微组织得到明显细化;抗拉强度由1038 MPa降到1012 MPa,伸长率由11.8%提高到13.9%,强塑积得到提高,综合力学性能得到改善。     

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.