深冷处理对Cu-Zn合金微观力学性能的影响

用纳米力学测试系统测试经深冷处理前后Cu-Zn合金的微观力学性能,利用金相显微镜对深冷处理前后Cu-Zn合金的组织进行分析。在此基础上,探讨了深冷处理对Cu-Zn合金微观力学性能的影响。结果表明:深冷处理能增大Cu-Zn合金的硬度、弹性回复系数和硬弹比,有效提高了该合金的抗塑性变形能力。     

深冷处理对双金属带锯条基体用Rm80钢的影响

研究了深冷处理对Rm80钢力学与疲劳性能的影响。结果表明深冷处理使该钢的力学及疲劳性能普遍提高,尤其以第一次回火后深冷处理具有较好的综合效果。深冷处理过程中马氏体的分解、超微细碳化物的析出以及组织细化是该钢性能得以改善的主要原因。     

带有氮气回收深冷处理设备的设计

对深冷处理技术及传统的深冷处理设备进行了简单总结,在此基础上提出了一种带有液氮回收的深冷处理设备。采用翅片管式换热器作为该深冷设备的中间换热设备,液氮通过换热器管侧进行热交换,翅片侧通过风机提供一定流速的气流进行强制对流换热,利用热交换后的气流控制设备的温度,热交换后的氮气流出换热器进行回收利用。根据使用要求对换热器进行了设计计算,确定了换热器的结构及尺寸大小。采用经验公式对该换热器的压降进行了计算,对比了该设备与传统深冷设备的效率和经济性。     

深冷处理对镍基高温合金GH3030力学性能和组织的影响

研究了深冷处理对GH3030硬度、强度和显微组织的影响。研究发现,10 h的深冷处理使该材料的显微硬度提高20.54%。继续延长深冷处理时间,材料的显微硬度下降,到100 h时,材料的显微硬度下降13.51%。深冷处理对材料的抗拉强度变化影响不明显。     

深冷处理对超低温轧制2524铝合金板材组织及性能的影响

采用光学显微镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)和电子万能试验机等研究了深冷处理对超低温轧制2524铝合金轧制板材显微组织和力学性能的影响。结果表明，深冷处理后2524铝合金中第二相主要沿晶界分布，数量增多，主要为S-Al₂CuMg相和θ-Al₂Cu相。与轧制板材相比，深冷处理后板材的织构极密度均有提升，呈现先增加后降低的趋势，在深冷处理9 h时达到了峰值。经深冷处理6 h后板材的抗拉强度和伸长率分别为490 MPa和6.35%。同时该深冷条件下，试样的断裂模式主要表现为韧性断裂。     

循环深冷-热处理对镍基高温合金GH3030力学性能和组织的影响

将循环深冷-热处理工艺引入到GH3030高温合金中,研究了深冷处理次数对GH3030力学性能的影响。研究发现,通过多次深冷-热循环处理工艺处理与经过单次深冷处理相比,GH3030的硬度值随着深冷-热处理循环次数的增加而逐步变大并最终趋于稳定,该硬度值比单次深冷处理的稳定硬度提高30.06%,比原材料的硬度提高14.59%,而对材料的抗拉强度几乎没有影响。     

W6Mo5Cr4V2高速钢深冷处理工艺试验研究

采用正交试验方法研究了W6Mo5Cr4V2高速钢深冷处理工艺,分析部分深冷处理对材料力学性能的影响,并观察深冷处理前后金相显微组织变化。试验结果发现,高速钢深冷处理最优工艺条件为2次的深冷处理、缓慢冷却及缓慢升温液体法的深冷方式、200℃回火和4 h的浸泡时间。同时认为深冷处理次数对深冷处理对W6Mo5Cr4V2高速钢力学性能影响最显著,深冷处理方式其次。故在进行深冷处理时可适当多次深冷处理,但并不是越多越好。     

磁场深冷处理对合金钢力学性能的影响

对4Cr13、65Mn、60Si2Mn三种工业用钢分别进行了常规淬火、深冷处理和磁场深冷处理，并对经处理后的试样进行了力学性能测试。试验结果表明，深冷处理能提高钢的硬度、强度、冲击韧度和耐磨性，而磁场深冷处理的强韧化效果又明显超过常规深冷处理的。     

深冷处理对AZ31B镁合金焊接接头疲劳性能的影响

研究了深冷处理对镁合金焊接接头疲劳性能影响。采用TIG焊接AZ31B镁合金,在-160℃、保温12 h深冷工艺下对镁合金焊接接头进行深冷处理。测试未深冷组和深冷组镁合金焊接接头疲劳性能,用最小二乘法拟合实验数据得到S-N曲线,计算2×106循环次数下,未深冷接头疲劳性能为36.42 MPa,深冷接头疲劳性能为41.26 MPa,深冷处理后接头疲劳强度提高13.29%。用盲孔法分别测试未深冷和深冷后垂直焊缝不同位置的残余应力。结果表明:深冷处理后焊接残余应力下降;深冷处理后焊缝晶粒比未深冷焊缝晶粒明显细化。未深冷接头疲劳断口为解理断裂,深冷后接头疲劳断口为韧性断裂,说明深冷处理可提高焊接接头韧性。深冷处理可以提高镁合金焊接接头疲劳性能。     

深冷处理对黄铜电阻率的影响

利用电阻率测试仪测试了深冷处理前后黄铜在25～600℃的电阻率,并探讨了深冷处理对黄铜电阻率的影响.结果表明:深冷处理前后黄铜的电阻率均随温度的升高而增大,当温度低于300℃时,深冷处理后黄铜的电阻率大于深冷处理前的电阻率;高于300℃时,深冷处理后黄铜的电阻率小于深冷处理前的电阻率.     

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.