退火处理对超细晶Cu-Cr合金组织和性能的影响

对Cu-0．4Cr合金进行ECAP（等通道转角挤压）8道次的挤压，得到晶粒尺寸为500nm的等轴晶组织，然后在电阻炉内进行退火试验，通过对ECAP细晶的铜铬合金在473～873K退火1h，分析合金的组织和性能，研究该合金的硬度和导电性能。研究发现，弥散的Cr可以有效地阻止合金的晶粒长大；723K退火后，Cu-0．4Cr合金的电导率和硬度分别可达80．3％IACS和210．9HV，并有较好的综合性能。     

等径角挤压工艺对固溶状态CuCrZr合金性能的影响

研究了等径角挤压工艺(ECAP)对固溶态CuCrZr合金性能的影响.结果表明,随着挤压道次的增加,合金的硬度迅速上升,导电率略有下降.时效前经ECAP处理可以加速时效初期第二相的析出,使合金的性能以较快的幅度上升.ECAP六道次试样400℃时效1 h,导电率和硬度分别为81.1%IACS和200 HV30.     

ECAP及后续退火对Cu-Mg合金组织与性能的影响

采用等通道转角挤压(ECAP)和后续热处理对高铁接触导线用铜镁合金进行微观组织调控以获得优良的综合性能。结果表明:Cu-0.2%Mg(质量分数)和Cu-0.4%Mg合金在200℃下经多道次ECAP加工后,其晶粒组织明显细化,微观硬度和抗拉强度提高明显,同时仍保持了良好的导电率和伸长率。ECAP加工后Cu-Mg合金经不同温度退火后,其力学性能有较明显的下降,而导电率和伸长率有所提高。与Cu-0.2%Mg合金相比,Cu-0.4%Mg合金具有更好的抗高温软化能力。     

微量铪对铜及铜铬合金组织及性能的影响

采用真空熔炼铸造制备了Cu-0.15Hf、Cu-0.4Hf和Cu-0.6Cr-0.15Hf合金铸锭,随后通过热轧-固溶-冷轧-时效的工艺对合金进行形变热处理,测试了各工艺条件下的力学和导电性能。利用金相显微镜、扫描电子显微镜、透射电子显微镜研究了Cu-Hf和Cu-CrHf合金在各工艺阶段的组织演变以及时效析出相的形貌和结构。结果显示:Cu-0.15Hf、Cu-0.4Hf合金耐热温度均大于450℃,Cu-0.4Hf合金导电率可达80%IACS,硬度达160 HV0.2以上;Cu-0.6Cr-0.15Hf合金的耐热温度高于550℃,导电率可达80%IACS,硬度可达190 HV0.2以上。Cu-0.4Hf和Cu-0.6Cr-0.15Hf合金时效后的样品进行TEM观察,在Cu-0.4Hf合金中发现了大小约为20 nm的细小短棒状并且弥散分布的析出相,经过标定为面心立方Hf;同样地,在Cu-0.6Cr-0.15Hf合金中发现了大小差不多的短棒状Hf相,另外还发现了大量更为细小的咖啡豆状Cr相。     

形变热处理对Cu-Ti-Fe-Sn合金组织与性能的影响

利用真空熔炼法制备了Cu-3Ti-0.2Fe-1Sn合金,通过均匀化退火、固溶+冷轧(变形量分别为40%、60%、80%)+450 ℃时效处理,研究了形变热处理对Cu-3Ti-0.2Fe-1Sn合金显微组织、导电率及硬度的影响。结果表明:真空熔炼制得的 Cu-3Ti-0.2Fe-1Sn合金铸态组织中含有大量的枝状晶组织,经固溶处理后组织中出现了晶粒长大;铸态合金的硬度和导电率分别为178.1 HV和10.85%IACS,固溶处理后硬度和导电率都相应降低,分别为102.7 HV和4.58%IACS。经过冷变形和时效处理后Cu-3Ti-0.2Fe-1Sn合金硬度明显提高,变形量为60%时,时效480 min时硬度达到峰值,合金硬度为310.2 HV,此时合金的导电率为18.59%IACS。     

不同变形量对Cu-2Ag合金组织和性能的影响北大核心CSCD

总变形量一定的前提下,采用不同道次、不同变形量对Cu-2Ag合金棒材进行轧制变形,研究了不同变形工艺对Cu-2Ag合金微观组织结构和导电性能、力学性能的影响。结果表明,总变形量一定时,各道次变形量的分配对合金性能的影响不同,导电率和硬度分别为:工艺1,82.75%IACS、170.34 HV;工艺2,83.62%IACS、174.82 HV;工艺3,82.72%IACS、180.26 HV。实验条件下,第1道次轧制变形量越大(60%),合金的综合性能更优。轧制前合金的微观组织以交错分布的网状枝晶形态为主;轧制变形后,枝晶出现不同程度的变形,这是导致合金性能不同的主要原因。平行于轧制方向的微观组织以连续排列的“鱼骨”状枝晶形态为主;轧制变形后,枝晶间距增加。试验范围内,采用工艺3变形后,合金的硬导积达到0.989,综合性能较好。     

Cu-Ag-Cr合金时效析出行为研究

研究了时效参数和变形量对Cu-0.1Ag-0.61Cr合金性能的影响。结果表明:合金经980℃×20 min固溶后,在480℃时效1 h可获得较高的导电率和硬度。时效前对合金加以冷变形可以显著提高其显微硬度,合金经60%变形后在480℃时效30 min时,峰值硬度可达165.13 HV,导电率可达83%IACS,而固溶后直接时效分别仅为153.46 HV和77.63%IACS。与Cu-0.1Ag-0.46Cr合金相比其显微硬度有较大提高而导电率降低很少。     

上引连铸-连续挤压技术制备Cu-Cr-Zr合金的组织与性能EI北大核心CSCD

采用上引连铸-连续挤压技术制备Cu-0.88Cr-0.14Zr(质量分数)合金,并对挤压后的棒材进行不同制度的时效处理。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、电子背散射技术(EBSD)等分析测试手段研究合金经不同工艺/制度处理后的组织与性能的变化。结果表明:上引连铸Cu-Cr-Zr合金棒坯在连续挤压过程中发生了剧烈的剪切变形和动态时效,晶粒明显细化,析出尺寸为15~20 nm的Cr相,与铸态相比,挤压态合金的导电率与硬度分别增加了28.6%IACS、49.6 HV。确定了挤压态合金杆材经(925℃,12 h)均匀化退火和(1000℃,1 h)固溶处理后的峰时效制度是(475℃, 3 h),此时基体中析出了平均晶粒尺寸为2.6 nm的Cr相,合金的导电率和硬度分别可达73%IACS、155 HV。     

冷轧Cu-15Cr原位复合材料组织和性能研究

经冷轧变形和中间退火制备了Cu-15Cr形变原位纤维增强复合薄板材料。用SEM、拉伸试验机和电阻率测试仪研究了变形量及退火温度对Cr纤维形貌、合金强度及导电性能的影响。结果表明:随合金变形量的增加,Cr纤维逐渐变薄、变宽,纤维间距逐渐减小,材料的抗拉强度和导电率都逐渐增大。退火温度升高,材料抗拉强度随之降低,导电率先升高后降低,退火温度为550℃时,导电率峰值为84.4%IACS;退火温度升高,Cr纤维依次发生球化,球化加剧、纤维断裂。最终变形量时,材料达到较好的综合性能匹配,退火前抗拉强度和导电率为694 MPa和78%IACS;500℃退火后抗拉强度和导电率为570 MPa和83%IACS。     

Cu-0.81Cr-0.12Zr-0.05La-0.05Y合金形变与热处理工艺优化

对稀土微合金化Cu-0.81Cr-0.12Zr-0.05La-0.05Y合金的形变与热处理工艺进行了研究。结果表明,优化加工工艺为铸锭经1193 K温度均匀化退火60 min后热轧,然后于1223 K温度固溶处理60 min后快淬至室温进行应变为60%的冷变形处理,最后再于773 K温度时效60 min。经过这样处理的试样,具有良好的综合性能,其显微硬度和导电率分别达186 HV0.1和81%IACS。试样未经冷变形处理,显微硬度和导电率则分别为140 HV0.1和80%IACS,相比之下,时效前对试样施以20%~80%应变的冷变形,可明显提高合金力学性能达20 HV0.1以上。     

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.