变形量对Cu-Cr-Zr合金连续加热时效动力学的影响

通过观察铜合金在连续加热过程中电阻率的变化,研究了不同变形鼍的Cu-Cr-Zr合金的连续加热时效动力学.结果表明:Cu-Cr-Zr合金等速加热时效时电阻率的变化量Ap与温度曲线随热速率的增加向右移动;Cu-Cr-Zr不同形变量合金连续加热时效时电阻率的变化量△ρ与温度关系曲线随形变量的增加向左移动.     

铜合金时效处理温度对析出过程的影响

通过测试Cu-Cr-Zr合金在等温加热过程中电阻率的变化,提出了一种计算相对电阻率减小值△γ的方法,并以△γ作为描述时效过程的参数,对该合金等温加热时效动力学进行了研究.结果表明,Cu-Cr-Zr合金在等温时效开始阶段,相对电阻率的变化量△γ急速增加,随着时效时间的增加,△γ,上升幅度逐渐变小,时效结束时△γ趋于稳定,且相对电阻率的变化量△γ的增加速率随等温时效温度升高呈现增加趋势;随等温时效温度升高,孕育时间呈现缩短趋势.在此基础上,建立了等温加热时效动力学图,其形状并未呈现常见的"C"形.     

B93合金的时效析出特性研究

对B93合金进行了X射线衍射物相分析及晶格常数的精确测量,定性地表征时效过程中MgZn2相的析出,并通过测试B93合金在等速加热和等温延时过程中电阻率的变化来模拟时效第二相粒子的析出过程.结果表明,等速加热时效时,由于不同温度下合金析出相的析出程度不同,电阻率随着温度的变化而变化;在同一温度保温时,随着时间的延长,电阻率减小,当析出完全后,电阻率保持在同一水平不再变化;而时效温度越高,电阻率越大,电阻率曲线下降的速率越快,到达水平值所需要的时间也就越短.同时,根据电阻率随温度变化曲线模拟出电阻率计算公式.     

变形量对Cu—Cr—Zr合金等温时效动力学的影响

采用在线电阻测试法研究经不同变形量的Cu-0.38Cr-0.12Zr合金的等温时效动力学.结果表明:等温时效动力学符合Avrami相变动力学经验方程;首次发现Cu-0.38Cr-0.12Zr合金的时效过程由两个析出过程组成,在大约340℃以下出现一个析出时效过程,在高于此温度时效时,将有两个过程发生,发生这两个过程的原因是Cu-Cr-Zr合金中在不同阶段有不同物质的析出;冷变形增加了材料内部的空位和位错密度,增大了时效动力学,使材料的电阻率随时效时间的增加而降低,最后趋于稳值,并且随变形量的增加,电阻率下降越快.     

Cu-0.38Cr-0.12Zr合金等温时效动力学研究

通过直接测定电阻率研究了Cu-0.38Cr-0.12Zr合金等温时效过程,其相对电阻率γ的变化量Δγ符合Avrami经验方程转化关系。合金经360℃时效90 min后,组织由α-Cu基体和Cu_5Zr相组成。随着时效时间的延长,Cu_5Zr相逐渐粗化,由面心立方结构转变为体心立方结构的Cu_4Zr相,并出现单质Cr相。经TEM分析确定Cr相形状为彼此相互连接的多个类似菱形的相,并存在周期性。     

热轧态Cu-Fe-P合金的相变动力学研究

通过对热轧态Cu-2.5％Fe-0.03％P-0.1％Zn合金时效过程中的导电率与析出相体积分数之间的关系研究了该舍金的相变动力学。以不同温度时效时的导电率试验数据可确定该合金的相变动力学方程的系数,从而描绘出不同温度时效时的相变动力学“S”曲线以及合金等温转变TTT曲线。     

7050铝合金在回归加热过程中的组织演变规律

采用差示扫描量热法(DSC)、高温X射线衍射(HTXRD)、透射电镜(TEM)观察、硬度测试以及电导率测试等手段,研究了不同的加热速率(340, 57, 4.3 ℃·min-1)对7050铝合金在回归加热过程中组织演变的影响。结果表明：在回归加热过程中,预时效态组织的GP区和η′相将发生回溶或依次转变为η′相和η相,而且回归加热速率对回溶和转变的温度产生显著影响,随加热速率提高,回溶和转变的温度升高。在一定的回归温度下,不同的加热速率使得合金在加热至回归温度时较预时效态具有不同的组织结构,从而影响合金在回归阶段发生不同的组织转变。本研究认为中等加热速率下,预时效态组织在加热至回归温度时所获得的组织结构最有利于回归阶段的组织转变。     

热轧态Cu-Ni-Si-Mg合金的时效动力学

对经过连铸连轧处理的Cu-Ni-Si-Mg合金进行时效,研究了时效温度和时效时间对该合金组织和性能的影响,并对该合金在不同温度下的时效动力学进行了分析。结果表明:合金在450℃时效2 h时能够获得较好的综合性能,其显微硬度和导电率分别为230 HV和35%IACS;通过对合金在时效过程中导电率的变化规律的分析,推导出合金在不同温度下时效的相变动力学方程和导电率方程,在此基础上做出了动力学"S"曲线和导电率方程曲线,该导电率方程与试验值吻合。     

7150 Al-Zn-Mg合金固态反应动力学参数的测定

采用差示扫描量热法（DSC）,在不同加热速率下研究7150 Al-Zn-Mg合金在水淬、自然时效和人工时效状态下的固态反应。DSC曲线上不同的放热和吸热峰对应着不同的固态反应阶段。随着加热速率的增加,各个峰位对应的温度也随之增加,表明这些固态反应是热力学活化和动力学控制的。通过测量不同时效时间下合金的硬度来评估合金的时效行为。通过分析DSC曲线各个峰位对应的热流,得到了合金固态反应的相变分数（Y）、相变速率（dY/dt）、相变函数（f（Y））和动力学参数（活化能Q、频率因子k0）。结果表明：所得到的这些动力学参数与已有文献所报道的结果吻合较好。     

Cu-3.2Ni-0.75Si-0.30Zn合金时效过程的动力学分析

通过研究时效过程中电阻率的变化规律 ,分析了Cu 3.2Ni 0 .75Si 0 .30Zn合金的时效析出特性及其动力学过程。结果表明 :低温时效时扩散作用是合金析出过程的主要控制因素 ,时效早期通过调幅分解形成溶质原子的富集区 ,然后在溶质富集区发生失稳有序化 ,最后生成δ Ni2 Si相 ;高温时效时相变驱动力成为主要控制因素 ,由于生成δ Ni2 Si相的驱动力较大 ,所以直接析出δ Ni2 Si相。结合透射电镜研究了合金时效过程中显微组织的变化 ,并得出了合金的时间—温度—转变曲线 (即TTT曲线 )。     

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.