Ni3Al基单晶合金IC6sx的表面再结晶

对Ni3Al基单晶合金IC6sx的表面进行吹砂变形处理;再在800-1260 ℃热暴露1-10 h,采用OM,SEM和EPM研究了IC6sx合金的再结晶行为.结果表明,合金再结晶开始形核的温度约1000 ℃,一次再结晶完成的温度为1200-1210 ℃.在1200-1240 ℃热暴露时的再结晶层厚度约为10 μm,而在1260 ℃热暴露时增长到约23 μm.再结晶在枝晶干长大的速度明显小于枝晶间,再结晶层和基体的枝晶干之间观察到一种由粗大条状γ′相和γ γ′相构成的胞状转变结构,这是由于枝晶干中粗大的γ′相阻碍再结晶向基体内生长形成的.     

单晶高温合金再结晶形核条件及长大机制

对DD6单晶高温合金进行表面压痕处理,然后在不同温度(1220、1270和1310℃)热处理2h,研究合金再结晶的形核和长大行为.结果表明:γ'相溶解是再结晶的必要条件;再结晶晶粒以外,产生大量的亚晶界,离压痕中心越近,亚晶界密度越大,亚晶聚合粗化是再结晶的形核和长大机制.在γ'相溶解温度以上,γ'相对再结晶的形核和长大无明显影响.     

第三代新型镍基单晶高温合金再结晶行为研究

对第三代新型镍基单晶高温合金试样表面施加载荷处理,并在1 100~1 330℃保温4 h,研究合金铸态和热处理温度及载荷对再结晶行为影响。结果表明,DD9-X合金在1 100℃和1 200℃处理下加载区域附近并未发生明显的再结晶现象;1 300℃处理加载区域形成了枝晶状的再结晶晶粒;1 330℃处理试样的加载区域形成了等轴状再结晶晶粒,证实了γ′相粒子的溶解是再结晶产生的必要条件。由于铸态合金含有粗大γ′相以及γ+γ′共晶相组织,同等条件下,合金铸态试样的表面再结晶深度和区域面积均小于热处理态。随着载荷大小的增加,DD9-X合金试样的再结晶深度和区域面积都明显增加。     

DZ4镍基高温合金的再结晶

用扫描电镜和X射线衍射方法研究了DZ4合金喷丸试样在不完全固溶和固溶热处理过程中的再结晶行为．在保温2h条件下,DZ4镍基高温合金喷丸层在1000℃可发生再结晶;在不完全固溶热处理中,再结晶以胞状形式发生;在固溶热处理中,再结晶以晶粒形式发生;γ相对再结晶晶界迁移具有阻碍作用;再结晶速率和再结晶层厚度主要取决于热处理温度,保温时间影响不显著．拉伸试样的金相观察表明,DZ4合金在1220℃保温2h条件下再结晶的临界变形大约为0．9％;再结晶晶粒优先在拉伸试样表面形核．     

Ti-5553合金高温变形时动态再结晶行为

采用热压缩试验方法,对Ti-5553钛合金的动态再结晶行为进行研究。结果表明,在温度800～860℃、应变速率0.01～10s-1的范围内,Ti-5553合金在高温、低应变速率变形时,晶界弓出形核是其主要的动态再结晶形核机制;在低温、高应变速率、大变形量变形时,位错塞积形核是主要的动态再结晶形核机制。在非均匀变形的条件下材料产生绝热剪切现象,其形核主要以亚晶吞并长大形核机制进行。     

加工参数对铸态AZ31B镁合金热变形行为及组织演变的影响

借助热压缩实验研究了变形温度、应变速率和变形量对铸态AZ31B镁合金热变形行为及组织演变的影响规律。结果表明:(1)峰值应力随着应变速率的降低和温度的升高而减小,主要的形核机制为晶界弓出形核、亚晶旋转形核、孪生诱发形核,以及连续再结晶;(2)低于400℃变形时,温度的升高有利于再结晶的发生及晶粒细化;高于400℃时,晶粒尺寸开始迅速增大;(3)在小于等于400℃变形时,低速率0.1 s~(-1)更有利于再结晶晶粒细化;当变形温度高于400℃时,中速率1 s~(-1)更有利于再结晶晶粒细化;(4)高温低速率变形时,变形量主要影响晶粒尺寸,而高温高速率变形时,变形量主要影响动态再结晶程度。     

冷轧FeCrCuMnNi多相高熵合金退火组织和织构形成的评价（英文）

研究冷轧态FeCrCuMnNi多相高熵合金经不同退火处理后显微组织和织构的变化。样品经不同温度和不同时间热处理后进行不同的检测和表征,包括X射线衍射和扫描电镜-电子背散射衍射分析。结果显示,FCC1相具有较低的熔点,再结晶温度较低,时间较短,且应变较大。此外,与FCC2相比较,粒子激发形核对FCC1相的再结晶更有效。在BCC颗粒周围形成了大量FCC1晶核。FCC2的形核发生在800℃,大部分在晶界和不均匀处形核。此温度下,FCC1相已经完全再结晶。退火过程导致轧制组织的消除,而再结晶样品中的主要成分仍然是黄铜。提高退火温度和延长退火时间导致立方织构的形成,立方织构是低堆垛层错能材料再结晶的主要成分。此外,由于退火孪晶的形成,再结晶过程中形成了D和Rt-Co成分。     

合金状态对单晶高温合金DD6再结晶的影响

对单晶高温合金DD6进行表面吹砂处理,然后在1100～1250℃加热4h,研究其铸态与标准热处理状态的表面再结晶行为。结果表明:当加热温度为1200℃时,铸态合金出现等轴再结晶晶粒;而加热温度为1150℃时,热处理态合金出现等轴再结晶晶粒,铸态与热处理态合金的再结晶是由胞状再结晶晶粒和等轴再结晶晶粒组成的;随着加热温度的升高,等轴再结晶晶粒逐渐长大,胞状再结晶晶粒逐渐减少,胞状再结晶内部粗大的γ′相由长条状向颗粒状转变。由于铸态合金含有一定数量的粗大γ′相以及γ+γ′共晶组织,在相同的条件下,铸态合金的再结晶倾向小于热处理态合金的。     

热挤压态FGH95合金的动态再结晶机制研究

针对热挤压态FGH95合金进行变形温度为1050~1120 ℃、变形量为50%和70%、应变速率为10?4~1 s?1的热压缩试验,研究该合金动态再结晶（DRX）的组织演变和形核机制。结果表明:提高变形温度和降低应变速率可以促进小角度晶界向大角度晶界迁移,有利于动态再结晶晶粒的长大;变形温度和变形量对热挤压态FGH95合金的动态再结晶机理的影响不明显,而应变速率对动态再结晶机制影响较大;随着应变速率的增加,热挤压态FGH95合金由不连续动态再结晶机制逐渐转变为连续动态再结晶机制;热挤压态FGH95合金的动态再结晶以不连续动态再结晶形核机制为主,以连续动态再结晶形核机制为辅;在1050 ℃、1 s?1变形条件下,热挤压态FGH95合金发生连续动态再结晶形核。     

Al－Mg－Li系01420合金的再结晶

对Ａｌ－Ｍｇ－Ｌｉ系０１４２０合金的再结晶温度和再结晶形核机制进行了研究。结果表明：其再结晶的开始温度为４００℃，终了温度为５００℃；再结晶温度较高的原因是ＺｒＡｌ３为一种有效的再结晶抑制剂，可对位错和亚晶界起钉扎作用；在再结晶过程中有两种形核机制即亚晶聚合和亚晶长大。     

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.