7090/SiC_p复合材料的固溶工艺制度研究

研究了移动坩埚式喷射沉积制备的7090/SiCp复合材料的两种固溶热处理工艺对其组织和性能的影响。观察了材料挤压态、固溶态及时效后样品的微观组织及X射线衍射图谱。通过两种固溶制度的比较,表明经过挤压变形处理的移动坩埚式喷射沉积制备的7090/SiCp复合材料,经475℃×1h+120℃×24h处理后材料的最高抗拉强度仅有715MPa,而经450℃×3h+500℃×3h+120℃×18h热处理后复合材料达到峰时效,材料的最高抗拉强度可以达765MPa。     

单级固溶处理喷射沉积7090/SiCp的组织与性能

研究了固溶处理工艺对喷射沉积7090/SiCp铝基复合材料的显微组织和力学性能的影响.结果表明挤压态复合材料的基体合金中存在大量的第二相粒子;固溶处理后,晶粒发生不同程度的长大.在T6条件下,材料经470℃单级固溶处理后的布氏硬度值达到248 HB.对试样采用470℃×0.5 h(水淬)热处理,其抗拉强度可达到601.46 MPa,屈服强度为421.16 MPa.     

7075/SiCp复合材料时效组织与力学性能

研究了T6热处理对多层喷射共沉积制备的7075／SiCp复合材料组织和力学性能的影响。结果表明，材料经470℃固溶1h水淬后，120℃时效24h达到峰时效，材料的最高抗拉强度可达735MPa。     

热处理7090/SiCp铝基复合材料的组织与性能

研究单级固溶及峰值时效处理对多层喷射沉积7090／SICp复合材料显微组织及室温力学性能的影响,观察了挤压态、固溶及时效处理后的显微组织,并对其进行力学性能测试。结果表明：挤压态复合材料的晶粒均匀细小,基体合金中存在大量的第二相颗粒,为富铜相及MgZn2相;经过固溶处理后,复合材料的晶粒尺寸约为3μm,第二相颗粒明显减少,溶入基体合金中;采用475℃,1h固溶处理制度,其抗拉强度为610MPa：经过475℃,1h＋120℃,24h时效处理后,其抗拉强度可达765MPa。     

喷射沉积SiCp/7090Al复合材料固溶组织及力学性能

采用多层喷射共沉积技术制备了SiCp/7090Al复合材料锭坯,对其进行了热挤压变形,研究了固溶处理对复合材料显微组织及力学性能的影响.结果表明,挤压态SiCp/7090Al复合材料的基体合金中存在大量短棒状的MgZn2相及圆形的CuA12相颗粒,晶粒内部的MgZn2粒子长约200 nm,直径约60 nm;晶粒内的CuAl2相为直径40～420 nm的球形粒子,主要分布在晶界或近晶界区域.确定了最佳固溶温度为475 ℃,固溶时间为1 h.经过固溶处理后,析出相颗粒MgZn2及CuAl2粒子溶入到基体,复合材料棒材的力学性能为:σb＝610 MPa,δ＝2.0%.     

固溶处理对高强度铝合金组织和性能影响

观察了沉积态、挤压态、热处理后样品的显微组织,对经固溶处理的样品进行了力学性能测试。研究了不同固溶处理和不同挤压比对喷射成形7055超高强度铝合金的显微组织和性能的影响。结果表明:在475~480℃固溶1.5~2 h然后130℃时效24 h的材料性能最佳。热处理后的材料抗拉强度达到725 MPa,提高了5%;伸长率达到了13.0%,提高了40%。     

原位TiC颗粒对喷射沉积7093铝合金微观组织的影响

采用喷射沉积及原位反应喷射沉积方法制备7093铝合金及7093+TiC铝合金,研究试验合金420℃热挤压及不同固溶处理后的微观组织和力学性能。探索原位TiC颗粒对喷射沉积7093铝合金组织的影响。结果表明,原位TiC颗粒能够提高喷射沉积7093铝合金的再结晶温度10℃,当固溶温度达到490℃时,7093+TiC铝合金中的富Cu颗粒基本溶解,但并未出现过烧现象。采用450℃×3h+480℃×3h+120℃×24h的制度处理后,7093+TiC铝合金的抗拉强度达754 MPa,伸长率达7.1%。     

热处理对半固态挤压SiC_p/2024复合材料的影响

采用扫描电镜(SEM)、X射线衍射仪(XRD)、电子探针等研究了固溶处理对半固态挤压SiC_p/2024复合材料的组织和性能的影响。结果表明,SiCp/2024复合材料经过500℃×12h固溶和170℃×16h时效处理后,抗拉强度达到了478MPa,硬度(HV)为150,而在未热处理之前材料硬度(HV)仅为86,抗拉强度也只有350 MPa。     

喷射成形7055铝合金热处理工艺与力学性能的研究

主要研究了喷射成形7055铝合金经过反挤压成型以及热处理后的金相显微组织和力学性能.对挤压态合金进行固溶处理和时效处理后得到了时效硬化曲线并进行了力学性能测试.结果显示:480℃×2h的固溶制度为最佳固溶制度;通过测试硬度值确定最佳单级时效制度为120℃×18h,其硬度可达209HV.抗拉强度为692.12MPa,伸长率为3%.为了进一步提高该合金的伸长率,又对固溶处理件进行双级时效处理(120℃×3h 160℃×4h),其硬度为205HV,抗拉强度为683MPa,伸长率为9.5%.     

楔压加工对SiCp/7090铝基复合材料的影响

采用一种新型的楔压工艺对大尺寸多层喷射共沉积SiCp/7090复合材料进行致密化加工,研究了楔压加工对多层喷射沉积工艺制备的SiCp/7090复合材料组织及性能以及沉积坯与挤压坯密度的影响规律.研究表明,楔压过程中,在大的静水压力以及剪切应力的共同作用下,复合材料中孔洞被逐渐拉长闭合,致密化效果良好,压制后,SiC颗粒被明显破碎,其分布得到改善.致密化后的材料经过热处理后其横向强度σb达到540 MPa,压向强度σb达到325 MPa.     

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.