力作用方式对定向CuAl合金马氏体相变的影响

采用真空熔炼、氩气保护下拉式连续定向凝固方法制备不同取向马氏体Cu-12%Al(质量分数)合金线材。通过测试线坯拉伸和压缩力学性能,研究了力的作用方式对定向CuAl合金马氏体相变和力学性能的影响,并分析变形前后线坯的物相。结果表明:马氏体母相取向为[001]的线坯拉伸变形和压缩变形真应变分别为24.4%和14.7%,相应断口表现为韧性断裂和解理断裂;马氏体母相取向为[110]的线坯拉伸变形和压缩变形真应变分别为0.09和0.809,相应断口表现为准解理断裂和韧性断裂。取向为[001]线坯拉伸变形或取向为[110]线坯压缩变形均会发生由β1′马氏体转变为β1′马氏体,转变机制为Bain转变;取向为[110]线坯拉伸变形或取向为[001]线坯压缩变形均会发生由β1′马氏体转变为β1′马氏体。取向为[110]线坯压缩变形时会发生单滑移或者双滑移塑性变形,具有较好的塑性变形能力。     

一种镍基第三代单晶高温合金的横向拉伸性能

在760℃到1100℃条件下,研究了一种镍基第三代单晶高温合金的横向拉伸性能。采用光学显微镜(OM)、场发射扫描电子显微镜(FESEM)与扫描透射电子显微镜(STEM)观察了合金的显微组织与断口形貌。结果表明：随着温度的升高,合金的拉伸强度降低,而拉伸延伸率增加。在760℃与850℃条件下的拉伸断裂均为类解理断裂。在980℃,1070℃和1100℃条件下,试样断口出现了反映凝固方向的枝晶形貌特征,且随着温度的升高枝晶形貌在断口上的面积增加。在980℃条件下,拉伸断裂为类解理断裂与韧窝断裂的混合断裂。在1070℃与1100℃条件下,拉伸断裂均为韧窝断裂。随着温度的升高,塑性变形过程中开动了更多滑移系,导致形成了不同的位错形貌。760℃拉伸,合金中出现了高密度大致平行分布的a/2<110>位错;980℃拉伸,合金中出现了位错缠结;1100℃拉伸,合金中形成了位错网络。     

熔体过热处理对Al-4.7%Cu合金定向凝固力学性能及晶体取向的影响

在熔体过热温度Ts分别为750、850、950、1050℃时,研究熔体过热温度对Al-4.7%Cu合金定向凝固组织及力学性能的影响,利用综合热分析仪测定Al-4.7%Cu合金熔体结构特征及变化过程,用扫描电镜观察断口形貌。结果表明,定向凝固试样力学性能与非定向凝固的相比,强度提高60%,断后伸长率提高近1倍。断口形貌观察表明,富Cu相明显减少,韧窝数量显著增加。随熔体过热温度提高及过热时间延长,试样强度及塑性提高,随低温保持时间延长,试样强度及塑性变差。Al-4.7%Cu合金枝晶沿择优方向<100>生长,且随熔体过热温度提高,(100)晶面衍射强度减弱,表明晶面取向产生分支。Al-4.7%Cu合金过热处理会使熔体结构(即团簇结构)发生一定变化。     

熔体过热温度对Al-4.7%Cu合金定向凝固组织和性能的影响

在温度梯度和抽拉速率一定的条件下,研究熔体过热温度Ts对Al-4.7%Cu合金定向凝固组织及力学性能的影响,利用综合热分析仪测定Al-4.7%Cu合金熔体结构特征及变化过程。试验结果表明:熔体过热温度对Al-4.7%Cu合金定向凝固组织及力学性能有显著影响,经过1 050℃过热处理的一次枝晶间距1λ比在750℃无过热直接定向凝固的减小了35%左右,抗拉强度提高了近30%,伸长率提高了近40%;熔体过热处理改变了熔体的结构状态,从而影响了最终组织及性能;通过熔体过热处理的Al-4.7%Cu合金,其富Cu相明显减少,断口韧窝数量显著增加。     

Cu-12%Al铝青铜线材的连续定向凝固制备

采用真空熔炼、氩气保护下拉式连续定向凝固方法制备了Cu-12％Al（质量分数）合金线材,研究了工艺参数对凝固成形过程的影响,分析了连续定向凝固线材的组织性能．结果表明：当熔体温度1250℃、下拉速度9mm／min、冷却水量900L／h时,可以连续稳定成形直径6mm,表面较光滑、具有单品组织的Cu-12％Al合金线材,其延伸率达到19．7％,弹性模量达到167．9GPa,电导率达到22．23％（IACS）,具有优良的综合性能．     

熔体过热处理对Cu-9Al-4Fe合金组织及高温力学性能影响

通过熔体过热处理方法,限定其它因素保持不变的情况下,研究了不同熔体过热温度对Cu-9Al-4Fe铝青铜合金(QAl9-4)的凝固组织及其高温力学性能的影响。结果表明:经熔体过热处理后的铝青铜合金凝固组织晶粒尺寸明显细化、形貌等轴化;高温超塑性能得到改善,800℃下初始最大拉伸屈服应力降低约28%,最大伸长率δ提高了约36%;600℃下其稳态蠕变速率和蠕变变形量明显降低,抗蠕变能力得到有效的提高。     

高能超声对Al-20Si合金组织和力学性能的影响

采用高能超声波对Al-20Si合金进行熔体处理,研究超声波处理对Al-20Si合金微观组织形貌及其力学性能的影响。结果表明,在660℃温度下,对Al-20Si合金熔体进行高能超声波处理,可以使Al-20Si合金的初晶硅形貌由粗大的板片状逐渐变成细小的球状颗粒,圆整度高,分布均匀,并且使其抗拉强度和伸长率提高。通过对合金拉伸断口形貌的观察,发现在经过超声处理的Al-20Si合金断口上有较多的撕裂带和韧窝,表现为脆性断裂和韧性断裂的混合型断口。     

区熔式定向凝固技术对7075铝合金微观组织和硬度的影响研究

采用Bridgman定向凝固系统对7075铝合金进行区熔式定向凝固试验,研究了感应加热温度(887～998℃)、拉伸速率(20～50μm/s)对凝固组织及硬度的影响。结果表明,7075铝合金定向凝固后,组织由原始枝晶形貌转变为等轴或近等轴柱状晶;当感应加热温度998℃且拉伸速率40μm/s时,得到的柱状晶形貌稳定,尺寸均匀,硬度最高。在参数范围内拟合的感应加热温度与试样硬度的线性关系式为HB=0.055T+15.5(T为温度)。     

锌铝合金热型连铸定向凝固的组织和性能

热型连铸锌铝合金线材定向凝固实验研究结果表明 :热型连铸锌铝合金线材显微组织为定向生长的平行柱状枝晶。共晶合金ZA5共晶的枝晶都由多层片状β和η两相构成 ,过共晶合金的组织为先共晶相枝晶和枝晶间共晶 ,与普通铸造材料相比 ,抗拉强度和硬度显著提高 ,但伸长率有所下降。从ZA5到ZA12、ZA2 2和ZA2 7,强度依次递升 ,其中ZA2 7的综合力学性能最佳。退火可使枝晶偏析减少 ,虽然强度略有降低 ,但塑性可得到改善     

锌侣合金热型连铸定向凝固的组织和性能

热型连铸锌铝合金线材定向凝固实验研究结果表明：热型连铸锌铝合金线材显微组织为定向生长的平行柱状枝晶。共晶合金ZA5共晶的枝晶都由多层片状β和η两相构成,过共晶合金的组织为先共晶相枝晶和枝晶间共晶,与普通铸造材料相比,抗拉强度和硬度显著提高,但伸长率有所下降。从ZA5到ZA12、ZA22和ZA27,强度依次递升,其中ZA27的综合力学性能最佳。退火可使枝晶偏析减少,虽然强度略有降低,但塑性可得到改善。     

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).     

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.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。