In order to evaluate the performance of the highly heat-resistant Al11Ce3 phase during the Additive Friction Stir Deposition (AFSD) process and to provide a basis for its subsequent introduction into other alloying systems by microalloying for AFSD processing, this study prepared AFSD-Al-Ce alloy deposits with an average layer height of about 2.8 mm and a layer number of 14 using the AFSD technique. The Al11Ce3 phase was investigated by comparing the microstructural evolution of the raw material, the as-deposited state samples, and the property strengthening mechanism. In the AFSD process, dynamic recrystallization leads to grain refinement rate of about 50.7 %, while the unprecipitated dissolved second phase (Al11Ce3 phase) is dispersed on the aluminum matrix by physical shear fragmentation (size reduction of about 40.3 %). Moreover, the dislocation interaction with Al11Ce3 phase was enhanced, and the dislocation multiplication was significant, and the dislocation strengthening effect was enhanced by about 72.7 %. However, the load transfer and reinforcement were substantially weakened due to the fragmentation of the large-size Al11Ce3 phase, leading to a decrease in the yield strength by about 8.7 %. This fragmentation also reduced the material's stiffness, resulting in a decrease in the modulus of elasticity by about 15.1 %. Further fragmentation of the Al11Ce3 phase reduced the number of primary cracks in the AFSD samples. In addition, on the one hand, the increase in dislocation density during plastic deformation leads to increased work-hardening of the material. On the other hand, the dispersed small-sized Al11Ce3 phase is capable of dispersing the stresses as well as withstanding higher localized stresses during tensile processes, delaying the onset of necking. The ultimate tensile strength and elongation at break of the AFSD samples were about 140.2 MPa and 15.1 %, respectively, which were about 11.7 % and 122.1 % higher than those of the AFSD raw material samples. In addition, this process results in the enhancement of the texture intensity and a change in the texture type from recrystallized to deformed. Based on this, it is foreseen that Ce will play an important role in the AFSD process when introduced as a microalloying element in other aluminum-based materials by stabilizing the microstructure and enhancing its interaction with dislocations.

Additive friction stir deposition (AFSD) additive manufacturing is a highly promising approach in solid-phase additive manufacturing. However, thermal input during the process can lead to dissolution of the reinforcing phase and abnormal grain growth during subsequent heat treatment. In this study, a hollow tool with tear-droplike projections (AFSD-P sample) was used to reduce heat input and mitigate the effects on grain coarsening and the dissolution of precipitated phases. Additionally, a strategy is proposed to suppress grain growth in the AFSD process and induce nanoparticle precipitation to inhibit recrystallization during T6 heat treatment by using Al-Ce alloys enhanced with rare-earth Sc through microalloying as the deposited material. It was shown that the ultimate tensile strength of the alloy samples machined by a flat-head hollow tool (AFSD samples, with an average grain size of about 4.2 mu m and an average particle size of the precipitated phase of about 87.9 nm) was about 154.6 MPa, the yield strength was about 58.4 MPa, and the elongation was about 23.3 %. On the other hand, the ultimate tensile strength of the AFSD-P sample (with an average grain size of only about 1.9 mu m and an average particle size of the precipitated phase of about 62.1 nm) was about 184.1 MPa, the yield strength was about 119.1 MPa, and the elongation was about 10.1 %. The increase in yield strength is mainly attributed to the reduced heat input from the hollow tool with tear-drop-like projections, which helps maintain microstructural stability, as well as the significant increase in overall yield strength due to heterogeneous deformation-induced strengthening (HDI). The average size of the microstructure of the samples before and after T6 heat treatment was about 4.2 mu m and 5.7 mu m, respectively. The heat-resistant nano-precipitated phases suppressed the abnormal growth of grains during heat treatment, resulting in an ultimate tensile strength of about 234.4 MPa, a yield strength of about 201.9 MPa, and an elongation of about 9.3 %. After T6 heat treatment, the average particle size of the precipitated bulk Al3Sc phase is only about 2 nm. Precipitation strengthening is the main contributor to the improved mechanical properties of the AFSD-T6 samples in this study.

A novel additive manufacturing dedicated Al-Zn-Mg-Si-Sc-Zr alloy is designed in this work, and its formability during selective laser melting (SLM) is investigated. Adding 3 % Si to the Al-Zn-Mg alloy leads to a refined microstructure and significant enhancement of hot-cracking resistance. By means of SEM, TEM and EBSD analysis some aspects of the alloy microstructure in as-built and thermal-treated states are discussed. Unlike traditional Al-Zn-Mg alloys, the main strengthening phase in the Al-Zn-Mg-Si-Sc-Zr alloy is Mg2Si, which forms a cellular structure and contributes to the favorable mechanical properties of the as-printed alloy. The as-built alloy exhibits a hardness of 138 HV, ultimate tensile strength (UTS) of 383 MPa, and elongation of 9.5 %. After solution and aging treatment, the UTS decreases to approximately 341-349 MPa, while the elongation increases to 17.6 %. However, with direct multistage aging treatment, the UTS can be increased to 409 MPa, albeit with a reduced elongation of 0.6-1.6 %. The variations in mechanical properties are attributed to the morphology of the Mg2Si phase and its coherent relationship with the Al matrix under different heat treatment processes.

The influence of Ga and In on the microstructure and electrochemical performance of a Zn-Al alloy was investigated. It was found that the microstructure of the Zn-Al sacrificial anode can be significantly refined by Ga and In, but excess Ga or In leads to segregation. Electrochemical tests show that Zn-0.5Al-0.07 Ga and Zn-0.5Al-0.1In have the most negative OCPs, the corrosion products of which can easily flake off from the corroded surface, showing the good performance of cathodic protection. A small amount of Ga and In contribute to the corrosion of the Zn-Al alloy; however, excess Ga or In can improve the corrosion resistance of the alloy by refining the grains and making the surface of the oxide film form quickly.

As the most widely used binder for cemented carbide, cobalt has some problems, such as resource scarcity, high cost, and WC-Co cemented carbide poor corrosion resistance. Considering the production costs and performance improvement, iron and nickel, instead of cobalt, were used to form a composite binder, with which ultrafine cemented carbide was prepared, and the relationships between its microscopic structure and mechanics as well as corrosion resistance and wear resistance were studied. The results show that the increase in Fe/Ni mass fraction ratio in the binder makes alloy WC grains refined and the distribution of binder uneven,and thus the hardness and anti-bending strength of alloys are increased and decreased, respectively. The corrosion resistance of alloys in neutral NaCl solutions was evaluated by polarization curve tests and immersion experiments. The addition of Ni to the binder improves the alloy corrosion resistance, which is attributed to the passivation characteristics of Ni and the formation of films promoting corrosion product. The friction coefficient and wear rate of cemented carbide are negatively correlated with Fe/Ni mass ratio. The improvement in alloy wear resistance is mainly due to the strength enhancement of binder phase and the hardness improvement of alloy caused by WC grain refinement.

During the material preparation process, the magnetic field can act with high intensity energy on the material without contact and affect its microstructure and properties. This non-contact processing method, which can change the microstructure and properties of material without affecting the shape and size of products, has become an important technical means to develop new materials and optimize the properties of materials. It has been widely used in scientific research and industrial production. In recent years, the magnetic field assisted processing of difficult-to-deform materials or improving the performance of complex and precision parts has been rapidly and widely concerned by scholars at home and abroad. This paper reviews the research progress of magnetic field regulating the microstructure, and properties of solid metal materials. The effects of magnetic field-assisted heat treatment, magnetic field assisted stretching, and magnetic field independent treatment on the microstructure and properties of solid metal materials are introduced. The mechanism of the magnetic field effect on the properties of metal materials is summarized, and future research on the magnetic field effect on solid metal has been prospected.

In this study, the microstructure and mechanical properties of laser melting deposited 7050 aluminium alloy are investigated. An anisotropic microstructure is observed in the alloy: the columnar-grained structure on the building plane and a fine equiaxial structure on the scanning plane. Pores are the main metallurgical defects found but a higher energy input can significantly reduce large pores. The mechanical properties can be significantly improved with heat treatment. After being subjected to multiple solution and aging treatments, the hardness, ultimate tensile strength and elongation at break of the printed alloy increase by 58.6%, 14.06% and 27.8%, respectively. This research offers a reference for the formation technique of large and complex 7xxx series aluminium alloy parts by additive manufacturing.

文章扼要地介绍了铝合金家具的国内外发展情况及其优点和应用情况,以及未来的发展趋势;并根据国内外家具的发展情况,对铝合金家具的未来发展方向提出了建议.

The effect of a pulsed magnetic field on the microstructure of a QAl9-4 aluminium bronze alloy was studied in this work. It was found that the dislocation density, grain boundary angle, and microhardness of the alloy significantly changed after the magnetic field treatment with a peak magnetic induction intensity of 3T, pulse duration of about 100 us, pulse interval of 10 s, and pulse time of 360. EBSD was used to test the KAM maps of the alloy microzone. It was found that the alloy’s dislocation density decreased by 10.88% after the pulsed magnetic field treatment; in particular, the dislocation in the deformed grains decreased significantly. The quantity of dislocation pile-up and the degree of distortion around the dislocation were reduced, which decreased the residual compressive stress on the alloy. Dislocation motion caused LAGB rotation, which reduced the misorientation of adjacent points inside the grain. The magnetic field induced the disappearance of deformation twins and weakened the strengthening effect of twins. The microhardness test results show that the alloy’s microhardness decreased by 8.06% after pulsed magnetic field treatment. The possible reasons for the magnetic field effect on dislocation were briefly discussed. The pulsed magnetic field might have caused the transition to the electronic energy state at the site of dislocation pinning, which led to free movement of the vacancy or impurity atom. The dislocation was easier to depin under the action of internal stress in the alloy, changing the dislocation distribution and alloy microstructure.

目的 探究激光焊接参数对非晶合金焊接接头的组织演变、焊缝成形、晶化程度等的影响规律,以及控制接头晶化的有效途径.方法 采用碟片激光器对Zr58Nb2.76Cu15.46Ni12.74Al10.34Y0.5非晶合金进行激光焊接,对比分析不同激光功率下,焊接速度对接头熔宽和晶化组织形成的影响规律,并对接头各区域微观组织特征及硬度分布进行测试分析.结果 非晶合金激光焊接接头成形良好,焊缝区组织整体为非晶,存在少量纳米晶,热影响区则发生明显晶化现象.当功率为1200 W时,逐渐提升焊接速度,接头晶化率由28.9％降到13.76％,熔宽由2.04 mm收窄至1.8 mm.当功率为4500 W时,逐渐提升焊接速度,接头晶化率从9.99％下降为7.47％,焊缝晶化现象消失,熔宽从1.10 mm降到0.98 mm.结论 调节关键焊接参数可实现焊缝区晶化现象的消失,使热影响区晶化程度降低.大激光功率以及高焊接速度更有利于形成熔宽小、晶化程度低的焊接接头.焊缝区硬度与母材基本保持一致,热影响区由于发生晶化,硬度最高.

Aluminum-zinc-magnesium (Al-Zn-Mg) alloy that is fabricated by using traditional plastic processing is not suitable for laser additive manufacturing due to its tendency to crack. To design aluminum alloy with low hot cracking tendency and is suitable for laser additive manufacturing, an aluminum-zinc-magnesium-scandium (Al-Zn-Mg-Sc) system is proposed in this study. A theoretical model is used to predict the hot cracking susceptibility of this system. The optimized alloy composition is Al-6.5Zn-2.2 Mg-0.4Sc and its formability during laser melting deposition (LMD) is then investigated. An anisotropic microstructure is observed in the alloy: columnar grains with a [001]//Z texture in the building plane and equiaxed grains in the scanning plane. Pores are the main metallurgical processing defects, but a few hot cracks can be seen in the laser melted (Al-Zn-Mg-Sc) alloy. The mechanical properties can be significantly improved through heat treatment: the ultimate tensile strength of the alloy is increased from 258.7 MPa to 390.3 MPa, and elongation of the alloy is increased from 13.1% to 29.6% after solution and aging treatments, thus indicating that the alloy has good plasticity.

Non-oriented 6.5 wt% Si steel thin sheets with three different yttrium (Y) contents (0, 0.012, and 0.03 wt%) were prepared by hot rolling, warm rolling, intermediate annealing, cold rolling and final annealing processes. The effects of the Y content on the microstructure, texture, and magnetic properties of cold-rolled 6.5 wt% Si steel sheets were studied by optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and electron backscattered diffraction. The results showed that the sample with 0.012 wt% Y had the lowest volume fraction of inclusions, and Y played a role in purifying steel. The final average grain size of sheets decreased upon increasing the Y content. As the Y content increased, the {100} texture continuously weakened, and the overall intensity of the η (〈100〉//RD) texture increased first and then decreased, while the intensity of the detrimental γ (〈111〉//ND) texture decreased first and then increased. Adding an appropriate amount of Y optimized the recrystallization texture by promoting the occurrence of shear bands, which provided more nucleation sites for η - fiber oriented grains. When the Y content was 0.012 wt%, the magnetic induction B 50 reached the maximum (1.64655 T) due to the enhanced η texture and weakened γ texture. The sample with 0.012 wt% Y showed the lowest core loss at high frequencies (>5 kHz) because of the favorable grain size. The addition of excess Y increased the number of inclusions and increased γ -fiber oriented grain nucleation, which deteriorated the magnetic properties of non-oriented 6.5 wt%Si steel.

通过循环预拉伸应变-高温退火制备Al-Cu-Li合金单晶,同时探讨循环预拉伸应变-高温退火过程中预拉伸应变量、循环应变退火次数、应变退火温度对Al-Cu-Li合金晶粒长大的影响以及晶粒长大的过程与机制.研究结果表明,通过循环预拉伸应变退火可以使得合金晶粒异常长大,并且成功制备出厘米级别的宏观粗大晶粒,其长大机理主要为应变诱导晶界迁移(Strain-Induced Boundary Migration)形核再结晶异常晶粒长大.此外,分别对Al-Cu-Li合金预拉伸应变量、循环应变退火次数以及应变退火温度对晶粒长大影响进行研究,制定出较优的单晶制备工艺,结果表明较优工艺为Al-Cu-Li合金经0.8％预拉伸应变后在540℃下退火48 h,循环次数2～3次.

Carbide precipitates are effective for improving the strength and stability of high-entropy alloys. In this work, novel-designed Fe60Co10Cr10Ni10Mo5V5 medium-entropy alloys (MEAs) containing 1 wt.% carbon were prepared by vacuum arc melting followed by solid solution treatment and aging. The effects of aging on the microstructure and mechanical properties of the MEAs were investigated. The results showed that the microstructure of the solution-treated alloy was comprised of the face-centered cubic (FCC) matrix, coarse M2C/MC carbides, and tiny fine undissolved MC precipitates distributed on the grain boundaries and inside the grains. A high number density of cube-shaped MC precipitates, with an approximate mean size of 24 nm precipitate within the FCC matrix in the case of aging at 800°C for 2 h, contribute to the highest hardness and tensile strength of the sample without sacrificing its elongation. With increasing aging temperature and time, the size of the MC precipitates increased while their volume fraction decreased. The strengthening effect can be attributed to the combination of the precipitation strengthening and solid solution strengthening.

The microstructure and properties of niobium-containing AISI M3:2 high speed steels (HSSs) fabricated by spray forming and traditional casting have been investigated. The results show that fine and uniformly-distributed grains without macrosegregation appeared in the as-deposited HSSs that differ from those of as-cast HSSs. Nb mostly appears in primary MC carbides, whereas it contributes less to the formation of M6C carbides. The high stabilization of Nb-rich MC carbides can pin the grain boundaries during high-temperature austenitizing process, thus conferring a fine grains and raising the content of dissolved alloying elements. Enhanced precipitation strengthening and fine dispersion of NbC carbides throughout the matrix contribute to the high hardness and red hardness of Nb-containing HSS.

为研究实际生产中大口径铜管的扩径拉拔工艺,基于等比例缩小原则,通过理论解析、有限元仿真和实验验证3种途径对BFe10-1-1铜管扩径拉拔的形变规律及扩径力进行研究,探讨了关键工艺参数对扩径过程的影响规律.结果表明:扩径力随扩径系数、管材壁厚和摩擦系数的增大而增大,随模芯半锥角的增大先减小后增大,在模芯半锥角为12°左右时可获得最小扩径力.理论和有限元预测的扩径力与实测值吻合良好,当扩径系数为1.1时,压入扩口时的扩径力理论和有限元预测值与实验值的相对误差分别为4.1％和0.8％,拉伸扩径时的扩径力理论和有限元预测值与实验值的相对误差分别为3.3％和4.4％.

Hollow spherical and hierarchical structures of ammonium tungsten bronze ((NH4)(x)WO3) were prepared via a two-step hydrothermal method. It was found that the (NH4)(x)WO3 hollow spherical structure without adding citric acid, while the (NH4)(x)WO3 hierarchical structure formed when adding citric acid at the second hydrothermal step. Both structures consist of nanorods and nanoparticles with connected frames. The possible formation mechanism of these two (NH4)(x)WO3 structures was proposed and discussed. The current approach is simple, and can also be applied for the synthesis of other tungsten bronze materials with novel structures.

The goal of this work is to reveal the dynamic mechanical properties and constitutive relationship of a novel low alloy ultra-high strength DT506 steel under high strain rates. The quasi-static state and dynamic compression behavior of the material at the strain rates of 10 −3 –10 3 s −1 were examined using an MTS landmark electro-hydraulic servo universal tester and a Split-Hopkinson bar (SHPB). The results show that DT506 steel is a strain-rate-sensitive material that shows an increase in strength with increasing strain rate. Based on the quasi-static and dynamic compression data, the parameters in the Cowper-Symonds (C-S) and the Johnson-Cook (J-C) models are determined. Since the previously developed models are cannot accurately predict the effect of the strain rate. A new theoretical model is obtained through the optimization of the parameters in the standard J-C model. The optimized model greatly improves the prediction accuracy of the true stress-strain dynamic behavior of materials. This new model is helpful for the verification of the underlying mechanism of the dynamic behavior of the material. Test results may provide basic data for future research on dynamic mechanical properties and constitutive relationship of metal alloys.

In order to efficiently produce high-damping Mn–Cu based alloys, different heat treatment processes were designed in this study, and the influence of the cooling process on the damping property of M2052 alloy was systematically investigated. The results show that the step-cooling process significantly influenced the damping performance of M2052 alloy. Compared with M2052 alloy processed using air-cooling with an internal friction (tan δ ) of 0.087 at a strain amplitude λ = 5 × 10 −4 , the damping capacity was improved by more than 49% through the step-cooling treatment. This was mainly because of the increment of manganese content of in the Mn-rich regions, which is caused by the spinodal decomposition on the low temperature side of the miscibility gap. Meanwhile, the step-cooling treatment significantly suppressed the precipitation of α-Mn, which reduced the negative effect of α-Mn on the damping capacity and kept the Mn content in the Mn-rich regions at a high level. The step-cooling treatment, a novel and effective microstructure control process, provides a new method for the efficient preparation of high-damping M2052 alloy.

为了提高产品的性能,本试验对容器钢的化学成分进行了优化,并采用RCR(再结晶控制轧制)+ACC(加速冷却控制)工艺对250mm厚的连铸坯轧制到30mm厚,轧后进行了正火处理.通过对热轧板和正火板进行金相检验和力学性能测试,分析了轧制工艺与钢板组织和性能的关系.试验结果表明,采用RCR+ACC工艺生产的钢板正火后各项性能均满足技术要求.与常规工艺相比,RCR+ACC工艺生产的正火板组织分布更均匀,-40℃横向冲击功达到154 J,实现了组织和性能的良好匹配.