NiAl-Cr(Mo)-Hf共晶合金定向凝固组织的特性及力学性能

采用高温度梯度定向凝固装置制备NiAl-Cr(Mo)-Hf共晶合金,系统地研究了凝固速率对合金凝固组织和力学性能的影响.随凝固速率的增大,固液界面依次呈现平、胞、枝的形貌,而且共晶胞的尺寸和层片间距随之减小.同时发现当凝固速率在3.33μm/s到16.7μm/s范围内变化时,合金的力学性能随凝固速率的增大而增大.(Mo)-Hf;定向凝固;显微组织;力学性能     

快速凝固Al—Ti—B和Cu—P对Al一13.5Si—xCu—yNi合金组织和性能的影响

在ZL108中加入Cu—Ni（Ni含量为40％）中间合金,制成Al-13．5Si—xCu—yNi合金,研究此种合金较ZL108合金在力学性能上的优越性,并采用经快速凝固处理的Al—Ti—B和Cu-P薄带对其进行细化变质处理,观察经细化变质处理后的合金的显微组织并测试其力学性能,确定其最佳变质方案,与经普通块状变质剂变质后的合金进行比较,结果表明经快淬薄带状变质剂变质后的合金组织更加细化,综合力学性能也有较大的提高。     

快速凝固AB_5型贮氢合金显微组织、吸氢及电化学性能

对AB5型快速凝固贮氢合金与其铸态合金在显微组织、吸氢性能、电化学性能等方面进行了对比研究。发现快速凝固合金有细小的 1～ 5 μm胞状、等轴状微晶组织 ;快速凝固合金的P C T曲线平台比铸态合金平缓 ,且压力低 ;快速凝固合金容量及活化性能低于铸态合金 ,但经退火后可以部分改善 ;快速凝固合金电极循环寿命明显优于铸态合金 ,主要是因为合金的晶粒细小可以抑制合金的微粉化和氧化。     

合金结构钢25CrMnSiA生产及性能研究

本文结合生产实际情况，对影响25CrMnSiA钢板性能的工艺因素进行分析及实验，最终选择出合理的工艺制度，获得了较为满意的结果。     

Evolution of Microstructure During Solidification of an Aluminium Alloy Under Stirring

In the present work, the evolution of microstructure during solidification of A356 alloy under stirring is performed experimentally in a high temperature concentric viscometer. The stirring during solidification results a semisolid slurry in the annular space between the cylinders. This slurry is removed periodically during processing using a vacuum removal quartz tube and quenched in water for micrograph analysis. From the micrograph analysis, the shape, stacking arrangement and corresponding microstructural evolution of the suspended primary particles in the slurry are studied. The work also predicts the fraction of solid present in the extracted slurry. Finally, the effect of microstructure and the solid-fraction on the slurry viscosity is presented.     

快速凝固Al-Cu-Mg-Fe-Ni合金的显微组织和析出过程

利用X射线衍射、DSC、透射电镜和能谱分析研究了快速凝固Al 4Cu Mg 3Fe 4Ni (质量分数 )合金急冷态和退火态的显微组织 ,同时测定了该合金的显微硬度。结果表明 :快凝合金急冷态组织为过饱和α Al基固溶体和Al3 Ni相 ;当快凝合金经 4 0 0℃× 1h处理后 ,有少量S相 (CuMgAl2 )析出 ;快凝合金经 4 0 0℃× 9h处理后 ,出现了FeNiAl9弥散相 ;在合金组织中未见Al Cu Fe和Al Cu Ni相。随时效时间的增加 ,快凝合金的显微硬度不断增加 ,达到峰值后硬度缓慢下降 ,之后随FeNiAl9析出硬度又重新增加。     

Columnar-to-Equiaxed Transition and Equiaxed Grain Alignment in Directionally Solidified Ni3Al Alloy Under an Axial Magnetic Field

The effect of an axial magnetic field on the solidification structure in directionally solidified Ni-21.5Al-0.4Zr-0.1B (at. pct) alloy was investigated. The experimental results indicated that the application of a high magnetic field caused the deformation of dendrites and the occurrence of columnar-to-equiaxed transition (CET). The magnetic field tended to orient the 〈001〉 crystal direction of the equiaxed grains along the magnetic field direction. The bulk solidification experiment under a high magnetic field showed that the crystal exhibited magnetic crystalline anisotropy. Further, the thermoelectric (TE) magnetic force and TE magnetic convention were analyzed by three-dimensional (3-D) numerical simulations. The results showed that the maximum value of TE magnetic force localized in the vicinity of the secondary dendrite arm root, which should be responsible for the dendrite break and CET. Based on the high-temperature creep mechanism, a simple model was proposed to describe the magnetic field intensity needed for CET: \( B \ge kG^{ - 1.5} R^{1.25} \). The model is in good agreement with the experiment results. The experimental results should be attributed to the combined action of TE magnetic effects and the magnetic moment.

     

1420铝锂合金铸锭加热过程中的组织变化

研究了1420铝锂合金铸锭在加热过程中组织和强度的变化规律。随着铸锭加热保温时间的延长,合金中的析出相逐步溶入基体中．晶界平衡相尺寸变小．晶界连续性程度增加。晶界无沉淀带(PFZ)窄化．直至完全消失;合金晶界强度逐渐提高．最后甚至超过晶内强度。     

Microstructure Formation and Mechanical Properties of AZ31 Magnesium Alloy Solidified with a Novel Mechanical Vibration Technique

A novel mechanical vibration for refining microstructure is reported where vibration energy was directly exerted into a molten alloy by a vibrating horn, and the vibrating horn was melted during vibration. Effects of vibration intensity and melt superheat on the microstructure and mechanical properties of AZ31 magnesium alloy were investigated. It is confirmed that the melting of the vibrating horn could effectively extract the superheat and latent heat from the interior of the molten alloy, leading to rapid cooling during the initial stage of solidification, and the cooling rate is strongly dependent on the vibration acceleration and melt superheat. This study showed that it was difficult to refine the solidified microstructure when the treated alloy was kept in the full liquid state within the entire vibrating duration. A significantly refined microstructure was obtained by applying mechanical vibration during the nucleation stage, and a globular microstructure could form in a few seconds after solidification. When the molten alloy was treated from 920 K to 903 K (647 °C to 630 °C), with increasing vibration acceleration from 2.5 to 19 m s^?2, the coarse dendritic microstructure of the produced AZ31 billets transformed into a well-refined, reasonably uniform, and non-dendritic one, and mechanical properties were improved significantly. Moreover, the mechanisms of microstructure formation are discussed.     

Structure Modification of Alloy Solidified With Electromagnetic Field

A S45C carbon steel has been solidified under different electromagnetic conditions to investigate the effect of the electromagnetic force imposition and its imposing period on the solidified structure in this study.For excitation of the electromagnetic force,a static magnetic field and a direct electric current were simultaneously imposed on a sample under a certain period of the solidification.After the solidification,the microstructures were observed and compared each other.As the results,microstructure of the S45C steel under the simultaneous imposition of a static magnetic field of 1T and a direct electric current of 20A in the latter stage of its solidification was dendritic while it was globular if the electromagnetic force was imposed during the whole solidification period.     

双向定向凝固超磁致伸缩材料的磁性能研究

采用电弧熔炼-定向凝固法,得到了具有穿晶形态的双向(径向和轴向)定向多晶稀土超磁致伸缩材料。对试样横截面和纵截面X射线衍射实验证实,我们制备的GMM棒在轴向和径向同时具有良好的择优取向。测试了材料的压应力效应,当压应力为29.7MPa时,材料的饱和磁致伸缩达到1481×10-6,与0MPa时相比增加了510×10-6。测量了材料的逆磁致伸缩效应;用自行设计的方法测量了材料的损耗。对上述效应进行了分析讨论。     

A1-Si-Cu合金低温力学性能的研究

主要以Al-Si-Cu合金为研究对象,研究了低温变化对锶变质后的Al-Si-Cu合金组织及性能的影响。变质处理后的Al-si-Cu合金的抗拉强度和屈服强度随温度的降低均升高,同时伸长率和断面收缩率随温度的降低也略有上升。通过对Al-si-Cu合金金相观察,加入Sr元素后,合金的组织得到显著细化。变质后的Al-si-Cu合金在低温下具有更好的力学性能。     

C5240 铜合金加工过程的组织演变与力学性能

通过摸索配料和铸造工艺,制备高强高弹 C5240 铸坯,并进一步通过金相组织观察和能谱分析研究电磁搅拌对 C5240 合金及 Sn 元素分布的影响规律。结果发现,施加电磁搅拌对 C5240 铸坯沿着厚度方向 Sn含量分布均匀化改善有着明显的影响 ;此外,中间退火对屈服强度和抗拉强度影响不大,但有效改善断裂延伸率,且有助于后续加工 ;在薄带轧制过程中,电导率没有随轧制道次增加而降低,这说明位错对电导率的降低作用没有固溶原子大。     

急冷Al-Mn合金中准晶相的形态和化学组成

使用透射式电子显微镜(TEM)观察了Al-12Mn和Al-10Mn-2Fe合金中准晶相的显微形态,选区电子衍射(SAD)做结构分析,用TEM的能谱附件(EDXS)分析准晶相的化学成分。结果表明,典型的准晶相具有菊花状形态,其当量组成非常接近Al₄Mn,准晶相的形态表明它的形成长大机制可能介于非晶和晶体之间;而且,铁的加入促进了合金中准晶相的形成。     

快速凝固AB5型贮氢合金显微组织、吸氢及电化学性能

从AB5型快速凝固贮氢合金与其铸态合金在显微组织、吸氢性能、电化学性能等方面进行了对比研究。发现快速凝固合金有细小的1－5μm胞状、等轴状微晶组织、快速凝固合金的P－C－T曲线平台比铸态合金平缓,且压力氏;快速凝固合金容量及活化性能低于铸态合金,但经退火后可以部分改善;快速凝固合金电极循环寿命明显优于铸态合金,主要是因为合 晶粒细小可以抑制合金的微粉化和氧化。     

Hot-Tearing Susceptibility of Ternary Mg-Al-Sr Alloy Castings

The susceptibility of Mg-Al-Sr alloys to hot tearing during permanent mold casting was investigated using constrained rod casting (CRC) in a steel mold. The alloys included Mg-xAl-1.5Sr and Mg-xAl-3Sr, where x = 4, 6, or 8 wt pct. The hot-tearing susceptibility (HTS) was determined based on the widths and locations of the cracks in the rods. With the Mg-xAl-1.5 Sr alloys, the HTS decreased significantly with increasing Al content. With the Mg-xAl-3Sr alloys, the trend was similar but not as significant. At the same Al content, the HTS was significantly lower at 3 wt pct Sr than at 1.5 wt pct Sr. To help understand the HTS of these alloys, the solidification path and phase fractions were calculated for each alloy. The HTS was found to increase with increasing fraction solid at the end of primary solidification.