Influences of Ta, Nb, or Mo additions in Zr-based bulk metallic glasses on microstructure and thermal properties

The master-alloy ingots for casting bulk metallic glasses are routinely prepared by arc melting a mixture of pure elements. This paper addresses the difficulty in achieving complete and homogeneous melting of refractory component additions in Zr-based BMGs using the above procedure, and its influences on the microstructure and thermal behavior of alloys.     

型腔模具主要加工方法浅析

介绍并分析了当前型腔模具主要加工方法，提出选择加工方法的依据。     

光固化快速成形中网形支撑生成算法的研究

本文研究了一种新的光固化快速成形工艺支撑形式——网形支撑,并提出实现STL格式实体支撑的自动生成算法,即对实体按支撑角度分区域支撑生成算法。该算法生成支撑速度快,容易制作,在强度等方面更能满足工艺要求,该算法已成功应用于光固化快速成形系统中。     

快速凝固制备Mg-Al-Zn合金薄带

镁合金的力学性能、抗腐蚀性能及室温塑性都较差,至今它的应用仍受到限制。快速凝固通过改善合金的微观结构,是克服上述局限的有效方法之一。采用双辊旋铸技术快淬制备AZ31镁合金薄带。对双辊转速对薄带厚度及其微观硬度的影响进行了分析。微观硬度随双辊转速的提高而提高。然而,由于AZ31镁合金的Al、Zn含量过少,固溶有限,所以由热处理引起的析出相强化有限,这也是由热处理所引起的微观硬度增幅不大的原因。所以,对AZ31镁合金进行强化处理,应该采用快速凝固细化晶粒的方法较为有效。     

基于SLS原型的快速(重力)铸造工艺

结合SLS快速成形和铸造工艺可以实现金属零件的快速铸造.根据原型材料可熔融和烧失的特性,制定了类似于熔模铸造的快速铸造工艺方案.讨论了快速金属铸件的特点,对快速铸造工艺提出了成功率高、成形性好和性能较高的要求.分析了面向金属零件快速铸造的重力铸造工艺并以实例说明,顶注式浇注系统适用于结构简单且高度不大的快速零件,而阶梯式浇注系统适用于中大型和复杂程度较高的铸件.     

高温耐热Al-Zr-Nb-Ni铝合金的显微组织及析出过程

采用快速凝固法制备了Al85Zr4Nb4Ni7合金薄带，对快速凝固合金条带的激冷态和热处理态的微观结构进行了DSC、X射线衍射和TEM分析。结果表明：在激冷态时，合金组织为过饱和的α-Al、AlNiZr和Al3Zr共存；在400℃退火时，由于AlNiZr相的分解而出现了Al3Ni相；480℃退火以后有未知相析出，组织中晶粒进一步长大。同时讨论了Al3Zr和Al3Ni对Al85Zr4Nb4Ni7合金热稳定性的影响。     

Formation of quasicrystals in Zr–Pd–(Cu) melt spun ribbons and mechanically milled powders

Amorphous Zr₇₀Pd₃₀ and Zr₇₀Pd₂₀Cu₁₀ alloys were prepared by mechanical milling and melt spinnng to compare their devitrification behaviors. The devitrification of mechanically milled Zr₇₀Pd₃₀ and Zr₇₀Pd₂₀Cu₁₀ powders occurs via a single-step, first-order transformation to a stable Zr₂Pd tetragonal structure. This is in sharp contrast to the devitrification of the same amorphous alloys prepared by melt spinning, in which a primary meta-stable quasicrystalline phase forms. Since the mechanical milling process does not involve direct liquid phase formation of an amorphous structure, it is inferred that the short-range order in the solid state derived amorphous powder is different from that in the melt spun ribbon. During mechanical milling of an amorphous melt spun ribbon, crystallization of the quasicrystalline phase appears to precede disordering into an amorphous structure having an different short range order. Deformation of an amorphous melt spun ribbon by repetitive rolling at ambient temperature crystallizes the meta-stable quasicrystalline phase.     

Characteristics on micro-biofabrication by patterning with electrostatically injected droplet

Micro biofabrication technologies have been developing aiming to fabricate 3D artificial organs, 3D scaffolds, and complex tissue structures. We are now developing a new inkjet bio-printing method via electrostatic phenomenon. The merits of the new method are of high resolution, and of ability to eject highly viscous liquid and media. In this paper, we attempted to apply the proposed method for precision printing cells and biomaterials. Living cells and scaffolds have successfully been printed and the biochemical characteristics have been investigated. A 3D cell structure which had a cavity to create blood vessels has also successfully fabricated by this method.     

Non-equilibrium solute partitioning in a laser re-melted Al–Li–Cu alloy

Aluminum–lithium alloy AA2199 was rapidly solidified through the application of a laser re-melting process to determine the relationship between laser pulse energy and microsegregation during solidification. It was determined that laser pulse energies of the order of 0.125–0.5 J s resulted in a fine cellular solidification structure. Through comparison of the measured cell spacing with that predicted by the Kurz–Giovanola–Trivedi (KGT) model it was possible to estimate that solidification front velocities (SFV) of between 3 and 25 cm s^?1 occurred during solidification. The SFV calculated from the KGT model was then input into the continuous growth model for solute trapping developed by Aziz to predict the deviation from equilibrium partitioning during solidification for all pulse energy levels employed. The chemical profile of lithium within the re-melted samples was measured using X-ray photoelectron spectroscopy and compared with that expected for equilibrium segregation. Measurement of the lattice parameter via X-ray diffraction revealed that the solute trapping phenomenon resulted in the formation of a super-saturated solid solution, as is evident through a reduction of the lattice parameter from 4.0485 Å for the starting material to 4.0399 Å in the material re-melted with a pulse energy of 0.125 J.     

搪玻璃设备的现场快速修复

介绍了搪玻璃设备现场快速修复的步骤、特点及经济效果。本方法的关键是表面清理和修补材料的选择。