Gasar工艺获得均匀藕状多孔结构的气压选择

在用金属-气体共晶定向凝固（Gasar）制备藕状规则多孔金属的工艺中,气体压力是对多孔结构影响最大且最方便调控的工艺参数,在讨论Gasar工艺中所用气体种类选择原则的基础上,通过分析Gasar凝固过程,给出了获得指定气孔率且气孔尺寸分布和位置分布都均匀一致的理想藕状多孔结构的气压选择条件．以Mg-H系为例从实验上验证了该选择条件,为制备高质量的藕状多孔金属提供了合理的工艺参数．     

金属-气体共晶定向凝固制备藕状多孔金属的研究

金属-气体共晶定向凝固(Gasar)是一种制备规则多孔金属的新工艺.利用自行开发的Gasar装置,成功制备了具有规则气孔分布的藕状多孔金属Mg,并研究了铸型预热温度和气体压力等工艺参数对气孔率、气孔大小和分布的影响.结果表明:提高铸型预热温度可以完全消除无气孔金属壳;随着氢气压力的增大,铸锭的平均直径都在减小;在整个Gasar凝固中约有8%左右的氢气溢出.     

藕状多孔金属Mg的Gasar工艺制备

金属／气体共晶定向凝固(Gasar)是一种制备规则多孔金属的新工艺．本文利用自行开发的Gasar装置，成功制备了具有规则气孔分布的藕状多孔金属Mg，并研究了气体压力对气泡形核、气孔率、气孔大小和分布的影响。     

藕状规则多孔结构形成的压力条件和气孔尺寸的演变规律

金属-气体共晶定向凝固（Gasar）是一种制备规则多孔金属的新工艺,本工作通过分析气泡的生长条件,建立了藕状多孔结构形成的压力判据（H2气和Ar气分压比）,并从实验上研究了凝固压力对气孔尺寸的影响规律,结果表明,随着凝固压力（气体总压）的增大,气孔平均直径不断降低。     

Gasar工艺下藕状多孔银的气孔结构研究

金属-气体共晶定向凝固（Gasar)是制备藕状多孔金属的新工艺,利用自行研制的Gasar装置,成功地制备了不同纯氧分压下的藕状多孔银试样,研究了氧气分压对藕状多孔银气孔形貌（气孔率、气孔尺寸和分布、气泡形核）的影响。结果表明：氧气分压对气孔形貌影响十分显著。随着氧气压力的增加,气孔率增大而平均气孔直径减小。     

Ag-O系定向凝固制备藕状多孔Ag

金属-气体共晶定向凝固(Gasar)是一种制备藕状多孔金属的新工艺,在高压纯氧气氛中,利用自行研制的Gasar模铸装置制备了藕状多孔Ag试样,并研究了氧气压力对气孔率、平均气孔直径的影响。结果表明:在多孔Ag中,氧气压力对气孔率和平均气孔直径的影响十分显著。随着氧气压力的增加,气孔率增大,而平均气孔直径减少,当氧气压力为0.5 MPa时,气孔分布最为均匀。     

纯氧分压Gasar工艺下藕状多孔银的气孔结构研究（英文）

金属-气体共晶定向凝固(Gasar)是制备藕状多孔金属的新工艺,利用自行研制的Gasar装置,制备了不同纯氧分压下的藕状多孔银试样,研究了氧气分压对藕状多孔银气孔形貌(气孔率、气孔尺寸和分布、气泡形核)的影响。结果表明:氧气分压对气孔形貌影响十分显著。随着氧气压力的增加,气孔率增大而平均气孔直径减小。     

气压对藕状多孔Cu-Cr合金气孔结构及形貌的影响

采用金属/气体共晶定向凝固工艺(Gasar),在不同氢气压力条件下制备了藕状多孔Cu-Cr合金,研究了氢气压力对藕状多孔Cu-Cr合金气孔结构和形貌因子的影响。结果表明,当氢气压力大于气孔形成临界压力时,随氢气压力的增大,气孔率和孔隙密度增大,而平均气孔直径缓慢减小;当氢气压力大于气体逸出临界压力时,气孔率和平均气孔直径急剧减小,而孔隙密度大幅增加;此外,随氢气压力的增加,气孔形貌因子逐渐减小。     

Al-H系定向凝固制备多孔Al

传统多孔金属材料大多以Al为基,其气孔多为随机分布的不规则形状.而作为规则多孔金属的制备方法--金属/气体共晶定向凝固法(又称Gasar工艺)业已成功应用于Mg,Cu,Ni,Ag,Fe和Si等多种材料,但这一工艺对于Al却并不适用本工作对此进行的实验研究和理论分析认为,Al熔体中氢气溶解总量过少,加之目前Gasar工艺下Al-H体系的凝固速率较低,因此不能维持固、气两相协同共生生长,导致无法直接采用Gasar工艺制得藕状规则多孔Al.     

用金属/气体共晶二维定向凝固法制备放射状规则多孔Mg

采用热传导方向为径向的金属一气体共晶二维定向凝固方法（二维Gasar）,在纯氢和氢、氩混合气氛下制备了气孔沿径向规则分布的放射状多孔金属Mg．研究了放射状多孔金属结构的特点以及气体压力等工艺参数对孔隙率、孔径和气孔分布的影响．结果表明,在圆柱形试样的二维定向凝固过程中,金属一气体共晶形成的体积膨胀会在凝固前沿的液相中产生大的对流,影响气孔的生长方向和规则程度,同时还会导致气体的逸出．随混合气体中氩气分压的增大,逸出程度下降;当氩气分压大于氢气分压时,气体的逸出被完全抑止．由此可以准确地预测出放射状规则多孔金属的孔隙率．     

固/气共晶定向凝固中的工艺判据

气体压力和熔体过热度决定熔体中气体溶解量从而直接影响多孔试样的气孔率.通过理论分析建立了固/气共晶定向凝固中气体逸出和藕状多孔结构形成所需的过热度和气体压力判据.以金属/氢共晶为例,计算结果表明,过热度和氩气分压均应有一适中的范围:给定氢气和氩气分压时,过热度应高于藕孔形成临界过热度而低于氢气逸出临界过热度;给定过热度和氢气分压时,氩气分压应高于氢气逸出临界氩气分压而低于藕孔形成临界氩气分压.该分析结果从藕状多孔Mg的实验结果得到了验证,可以作为高质量规则多孔材料实际制备过程的工艺参数指导原则.     

Effect of transference velocity and hydrogen pressure on porosity and pore morphology of lotus-type porous copper fabricated by a continuous casting technique

A continuous casting technique was developed to fabricate, in a pressurized hydrogen atmosphere, lotus-type porous copper with long cylindrical pores aligned parallel to the solidification direction. The molten copper dissolving the hydrogen was pulled downward to be solidified through a cooled mould at a given transference velocity. This technique has the benefit of producing long-sized lotus-type porous metal slabs as long as 700 mm. The effects of the hydrogen gas pressure and the transference velocity on the porosity and the pore morphology were investigated. The porosity was independent of the transference velocity but dependent on the hydrogen gas pressure. The average pore diameter and pore length were affected by the changes of both the transference velocity and hydrogen gas pressure. The change of transference velocity affected the pore formation position near the slab surface. The porosity and pore size were therefore well controlled by the transference velocity and hydrogen gas pressure. It is concluded that the continuous casting technique is a promising method for the mass production of lotus-type porous metals.     

Fabrication of lotus-type porous micro-channel copper by single-mold Gasar technique

A single-mold Gasar technique was developed to produce lotus-type porous micro-channel copper with uniform porous structure. In this paper the effect of withdrawal rate on the solid/liquid interface morphology and the corresponding porous structure was systematically investigated, especially the pore morphology, pore growth direction, porosity, and pore diameter of porous copper ingots. In addition, a temperature field simulation was carried out based on ProCast software to investigate the shape and movement velocity of the solidifying solid/liquid interface. The experimental results show that the solidification interface changes from convex to planar, then to concave shape with an increase in withdrawal rate. The average porosities of copper ingots are constant and independent of the withdrawal rate. The average pore diameter decreases with an increase in withdrawal rate.     

Fabrication of lotus-type porous Mg−Mn alloys by metal/gas eutectic unidirectional solidification

Lotus-type porous Mg–xMn (x=0, 1, 2 and 3 wt.%) alloys were fabricated by metal/gas eutectic unidirectional solidification (the Gasar process). The effects of Mn addition and the fabrication process on the porosity, pore diameter and microstructure of the porous Mg−Mn alloy were investigated. Mn addition improved the Mn precipitates and increased the porosity and pore diameter. With increasing hydrogen pressure from 0.1 to 0.6 MPa, the overall porosity of the Mg−2wt.%Mn ingot decreased from 55.3% to 38.4%, and the average pore diameter also decreased from 2465 to 312 μm. Based on a theoretical model of the change in the porosity with the hydrogen pressure, the calculated results were in good agreement with the experimental results. It is shown that this technique is a promising method to fabricate Gasar Mg–Mn alloys with uniform and controllable pore structure.