凝固模式对定向凝固多孔铜锰合金气孔结构的影响

采用金属-气体共晶定向凝固工艺（GASAR工艺）,制备气孔定向排列的多孔铜锰合金,并研究气孔结构的变化。结果表明：这种变化主要取决于合金的凝固模式（平面凝固、柱状胞晶凝固、柱状枝晶凝固、等轴枝晶凝固）,而合金凝固模式由合金的凝固过程决定。通过数值模拟发现,随着合金凝固的进行,合金的凝固模式从胞晶凝固向柱状枝晶凝固过渡,最终变为等轴枝晶凝固。通过升高合金熔体温度和铸型的预热温度,可以缩小等轴枝晶凝固的范围,扩大定向生长气孔的区域。     

气压对定向凝固藕状多孔镁的气孔分布影响

采用统计分析方法,通过孔径分布、气孔最邻近距离和局部气孔率定量分析定向凝固藕状多孔镁横截面上的气孔分布特征,并在此基础上分析气压对藕状多孔镁气孔分布的作用规律。结果表明:纯氢条件下气压越高,孔尺寸分布越趋于一致、孔位置和气孔结构单元分布越均匀;氢气分压一定,选择合适的氩气分压可使熔体共晶凝固时,孔尺寸、孔位置和气孔结构单元的分布最均匀。     

气体压力对定向凝固多孔Cu气孔结构的影响

利用自行开发研制的Gasar装置,在H2和Ar的高压气氛中制备了具有规则气孔结构的定向凝固多孔Cu,并研究气体压力对多孔Cu气孔结构的影响.结果表明:当H2压力一定时,随着Ar压力增加,气孔率逐渐减小;当Ar压力一定时,随着H2压力的增加,气孔率呈现先增加后减小的趋势;随着H2压力的增加,气孔的平均直径减小,尺寸分布均匀性提高.     

凝固模式对Gasar多孔Cu-Cr合金结构及组织影响

在0.6 MPa纯H2气氛中,采用金属/H2共晶定向凝固(Gasar)技术制备得到Gasar多孔Cu-x Cr合金。研究了Cr含量、凝固模式以及凝固速率对Gasar多孔合金气孔结构和显微组织的影响。结果表明,当合金以平面、胞状及柱状枝晶凝固时,Gasar多孔Cu-x Cr合金能获得定向生长气孔。当凝固方式转变为等轴枝晶凝固时,定向生长气孔发生中断。Gasar多孔Cu-x Cr合金(x=0.8%、1.3%)气孔在共晶相前沿析出,与共晶组织协同定向生长。随Cr含量增加,共晶组织体积百分比增加,孔隙率和孔圆整度进一步增加;随多孔Cu-1.3 Cr合金试样凝固高度增加,凝固速率下降,界面生长方式转变为等轴晶生长方式,则无法得到定向生长气孔。     

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.     

定向凝固多孔Mg-Zn合金的制备及气孔结构（英文）

采用Bridgman型定向凝固法制备出藕状多孔Mg-Zn合金。研究了不同锌含量和氢气压力对气孔形貌的影响。通过理论计算对Mg-1Zn(质量分数,%,下同)合金的孔隙率进行了预测。结果表明,锌元素的加入会对孔结构产生重大影响。随着Zn含量从0%增加到2%,平均孔径增加。随着氢气压力从0.1 MPa增加到0.6 MPa,Mg-1Zn合金的孔隙率明显降低。基于氢气在多组分熔融金属中溶解度的计算模型,Mg-1Zn合金铸锭凝固高度为20 mm的不同氢压孔隙率的计算结果与实验的结果比较吻合。通过组织观察表明,随着Zn含量的增加,凝固组织由柱状晶转变为等轴晶。此外,研究了在不同凝固阶段孔的形成过程,可为在生物医用材料中应用的定向凝固多孔Mg-Zn合金的制备提供理论依据。     

金属/氢共晶定向凝固制备GASAR多孔Cu-Cr合金

在0.6 MPa的纯氢气氛中,采用金属/氢共晶定向凝固技术,制备得到不同Cr含量的GASAR多孔Cu-xCr合金试样(x=0,0.3%,0.5%,0.8%,1.0%,1.3%(质量分数,%)),并研究了Cr含量对多孔Cu-xCr合金气孔率和气孔平均直径的影响规律。结果表明:随Cr含量的逐渐增大,氢在合金熔体中的溶解度相应增加,导致多孔Cu-xCr合金试样的气孔率缓慢增高;此外,随Cr含量的增加,受糊状区宽度变化的影响,气孔的平均直径呈先增大后减小的趋势。     

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。     

定向凝固多孔金属制造人工骨的前景展望

概述多孔材料人工骨发展历史,介绍了定向凝固多孔金属的制备原理、方法与最新进展,并从生物医学结构和性能特点的角度展示了定向凝固多孔金属制造人工骨的前景。     

Zn-2%Cu包晶合金定向凝固的微观组织

对 Ｚｎ－２％Ｃｕ包晶合金进行了定向凝固实验研究，考察了在不同凝固速度条件下获得的凝固组织，并对其组织构成及尺度分布进行了分析 结果表明，组织从低速到高速经历了棒状胞晶—等轴晶—列状胞晶—板状胞晶—共生结构的转变，其中高速组织特征间距λ与凝固速度ｕ之间存在λ·ｖ０．５４７７＝５５０．５的关系，与低速胞晶组织相比较有显著差异；同时在没有出现平界面生长的条件下获得了包晶共生生长组织，由此对包晶共生生长的平界面假设提出了质疑。     

Pore structure and mechanical properties of directionally solidi ed porous aluminum alloys

Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidif ication. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidif ication front are usually formed. In the research, the effects of processing parameters(saturation pressure, solidif ication pressure, temperature, and holding time) on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the f inal pore structure and the solidif ication pressure, as well as the inf luences of Mg quantity on the pore size, porosity and mechanical properties of AlMg alloy were investigated. The results show that a higher pressure of solidif ication tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.     

定向凝固过共晶Nb-Si基合金的组织优化

采用液态金属冷却定向凝固炉制备Nb-16Si-24Ti-10Cr-2A1．2Hf合金,凝固速率分别为1．2、6、18、36、50mm／min,随后对定向凝固速率为50mm／min的合金进行（1400℃,10h）,（1450℃,10h）和（1500℃,10h）的热处理。研究了定向凝固速率和热处理温度对合金微观组织的影响。结果表明：合金的定向凝固组织主要由沿着试棒轴向生长的初生Nb5Si3相和耦合生长的Nbss／Nb5Si3共晶胞组成,在共晶胞边缘,有少量的Cr2Nb存在。横截面上共晶胞边界明显,随着凝固速率的增加,定向凝固组织明显细化,Nbss／Nb;Si,共晶胞形貌也发生变化。合金经过热处理,Nbss连成基体,部分CrENb相熔解,微观成分偏析减小。经过（1450℃,10h1热处理,实现了对过共晶Nb—Si基合金的组织优化。     

Microstructure of directionally solidified Cu-Cr composites

Cu-Cr composites were prepared by self-made directional solidification equipment with the high temperature gradient and double-zone heating. The microstructural evolution was investigated during the directional solidification with the different solidification rate for Cu-1.0%Cr, Cu-1.7%Cr and Cu-5.6%Cr alloys, respectively. It is shown that for the hypoeutectic Cu-1.0%Cr alloy, the general microstructures consist of primary α(Cu) phase and the rod-like or needle-like (α β) eutectics, and for the hypereutectic Cu-1. 7%Cr and Cu-5.6%Cr alloys, α(Cu)phase, primary β(Cr) phase and (α β) eutectics coexist. With the increase of the solidification rate, the morphology evolution of every phase is that, 1st cellular(dendrite) of α(Cu) phase thins and cellular(dendrite) spacing shortens gradually, (α β) eutectics set in α(Cu) cellular or dendrite, and primary β(Cr) phase distributes unevenly on α (Cu) matrix, whose morphology undergoes the change from dendrite to particle.     

Microstructural evolution and corrosion behavior of directionally solidified FeCoNiCrAl high entropy alloy

The FeCoNiCrAl alloys have many potential applications in the fields of structural materials, but few attempts were made to characterize the directional solidification of high entropy alloys. In the present research, the microstructure and corrosion behavior of FeCoNiCrAl high entropy alloy have been investigated under directional solidification. The results show that with increasing solidification rate, the interface morphology of the alloy evolves from planar to cellular and dendritic. The electrochemical experiment results demonstrate that the corrosion products of both non-directionally and directionally solidified FeCoNiCrAl alloys appear as rectangular blocks in phases which Cr and Fe are enriched, while Al and Ni are depleted, suggesting that Al and Ni are dissolved into the NaCl solution. Comparison of the potentiodynamic polarization behaviors between the two differently solidified FeCoNiCrAl high entropy alloys in a 3.5%NaCl solution shows that the corrosion resistance of directionally solidified FeCoNiCrAl alloy is superior to that of the non-directionally solidified FeCoNiCrAl alloy.     

热型连铸锌铝合金定向凝固线材的组织分析

对热型连铸锌铝合金定向凝固线材的铸态及热处理组织进行了观察、分析和讨论。结果表明：热型连铸锌铝合金线材的显微组织为定向生长的平行柱状枝晶组织;共晶合金ZA5的枝状芥是的每个枝晶都由多层片状共晶β和η两相构成,过共晶合金的组织为初生树枝晶和枝晶间共晶组织,其中ZA8,ZA12初生相为β相,ZA22和ZA27的初生相是α相。     

行波磁场对定向凝固Sn-Cd合金界面形貌的影响

对直径为4 mm的Sn?0.65%Cd合金在行波磁场中进行定向凝固,结果发现其界面形貌是丰富多样的。在向上的行波磁场上,随着磁场强度的增大(B≤10.3 mT),平界面和胞状界面交替转变。当加载向下的弱强度的行波磁场(B=3.2 mT)时,界面形貌由浅胞状向深胞状转变。当磁场强度进一步增大时,界面两侧呈现微弱的不一致,但是在强的磁场下界面形貌大致趋向于平界面(B≤10.3 mT)。这种界面的不稳定性可能归因于行波磁场驱动的流动。另外,在向上的行波磁场中界面形状几乎是水平的,但是在向下的行波磁场中界面形状是倾斜的。     

定向凝固Sn-36%Ni包晶合金凝固组织特征长度的表征

通过对Sn?36%Ni包晶合金在恒定温度梯度(G=20 K/mm)下进行的一定速度范围内(v=2~200μm/s)的定向凝固实验，研究凝固组织特征尺度随生长速度v的变化；测量包括一次与高次枝晶间距及枝晶尖端半径在内的凝固组织特征尺度。通过实验结果与理论模型的对比，发现凝固组织特征尺度随生长速度的变化关系为：对于一次枝晶间距有λ1=335.882v?0.21,且与 Kurz?Fisher 模型吻合；对于二次枝晶间距有λ2=44.957v?0.277,且与 Bouchard?Kirkaldy模型吻合；对于三次枝晶间距有λ3=40.512v?0.274；对于枝晶尖端半径有R=22.7v?0.36。实验结果表明，λ1/λ2随着生长速度的增加而增加，λ1/λ3的变化明显较λ1/λ2的小，表明三次枝晶具有与一次枝晶类似的生长特征；而λ1/R的比值随着生长速度的增加而由2增加到2.3，变化很小。     

Phase and its morphologies of Ti-45 % Al alloy directionally solidified at different growth rates

The microstructures of Ti-45%Al(molar fraction) alloy directionally solidified at different growth rates in alumina tube by electromagnetic heating zone melting were studied. The measured temperature gradient of the system is about 104K/m. The microstructures show that the primary solidified phase is β phase at different growth rates. The growth at low rates from 1.94 × 10-6 m/s to 4. 16 × 10-6 m/s results in a transient solid/liquid interface structure from planar to shallow cellular. This transient rate is larger than the theoretical value of vc = 6.94 × 10-7 m/s.Compared with vt = vc/k = 1.01 × 10-6 m/s, the cellular-dendritic transient rate of experiment is observed in the range of 1.67 × 10-5- 2.50 × 10-5 m/s. The primary arm spacing decreases with increasing growth rate.