混合增粘熔体发泡法制备泡沫铝及其压缩性能的研究

为了减少泡沫铝熔体发泡法中单质钙的用量及增加泡沫铝的强度,研究了单质钙增粘、碳化硅增粘以及混合增粘3种不同的增粘方式,并试图通过混合增粘来达到这一目的。结果表明,借助单质钙和碳化硅组成的混合增粘剂可以制备出形状规则、孔结构均匀的泡沫铝试样。碳化硅增粘为机械增粘,而单质钙增粘为化合物增粘,混合增粘将两种增粘机制结合起来,实现了共同增加粘度的作用。混合增粘可以在达到熔体发泡所需粘度的同时减少单质钙的用量,还可以在一定程度上提高泡沫铝的强度,达到了碳化硅颗粒增粘和增强的双重目的。     

发泡法制备泡沫铝

介绍了发泡法制备泡沫铝的工艺过程，论述了增粘、混合、发泡和冷却４个过程对泡沫铝孔结构的影响。采用ＴｉＨ２的缓释技术，可大大延缓ＴｉＨ２的反应时间，使ＴｉＨ２均匀混入铝熔体，从而制得孔结构均匀、吸声性能优良的泡沫铝。     

泡沫SiC颗粒增强铝基复合材料的制备工艺和拉伸强度

介绍了一种新的泡沫金属材料－泡沫SiC颗粒增强铝基复合,泡沫的孔隙率为60％－85％。用TiH2作发泡剂,采用直接发泡工艺制备。由于复合材料熔体自身粘度较大,不需要采用任何增粘措施,发泡工艺简单,易于操作,该泡沫材料比普通泡沫铝或铝合金具有更高的抗拉、抗压强度。     

胍基聚电解质与聚丙烯共混体系的流变性能研究(Ⅰ)PHGC/PP

以毛细管流变仪研究了不同组成的 PHGC/ PP共混体系的熔体流变行为 ,分别讨论了熔体粘度与温度、共混体系组成之间的关系 ,并在电镜下观察了共混体系的相态结构 ,分析了共混体系的相容性对熔体流变行为的影响。结果表明 ,在实验条件下 ,PHGC/ PP共混体系为切力变稀型流体 ;PHGC与 PP相容性较差 ,在 PP中分散颗粒较大 ;PHGC含量较低时 ,熔体粘度有极小值 ,随着温度和剪切速率的变化 ,熔体粘度随 PHGC含量的变化呈现出不同的变化趋势。在 PHGC含量为 2 .5 %时 ,非牛顿指数最大 ,粘流活化能最小     

铝熔体泡沫形成过程中粘度对孔结构影响

采用简便有效的测量搅拌电机功率的方法控制铝熔体泡沫化过程的粘度，研究了粘度、温度与孔结构的关系，随熔体表观粘度提高泡沫孔径变小。合适的表观粘度有利于提高泡沫孔径分布的均匀性、获得高的孔隙率、泡沫孔径随温度提高而增大。     

CPE对PVC／PP体系流变性能的影响

利用Instron毛细管流变仪对PVC/PP及PVC/PP/CPE共混体系的流变性能进行了细致的考察。结果发现,增容剂CPE对PVC/PP体系的流变性能起着双重作用。一方面,在PVC/PP共混物为“海-岛”结构时,CPE起着作为橡胶的增粘效应;另一方面,在PVC/PP共混物为“互锁”结构时,CPE的润滑增塑效应使得它起着降低“互锁”共混物熔体粘度、提高成型加工性能的作用。     

防锈闭孔泡沫Al-Mg-Re基合金的制备与性能

在熔体发泡法制备工艺基础上,引入合金化阻燃技术,制备了Al-Mg-Re基防锈闭孔泡沫铝合金.实验结果表明,熔体发泡前同时加入Mg、Ca和稀土制备的防锈闭孔泡沫Al-Mg-Re基合金孔结构均匀,由于Mg和稀土元素的双重作用,Al-Mg-Re基防锈闭孔泡沫铝合金具有优异的耐腐蚀性能.     

工艺因素对Al-Si合金熔体粘度的影响

采用旋转柱体法系统地对纯铝及铝硅合金在液相线以上不同温度的粘度进行了研究。实验结果表明:随着温度的升高,熔体的粘度都呈减小的趋势;且当Si含量增至5%时,熔体的粘度在720～790℃之间存在着异常变化,可能是熔体结构发生了改变;在较大过热度(ΔT=100℃或135℃)时,Si含量在不超过7%条件下,Si含量对Al-Si合金熔体粘度的影响较小;而当Si含量达到9%或11%以上时,Si含量对熔体粘度的影响变大。     

胍基聚电解质与聚丙烯共混体系的流变性能研究(I)PHGC/PP

以毛细管流变仪研究了不同组成的PHGC／PC共混体系的熔体流变行为,分别讨论了熔体粘度与温度、共聚体系组成之间的关系,并在电镜下观察了共混体系的相态结构,分析了共混体系的相容性对熔体流变行为的影响。结果表明,在实验条件下,PHGC／PP共混体系为切力变稀型流体;PHGC与PP相容性较差,在PP中分散颗粒较大;PHGC含量较低时,熔体粘度有极小值,随着温度和剪切速率的变化,熔体粘度随HGC含量的变化呈现出不同的变化趋势。在PHGC含量为2．5％时,非牛顿指数最大,粘流活化能最小。     

碳酸钙制备小孔径中等孔隙率类球形孔泡沫铝及其合金

与传统的Ca增黏与TiH2发泡的泡沫铝熔体发泡制备方法不同,CaCO3在铝熔体中可同时用作增黏剂和发泡剂.现有TiH2泡沫铝制备技术在制备小孔径类球形孔泡沫铝及合金方面存在困难,以轻质Ca-CO3颗粒为基础研制的新型泡沫铝增黏发泡剂,其热分解特性平缓,通过理论与实验确定了CaCO3在制备过程中的使用比例,分析了孔结构并讨论了CaCO3在铝熔体中的分解热力学问题,稳定制备出小孔径(0.4-1.1mm)、中等孔隙率(40-79%)的类球形孔泡沫铝及其合金.     

The relationship between thermal decomposition properties of titanium hydride and the Al alloy melt foaming process

Using a new temperature programmed decomposition (TPD) theory and related experimental technique, a set of thermal decomposition kinetics equations of titanium hydride can be acquired by separating and simulating its TPD spectrum. According to these equations, the relation curve of decomposition quantity and time for titanium hydride at temperature of 940 K is obtained and the result coincides well with the Al alloy melt foaming process, which provides a scientific basis for controlling the Al alloy melt foam and then the Al alloy foams with different pore structure are successfully prepared.     

球形孔泡沫铝合金三明治梁的三点弯曲变形

研究了球形孔泡沫铝合金的单轴压缩性能,得到了抗压强度与相对密度的关系;与多边形孔泡沫铝合金和泡沫纯铝作了对比,发现球形孔使力学性能有了较大的提高.根据球形孔泡沫铝合金三明治梁三点弯曲的载荷(P)位移(δ)曲线研究了四种常见破坏模式并建立了破坏模式图.用极限载荷公式得到的计算值与极限载荷的实验值吻合良好.球形孔泡沫铝合金力学性能高于多边形孔泡沫铝合金及泡沫纯铝,因而其三明治梁的力学性能最好.     

球形孔通孔和闭孔泡沫铝合金的超声衰减性能

研究了球形孔通孔和闭孔泡沫铝合金在1 MHz～10 MHz的超声衰减性能.结果表明:泡沫铝合金的超声衰减性能决定于其孔结构;通孔泡沫铝合金的超声衰减系数α随着孔径d的减小、孔隙率Ps减小和比表面积Sv的增加而增大;闭孔泡沫铝合金的超声衰减系数α随孔径d的减小、孔隙率Ps的增加和比表面积Sv的增加而增大;当孔径d、孔隙率Ps相近时,闭孔泡沫铝合金的超声衰减性能优于通孔泡沫铝合金;在1 MHz～10 MHz二者是具有良好阻尼性能的轻质材料.其衰减机制为在弹性范围内超声应力波在具有大量孔隙界面的泡沫铝合金中的衰减.     

Ti—5Al,5Sn合金冷坩埚感应熔炼过程中Al和Sn元素的挥发研究

利用所建立模型研究了Ｔｉ－５Ａｌ－２,５Ｓｎ合金感应凝壳熔炼（ＩＳＭ）过程中Ａｌ、Ｓｎ元素的挥发控制方式,并在此基础上研究了熔体温度和真空室压和对Ａｌ、Ｓｎ挥发速率的。结果表明,实际熔炼条件下Ａｌ、Ｓｎ的挥发都由界面挥发反应单一控制,真空室压力对挥发速率的影响具有明显的临界值,当压力低于此临界值时,挥发速率几乎没有什么粉经,两当压力高于此值时,挥发速率迅速降低。     

Wettability modification and the subsequent manipulation of protein adsorption on a Ti6Al4V alloy by means of CO<Subscript>2</Subscript> laser surface treatment

Improvements in the wettability of the Ti6Al4V alloy following CO₂ laser treatment were identified as being due mainly to the increase in surface roughness, surface oxygen content and surface energy of the material. Untreated and mechanically roughened samples had higher amounts of adsorbed albumin and lower amounts of adsorbed fibronectin than CO₂ laser treated samples. Moreover, as the wettability of the Ti6Al4V alloy increased the adsorbed amounts of fibronectin increased, while the adsorbed amounts of albumin decreased—indicating the controllability of the CO₂ laser process. From this finding it is possible to assert that the wettability of the Ti6Al4V alloy was the prime influence on the observed changes in in vitro protein adsorption. Further, the noted considerable change in the polar component of surface energy, , on the protein adsorption implied that the protein adsorption on the Ti6Al4V alloy was probably due to the polar and chemical interactions. This work has demonstrated that CO₂ laser radiation could be a suitable means to modify the wettability of the Ti6Al4V alloy and thereby manipulate protein adsorption and consequently render the material more bone cell responsive.     

高比强高孔隙率泡沫铝合金三明治梁

研究了高比强泡沫铝合金和泡沫纯铝的单向压缩和剪切性能,对以高比强泡沫铝合金为夹芯的三明治梁失效模式的尺寸范围和承载能力进行了理论计算,结果与实验结果符合得很好.给出了泡沫铝合金三明治梁的设计方法,表明在较小的设计载荷下,三明治梁是以刚度作为设计的控制条件;在较大的设计载荷下,以相对强度为设计的控制条件.泡沫铝合金三明治梁与泡沫纯铝三明治梁的对比表明,在刚度设计控制条件下,前者的刚度是后者的1.00～1.185倍.在强度设计控制条件下,剪切破坏和压凹破坏失效模式下的泡沫铝合金三明治梁比泡沫纯铝三明治梁的极限强度分别提高57%～180%和90%～220%.     

Parametric optimization of surface roughness castings produced by Evaporative Pattern Casting process

In the present paper Taguchi's approach has been applied to the Evaporative Pattern Casting (EPC) process of Al–7%Si alloy to determine the most influential control factors which will provide better and consistent surface roughness to the castings regardless of the noise factors present. In order to evaluate the effect of process parameters such as grain fineness number, time of vibration, degree of vacuum and pouring temperature on surface roughness of EPC process castings, the Taguchi parameter design and optimization approach is used. Through the Taguchi's parameter design approach, optimal levels of process parameters have been determined. The results indicated that the grain fineness number, time of vibration, degree of vacuum were the significant parameters in deciding the surface roughness of Al–7%Si alloy castings. Pouring temperature was the insignificant parameter. The predicted optimal value of surface roughness of Al–7%Si alloy castings produced by EPC process was 2.31 μm. The results were confirmed by further experiments.     

A novel approach to produce Al-alloy foams

The stability of Al foams during processing is crucial to producing uniform Al foams. Once pores form during processing, no matter which conventional methods are used, the pores grow and/or merge into large ones, which could cause Al foams to “collapse”. Therefore, it has attracted great attention of researchers to enhance the stability of Al foams during processing for improved quality of Al foams. A novel approach to produce Al-alloy foams, “Rheofoaming”, is presented in this paper. A twin-screw rheomixer fitted with a gas inlet near the end cap is used in this work. The mechanism of this approach is firstly to increase the viscosity of semisolid slurry of Al alloy by adding sub-micron Al₂O₃ particles and then to mix N₂ gas with the semisolid slurry using a twin-screw rheomixer, which can offer high shear rate and intensive turbulence. The gas pores in the semisolid slurry are stretched and broken into smaller ones in the rheomixer. Al foams are very stable during the processing due to small pore sizes and high viscosity of semisolid slurry. The microstructure of rheofoamed Al foams and the process of this new approach have been described in this paper.     

Synthesis of SiC/Al Co-Continuous Composite by Spontaneous Melt Infiltration

1. IntroductionBecause of the adVantages such as ease of fabrication, low cost and near net shape forming capability,liquid metal infiltration has become a popular technique to fabricate metal matriX composites(MMCs)with high contellt reinforcements. In the process ofmelt infiltration, liquid metal penetrates into the continuous porosity of a packed ceramic filler or preform either by aPPlied positive or negative pressuresuch as in vacuum infiltration[1], pressurized liquldmetal infiltration…