AlTiC中间合金组织遗传性的研究

详细论述了采用不同铸造工艺制取的相同成分不同组织形貌的AlTiC中间合金。通过对比试验发现,不同组织形貌的AlTiC中间合金细化工业纯铝时具有明显不贩细化效果,AlTiC呈块状分布的AlTiC中间合金细化效果最好,其次是TiAl3呈梅花状和片状分布的AlTiC中间合金。借助金相显微镜、X射线衍射仪手段对其组织进行了分析对比,探讨了组织遗传对细化效果的影响,分析表明：3种AlTiC中间合金的相组织相同,均由αAl基体、TiAl和TiC组成,细化效果的差异由AlTiC中间合金的组织遗传效应造成的。     

温度对AlTiC中间合金内部组织及细化性能的影响

采用接触法来制备AlTiC中间合金.通过X-ray衍射和SEM扫描电镜及EDS能谱分析发现,随着温度的改变,TiC和Al3Ti粒子的形态和分布会发生相应的变化,而TiC和Al3Ti粒子的形态和分布的变化很大程度上影响着AlTiC中间合金的细化效果.研究结果表明:在800℃时,AlTiC中间合金对工业纯铝的细化效果最好.     

Production of Al–Ti–B grain refining master alloys

Abstract

In the present work the interfacial phenomena observed when an Al-Ti-B master alloy is produced have been studied using a modified sessile drop technique.The effect of emulsification has been demonstrated and the influence of small levels of CaF₂ and MgF₂ seen. The Al-Ti-B master alloys were made by the addition of potassium fluotitanate, K₂TiF₆, and potassium fluoborate, KBF₄, to molten aluminium at 750°C. The product was an Al-5Ti-1B(wt-%) master alloy and a KF-AlF₃ flux of eutectic composition. Problems can occur with the production of such alloys by first, emulsification of the liquid Al-Ti-B alloy and KF-AlF₃ flux and second, agglomeration of titanium diboride particles by the wetting and engulfment of the KF-AlF₃ flux. It has been found that levels of CaF₂ and MgF₂ in the fluoride salts greater than 50 ppm and 70 ppm, respectively, can prevent the above emulsification and boride agglomeration occurring.     

Effects of processing parameters on aluminide morphology in aluminium grain refining master alloys

Abstract

An investigation has been made of the effects of processing parameters on the microstructure of Al–Ti and Al–Zr alloys produced by the reduction of potassium fluorotitanate and potassium fluorozirconate by aluminium. Blocky aluminides (TiAl₃ and ZrAl₃ respectively) are produced when the reduction is performed in the liquid+solid phase region and flaky aluminides are produced when it is performed in the liquid phase region. The use of Na₂TiF₆ rather than K₂TiF₆ has no apparent effect on the alloy structure. The microstructure and the size of aluminide blocks or flakes produced are further influenced by the subsequent cooling rate experienced by the alloy. Post-fabrication heat treatment of Al–5Ti–0·2B (wt-%) alloys (produced by combined reduction of potassium fluqrotitanate and potassium fluoroborate by aluminium) causes boride particles to precipitate on the aluminide surfaces. These borides grow in size and decrease in number with heat treatment time.

MST/1355     

Influence of zirconium on grain refining efficiency of Al–Ti–C master alloys

The influence of Zirconium on the grain refinement performance of Al–Ti–C master alloys and the effect mechanism has been studied in this paper. The experimental results show that Zr not only results in poisoning the Al–Ti–B master alloy, but also poisons the Al–Ti–C master alloys. The poisoning effect is more obvious at higher melting temperature. When 0.12%Zr is added into the melt, the grain refinement performance of Al–5Ti–0.4C refiner with 0.2% addition level absolutely disappears at 800 °C. The experimental results also show that it is difficult to refine the commercial purity Al containing 0.15%Zr by Al–5Ti–0.4C master alloy. Further experiments show that the Zr element can interact with both TiAl₃ and TiC phases. If both of them are present, Zr preferentially reacts with TiAl₃ phase.     

Microstructure and grain refining performance of Al–5Ti–1B master alloy prepared under high-intensity ultrasound

The microstructure and grain refining performance of an Al–5Ti–1B master alloy prepared under high-intensity ultrasound were investigated. With applying continuous high-intensity ultrasound vibrations in the reaction, the Al–5Ti–1B master alloy is successfully manufactured in 4 min. Compared with conventional Al–5Ti–1B master alloys, the mean size and the size spread of TiB₂ particles in the prepared master alloy are evidently decreased. The narrower particle size spread significantly improves the grain refining performance of the master alloy, which proves the calculation predictions by Greer. Consequently, the limiting grain size of commercial purity aluminium refined by the new master alloy can reach 45 μm.     

Al含量对热爆合成Al-Ti-C组织及细化性能的影响

为改善Al-Ti-C中间合金的晶粒细化性能,采用铝液中热爆合成法制备出用于铝及铝合金晶粒细化的Al-Ti-C中间合金.通过DTA、XRD和SEM等手段分析了Al含量对热爆反应过程及合成产物组织形态的影响,并比较了Al-Ti-C中间合金对工业纯铝的细化效果.结果表明,铝液中热爆合成的Al-Ti-C中间合金由Al、Al3Ti、TiC三相组成,Al含量对反应体系的合成温度、反应速度及合成产物组织产生重要影响.调整原料Al含量可有效控制中间合金中第二相粒子组织形态,获得良好的晶粒细化性能.     

Performance of AlTi5B1, AlTi3B3 and AlB3 master alloys in refining grain structure of aluminium foundry alloys

Abstract

The capacity of AlTi5B1, AlTi3B3 and AlB3 grain refiners to refine the grain structures of AlSi7Mg and AlSi11Cu2 foundry alloys was investigated. The performance of AlTi5B1, well established to be the best grain refiner for wrought aluminium alloys, is not nearly as good with the AlSi7Mg and AlSi11Cu2 alloys. Relatively smaller grains are obtained with the AlTi3B3 grain refiner in both alloys. The AlB3 grain refiner, on the other hand, improves the grain structure only as much as the AlTi5B1 grain refiner does. With as much as 0·04–0·1 wt-%Ti, the commercial alloys cannot enjoy the outstanding potency of the AlB₂ particles since the B supply is readily transformed to TiB₂ particles. However, the grains of the Ti free AlSi7Mg and AlSi11Cu2 alloys (～0·005 wt-%Ti) are very small and nearly globular for the entire range of holding times when inoculated with AlB3, implying not only a remarkable grain refining capacity but also a strong resistance to fading of the grain refinement effect. The lack of Ti in the melt allows the entire B to form AlB₂ particles, the perfect substrates to promote the nucleation of α-Al crystals. Aluminium castings can enjoy grain sizes well below 200 μm, with an addition of 0·02 wt-%B, provided that they are Ti free. That the potent substrates are made available just before the nucleation of α-Al crystals avoids fading effects and is a further advantage of the AlB3 grain refiner in recycling operations.     

Microstructure and dispersion of Cu-TiC X master alloys into molten Cu and the relation to contact angle data

Cu-TiC _x composites have been made self-propagating high temperature synthesis of Cu-Ti-C mixtures. It was found that as the C/Ti ratio decreases, wetting of the carbide, by what is effectively a molten Cu-Ti alloy, is improved and the distribution of the carbides in the master-alloy becomes ideal for subsequent dispersion, i.e. discrete particles are formed. Increasing quantity of Cu in the reactants from 10 to 50 wt% Cu had a similar effect to decreasing the C/Ti ratio and enabled the size of the TiC _x particles to be varied in the approximate range 20–0.5 μm. Incorporation and dispersion of the master alloy into molten copper was possible when the C/Ti ratio in the products was below approximately 0.73, which agreed well with contact angle data in the literature.     

Investigation of the grain refining performance of Al-5Ti-1B master alloy on the recycling process of A356 alloy

In this paper, the grain refining performance of Al-5Ti-1B master alloy on the recycled A356 alloy is investigated using the macrostructure examination and chemical analysis. Results show that Al-5Ti-1B is composed of the dispersion of blocky TiAl₃ particles and mixtures of small TiAl₃ and TiB₂ particles. Both particles refine grain structures of A356 alloy. As the initial recycling process proceeds, A356 alloy still exhibits fine structures. However, during the subsequent recycling process, the grain size of A356 alloy become larger. The concentration of titanium and boron decreases with increasing the number of recycling, especially in the subsequent recycling process. It is proposed that recycling of refined A356 can best be conducted in the initial recycling process and then additional grain refiner needs to be added to maintain the grain refining performance for the continuous recycling process of A356 alloy.     

材料的组织结构对锌电极电化学行为的影响

在对锌多晶进行变形、退火等方式处理的基础上,运用金相分析法、X射线衍射法、循环伏安法等方法,分析了金属锌的组织结构与电化学性能的关系。结果表明,锌单晶(002)晶面电极的氧化还原可逆性优于锌单晶(100)晶面电极,锌单晶(100)晶面电极的氧化和还原能力优于锌单晶(002)晶面电极;锌多晶电极的氧化性能和还原性能优于锌单晶电极;晶界、位错等缺陷会提高锌的溶解速度,同时电极表面的位错对还原过程中锌原子的沉积有利;晶粒的增大会减小晶界面积,使得锌电极的晶间腐蚀等局部腐蚀加剧,降低锌电极的耐蚀性,但是晶粒大小对电极电化学性能的影响相对于位错及其它缺陷要小得多。     

Evaluation of inoculant efficiency in Al grain refining alloys

It has been shown that the DET can be used to produce powder samples of grain refining master alloys that contain isolated inoculant particles of variable catalytic potency, as shown in Figure 3. The effectiveness and subsequent identification of inoculant particles in terms of their ability to produce grain refinement in bulk Al casting can also be distinguished by combining the DET with an interrupted nucleation quenching treatment during DTA. This quenching treatment allows for identification of potent inoculants by preserving droplet solidification microstructures associated with the nucleation and growth of Al from the effective particle population, also shown in Figure 3. The ability to separate droplets containing potent inoculant species allows for examination and comparison of discrete inoculant characteristics such as intermetallic morphology. In addition, because this quenching treatment is performed at a known measured temperature, the potent inoculant population is characterized by a discrete heterogeneous nucleation response. The initial results of this study indicate that the DET used in conjunction with analytical x-ray and electron beam studies provides chemical and structural information about effective inoculant particles (14). Moreover, influential parameters which may hamper or accentuate the nucleation of grains by a statistical minority of inoculant particles can now be assessed in master alloy droplets and used to develop more effective catalyst particles.     

"绿色”高效Al -Si合金变质剂--Al-P中间合金

为了解决Al-Si变质过程中的环境污染问题,用熔铸法制备了一种高效,低价格且适于产业化生产的Al-Si合金变质剂－Al-P中间合金,该中间合金w(P)可达到2．0％－5．5％,对共晶和过共晶（含Si量12％－24％）成分的Al-Si合金进行变质,加入0．3％－0．8％的Al-3P中间合金即得良好的变质效果,使其初晶Si数量明显增多,平均晶粒尺寸分别下降到30μm和50μm以下,该中间合金使用工艺简便,可在低温下加,而且无污染,无反应渣,变质效果长效稳定,易储存、使用综合成低,克服了当前变质的缺点,可以实现Al-Si合金的“绿色”变质,有着广阔的应用前景。     

Segregation of solutes in Al-Ni and Al-Sn alloys and its influence on their mechanical properties

A study was made of the intensity of scattering of monochromatic X-rays at small angles from Al-3.6 at. % Ni and Al-0.26 at. % Sn solid solutions, in order to determine if the solutes are really dispersed. Electron-microscopic examinations were also carried out. Both alloys were obtained by rapid quenching from the melt in order to obtain the optimum dissolution. However, perfectly homogeneous solid solutions were not obtained, but agglomerations of solute atoms were detected. The evolution of clusters during annealing was examined. Their influence on microhardness and microstrain properties is discussed.     

Microstructure and properties of melt-quenched TiNi-based alloys

Titanium-nickel (TiNi) based alloys doped with hafnium and copper have been obtained by melt-jet spinning at a cooling rate of 10⁵–10⁶ K/s. The melt-spun ribbons have been studied by the electron — microscopy and X-ray diffraction techniques. It is established that, depending on the content of doping elements and cooling rate, the alloys occurred in an either amorphous or mixed amorphous-crystalline state. Mechanical properties of the obtained alloys have been measured.     

Microstructure and properties of burn-resistant Ti-Al-Cu alloys

Ti-Al-Cu series burn-resistant alloys are newly developed materials which have low density, low cost and are easy to process. The results show that Ti-Al-Cu alloys have good burn resistance due to their good thermal conductivity, low melting point, and the existence of Ti₂Cu phase which also has a very low melting point. Ti-Al-Cu alloys have excellent thermal processability and good room and high temperature tensile properties, but an increase in copper content harms their thermal stability. After thermal exposure for a long time, Ti₂Cu phase will coalesce and coarsen, but the addition of Si and Al will be useful for their thermal stability. The Ti-13Cu-1Al-0.2Si alloy has good thermal stability at 540°C and good creep resistance at 300°C and 100 MPa. The phases of Ti-Al-Cu alloys were found to be composed of phase and Ti₂Cu. The character of the Ti₂Cu phase changes with the increasing copper content.     

全再生细骨料的制备及其对混凝土性能影响的试验研究

传统再生细骨料的需水量大、强度低,较难利用。将废弃混凝土全部破碎成细骨料的全再生细骨料技术能够有效提高再生细骨料的性能。在前期研究的基础上,进行了全再生细骨料的制备及其对混凝土性能影响的研究。研究结果表明,全再生细骨料的制备应包括破碎、筛分和整形工艺;全再生细骨料中小于0.075和0.15mm的细粉对其强度性能有利,不宜去除;考虑到其细粉组成包括石粉,其微粉含量限值可较现有标准有所提高。全再生细骨料相对于传统再生细骨料在性能上有很大改善,胶砂需水量小且强度高,以其配制的C30和C50混凝土性能明显优于传统再生细骨料。全再生细骨料的胶砂需水量等性能仍不如机制砂和河砂,但其胶砂强度却高于机制砂和河砂;以其配制的混凝土抗压强度(特别是高水胶比时)明显高于河砂和机制砂混凝土,但工作性能略低。综合来看,全再生细骨料能够全取代河砂和机制砂用于制备C30和C50混凝土。