Refining Effect of a New Al3Ti1B1RE Master Alloy on Al Sheets Used for Can Manufacture and Behavior of Rare Earths in Master Alloy

The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the refining effect of the refiner on the material has superiority over foreign or domestic Al5Ti1B refiner, and the refiner still retains its refining ability for 6 h after adding it to molten Al, thus improving the strength and plasticity of the material remarkably. The excellent refining effect and stability of AlTiBRE refiner result from that RE can lower the surface energy of molten Al and improve the wetting characteristics of molten Al on refinement nuclei such as TiAl 3, TiB 2, etc., thus giving full play to the effect of heterogeneous nucleation and impeding the congregating tendency of TiB 2 phase in molten Al. At the same time, RE gathering in front of solid/liquid interface are also easy to cause composition supercooling in molten Al, thus impeding the growth of α Al grains and promoting α Al nucleation on refinement nuclei. In addition, RE also play certain role in purification and grain refinement, or modification, especially their effect of purification can improve the metallurgical quality of AlTiBRE master alloy.

INFLUENCE OF Al-5Ti-1B MASTER ALLOY ON MICROSTRUCTURE AND DAMPING CAPACITY OF ZA27 ALLOY

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Influence of Al-5Ti-1B master alloy addition on the grain size of AZ91 alloy

The mechanical properties of castings depend on the grain size.There is evidence that titanium and boron(Al-5Ti-1B master alloy)affect the grain size of magnesium alloys.Here,the influence of the addition of 0-1 wt.%of Al-5Ti-1B master alloy on the grain size of AZ91 magnesium alloy was investigated.Melting of the alloy was performed in steel and corundum crucibles.To study the effect of cooling rate on grain size,cylindrical samples were cast in steel and fireclay molds.The Al-5Ti-1B master alloy addition did not change the phase composition of the AZ91 alloy.This study demonstrates that the addition of Al-5Ti-1B did not contribute to the grain refinement of the AZ91 alloy,but rather led to its coarsening for samples cast in both the steel and fireclay molds.Increasing the holding time after the addition of the Al-5Ti-1B master alloy from 15 to 110 minutes also did not lead to significant grain coarsening.The mechanical properties of the AZ91 alloy samples slightly improved after Al-5Ti-1B addition.

Effect of Al5Ti1B master alloy on microstructures and properties of AZ61 alloys

AZ61 alloys with different levels of Al5Ti1B master alloy additions were prepared by conventional casting method.The effects of Al5Ti1B contents and holding time on microstructures and microhardness of AZ61 alloys were studied by XRD,OM and microhardness testing techniques.The results show that when the addition level of Al5Ti1B master alloy is less than 0.5%(mass fraction),the average grain size of the alloys decreases with the increase of Al5Ti1B content at the same holding time.But the grain size increases somewhat with further addition of Al5Ti1B.The average grain size of the alloys decreases with the increase of the holding time as it is less than 30 min at the same addition level of Al5Ti1B.It is considered that TiB2 particles can serve as the heterogeneous nucleation sites ofα-Mg during solidification,and heterogeneous nucleation is the main reason for the grain refinement of AZ61 alloys.The microhardness of the refined AZ61 alloys with 1.0%Al5Ti1B addition is increased by about 8%.

Structural heredity between Al5Ti1B and AlTi, AlB master alloys

Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master alloy and the boride phases depend on AlB master alloy. There are remarkable structure heredity between Al5Ti1B master alloy and AlTi, AlB master alloys. Theoretical analyses show that AlTi and Al-B master alloys can change the melt structure of Al5Ti1B master alloy, then affect the solid structure of the master alloy.

Effects of solid deformation and melt vibration on structure and refining performance of Al5Ti1B master alloy

Grain refinement can offer significant benefits to both continuous casting and cast to shape products, and Al5Ti1B master alloy containing mainly TiAl 3 and TiB 2 particles in Al matrix has been proven to perform well for giving the best refinement, but the working method of adding Al5Ti1B rod to the furnace during casting are often related to solid deformation, and melt vibration may help to reduce the size of TiAl 3 and improve the distribution of TiB 2. Therefore the effects of solid deformation and melt vibration on the structures and refinement performance of Al5Ti1B master alloys were studied. The experimental results show that both solid deformation and melt vibration can improve the distribution of TiB 2 in Al5Ti1B master alloys, increase the interface energy and nucleation activity of TiB 2 particles. In the meantime, solid deformation can store deformation energy and melt vibration can break fragile plate like TiAl 3 compounds. So both methods can improve the refinement effectiveness of Al5Ti1B master alloys.

Grain refining effect of Mg by novel particle cluster-containing Al-Ti-C master alloy

A novel A1-Ti-C master alloy containing A14C3 and TiC particle clusters, which exhibits great refining potential for Mg, was prepared. With the addition of 2% A1-Ti-C master alloy, the grains transform to equiaxed crystal with a diameter of （110-a：17） ~tm. The results indicate that A14C3 and TiC particle cluster, rather than a single particle, plays an important role in the refining process. Compared with the simplex smooth nucleating substrate, concave regions on the particle cluster provide easier route for the transformation from liquid Mg atoms to stable nucleus. Nucleus with a small size can also reach the critical nucleation radius when they attach on the concave regions of the substrate. A14C3 and TiC particle clusters thus become more favorable nucleating substrate for a-Mg grains.

Effect of AlP master alloy on grain refinement of primary silicon in eutectic Al-Si alloys

To obtain the finer primary silicon crystals, the proprietary Al-P masteralloy was adopted to modify the eutectic Al-Si alloys and the most suitable modification process wasmade in the experiments. The SEM (Scanning Electron Microscope) and DSC (Differential ScanningCalorimeter) analysis indicate that the Al-P modifier has more advantages over Cu-P and Fe-Pmodifier in easily addition, no elemental alteration and less undercooling of primary silicon'ssolidification, which suggests the Al-P master alloy is an effective modifier of eutectic Al-Sialloys.

Experimental and first-principles investigation of crystal structure of powder metallurgy Al-1.1Sc and Al-2Sc alloys

Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice parameters, the mechanical properties of the alloys were calculated theoretically with WIEN2k and EMTO programs, respectively. The elasticity moduli of the experimentally produced alloys were compared with the theoretical calculation results. The calculated mechanical properties of A13Sc phase and A1-Sc alloys were discussed to determine the optimum Sc content of Al-Sc alloys. It may be concluded that the Sc content should be the maximum about 1.0%, much more Sc addition could not improve the mechanical properties of the alloys.

Al-5% Ti-1% B对Sr变质Al-13.0 %Si合金组织影响的研究

Sr作为变质剂加入到Al Si合金中能导致共晶硅的形态从粗大的片状 (或称为针状 )转变为细小的纤维状 ,但同时也促进了柱状枝晶的形成。当Al 5%Ti 1%B加入量低于 0 8%时 ,α枝晶有等轴化趋向 ,柱状枝晶的主干长度缩短 ,对共晶硅的形态与尺寸没有显著的影响 ,尽管共晶团尺寸略有下降。但当Al 5%Ti 1%B加入量超过 0 8%后 ,其对Sr变质作用的有害影响显现出来 ,α Al枝晶数量减少 ,出现初晶硅 ,共晶硅尺寸变大。随着加入量进一步增加 ,最终转变为未变质组织。所有的结果表明 :熔体中有效Sr量随着Al 5%Ti 1%B中间合金加入量的增加而降低 。

高品质Al-5Ti-1B合金线的组织与晶粒细化性能

采用等离子体发射光谱仪、光学显微镜、X射线衍射仪和扫描电镜,研究了高品质Al-5Ti-1B合金线的化学成分、显微组织和晶粒细化性能。结果表明,高品质Al-5Ti-1B合金线的Ti、B合金元素含量稳定,Fe、Si、V、K杂质元素含量低。合金线的组织均匀细小,无氧化夹杂物,TiAl3相平均尺寸为16.7μm,TiB2粒子平均尺寸为0.73μm。添加质量分数为0.2%的高品质Al-5Ti-1B合金线可使纯铝铸态晶粒细化到75.7μm,晶粒细化响应时间块,抗衰退能力强,适应铝熔体温度范围宽。研究结果可为细化剂生产企业和铝加工企业在生产、选用高品质Al-5Ti-1B合金线时提供参考。

核级Zr-1Nb铸锭中Nb元素均匀性控制

针对Zr-1Nb铸锭中Nb元素含量范围窄（0．9％～1．1％），对成分均匀性要求高，且易形成Nb高密度夹杂（HDI）等技术难题，研究了铌元素的添加方式以及真空自耗电弧熔炼工艺参数对Nb成分均匀性的影响。结果表明，以ZrNb中间合金为配料，采用合理的熔炼工艺，可获得无偏析、无HDI冶金缺陷、成分均匀性优良的合金铸锭。

Optimization of processing parameters for preparation of Al-3Ti-1B grain refiner

Al-3Ti-1B master alloys were prepared at different processing parameters by the reaction of halide salts,and the grain refining response of Al-7Si alloy was investigated with Al-3Ti-B master alloy.The microstructure of master alloy and its grain refining effect on Al-7Si alloy were investigated by means of OM,XRD and SEM.Experimental results show that,the size of Al3Ti particles presented in Al-3Ti-1B master alloys increases with the increase of reaction temperature and decreases with the increase of cooling rate.The grain refining efficiency of Al-3Ti-1B master alloy on Al-7Si alloy is mainly attributed to heterogeneous nucleation of Al3Ti particles,and the morphology ofα(Al)changes from coarse dendritic to fine equiaxed.As a result,Al-3Ti-1B master alloy is prepared by permanent mold,and holding at 800 ℃for 30min,which has better grain refining performance on Al-7Si alloy.

Constitutive equation and hot processing maps of Al-5Ti-1B master alloy

The isothermal compression tests of A1-5Ti- 1B master alloy were conducted on the thermal mechanical simulator Gleeble-1500D at the deformation temperature range of 300-450 ℃,the strain rate range of 0.01- 10.00 s^-l, and the engineering strain of 50 %. The effects of deformation temperatures and strain rates on the flow stress were analyzed by the true stress-true strain curves. The result indicates that the flow stress increases with the increase of strain rate, while it decreases with the increase of temperature. The hot deformation activation energy of A1-5Ti-IB master alloy is calculated to be 250.9 kJ.mol^-1, and the constitutive equation is established as ε=1.97 x lO^19[sinh（O.O15δ）^11.14exp（-250.9/RT）, and the validity of this constitutive equation is verified. Based on dynamic material model （DMM） criterion, the hot processing map of AI-5Ti-1B master alloy is obtained. The optimum hot extrusion conditions are determined as deformation temperature of 400℃ and strain rate of 1.00 s^-1, and the flow instability only appears at the temperature range of 300-340℃ at the base of the hot processing map.

中间合金对A356.2合金细化的效果

采用铝业协会制订的 ＴＰ－１型标准测试法，对 Ａ１－１０ＲＥ、Ａ１－５Ｔｉ－１Ｂ、Ａ１－５Ｔｉ－１Ｂ－１０ＲＥ等中间合金对 Ａ３５６． ２合金的细化效果进行评价，以优化铝合金轮毂制造过程中合金熔体细化处理工艺。结果表明，Ａ１－５Ｔｉ－１Ｂ－１０ＲＥ中间合金中的ＲＥ不仅可以有效抑制晶粒尺寸的衰退，而且在一定程度上改善Ｔｉ、Ｂ、Ｓｒ对Ａ３５６．２合金显微组织的细化和变质效果；ＴＰ－１型晶粒度检测法是一种简单、直观、准确的中间合金细化效果在线评价方法。