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.

Grain refinement of Al-3.5FeNb-1.5C master alloy on pure Al and Al-9.8Si-3.4Cu alloy

The refinement potential of Al-3.5 Fe Nb-1.5 C master alloy on pure aluminium and Al-9.8 Si-3.4 Cu alloy has been investigated. Different amounts of Al-3.5 Fe Nb-1.5 C master alloy were added to estimate the optimal addition level. It was found that the addition of Al-3.5 Fe Nb-1.5 C grain refiner can promote significantly the refinement of grains in the pure aluminium, particularly at 0.1 wt.%, with the mean primary aluminium α-grain size reducing to 187±3 μm from about 1-3 mm. Similarly, the microstructural study of the Al-9.8 Si-3.4 Cu alloy die casting at different weight percentages(viz. 0.0 wt.%, 0.1 wt.% and 1.0 wt.%) of Al-3.5 Fe Nb-1.5 C master alloy shows that the Al-3.5 Fe Nb-1.5 C master alloy as a grain refiner is also acceptable for Al-Si cast alloys when the silicon content is more than 4 wt.%. As a result of inoculation with Al-3.5 Fe Nb-1.5 C master alloy, the average grain size of α-Al is reduced to 22±3 μm from about 71±3 μm and grain refining efficiency is not characterized by any visible poisoning effect, which is the major limitation in the grain refinement of Al-Si cast alloys by applying Al-Ti-B ternary master alloys. Mechanical properties such as ultimate tensile strength and yield strength are significantly improved by 9.6% and 9.7%, respectively.

Al-3B中间合金添加量对再生铸造铝合金中杂质铁含量的影响

采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)和直读光谱仪等分析测试方法研究A1-3B中间合金添加量对再生铝合金A356中杂质铁含量的影响。结果表明:经过净化后再生铝合金中铁含量随着A1-3B合金添加量的增加而降低,同时晶粒也得到了细化。当A1-3B中间合金添加量为3%(质量分数)时,铁含量从0.96%降低到0.68%,除铁率为29.1%,再生铝合金A356的抗拉强度和伸长率分别提高了20.5%和38.6%。再生铸造铝合金中铁含量降低的主要原因是A1-3B合金的B元素和再生铝合金A356中的Fe反应生成Fe_2B沉于炉底。

Al3Ti4B中间合金对Mg-7Al-0.4Zn-0.2Mn合金显微组织和性能的影响

研究了Al3Ti4B中间合金对 Mg 7Al 0.4Zn 0.2Mn合金的显微组织、力学性能及耐腐蚀性能的影响。结果表明: 当Al3Ti4B加入量小于0.3%(质量分数)时, 合金的平均晶粒尺寸显著减小; 当 Al3Ti4B加入量为0.3%时, 合金组织显著细化, 平均晶粒尺寸由未变质合金的 135μm细化到 30μm, 合金拉伸力学性能和耐腐蚀性能最好; 当加入量超过0.3%时, 晶粒粗化; 具有密排六方结构的高熔点化合物 TiB2 (θm =2 980 ℃)和 AlB2(θm=980℃)均可作为α Mg的异质核心, 大量异质结晶核心的存在是导致α Mg晶粒细化的主要原因。

Al-3B中间合金对亚共晶Al-Si合金的晶粒细化机制(英文)

Al-3B中间合金是亚共晶Al-Si合金的高效细化剂之一。实验研究了Al-3B中间合金中未溶AlB2颗粒对Al-7Si合金晶粒细化的影响。结果表明,AlB2颗粒的数目和沉降对晶粒细化效果都有重要影响。在实验结果和理论分析基础上,提出了Al-3B中间合金对亚共晶Al-Si合金晶粒细化的新机制,认为通过共晶反应形成的"Al-AlB2"包覆结构是导致晶粒细化的直接原因,未溶的AlB2颗粒是α(Al)相的间接行核基底。

Al-3B对亚共晶Al-Si合金的晶粒细化作用

从热分析角度研究Al-3B对Al-7Si的晶粒细化作用,B对Al-7Si晶粒细化的最佳加入量为0.03%。考察了Al-3B对不同Si含量亚共晶铝硅合金的晶粒细化作用,B对高硅含量亚共晶铝硅合金的晶粒细化效果更好。分析了B对亚共晶铝硅合金的细化机理,认为Al-B共晶理论可以有效解释试验现象。

Ni_3Al-0.2B金属间化合物的熔盐热腐蚀

本文应用电化学方法及物相分析技术研究了Ni_3Al-0.2B金属间化合物在熔融NaCl-(Na,K)_2SO_4中的腐蚀.发现Ni_3Al-0.2B耐熔盐热腐蚀能力极差,硫化-氧化是腐蚀破坏的主要原因.Ni_3Al-0.2B中添加6at.-％Cr,0.5at.-％Zr加速了材料的腐蚀。

稀土对Al-Ti-B合金中Al_3Ti颗粒形貌的影响

在工业Al-5Ti-1B中间合金的重熔稀释过程中添加稀土元素,采用光学显微镜观察了Al_3Ti相的分布和形貌,并用能谱仪进行了微区线扫描成分分析。结果表明,在900℃时加入稀土可明显改善Al_3Ti相的形貌,并改善Al_3Ti颗粒在金属基体上的分布,在850℃时加入稀土会产生少量的针状Al_3Ti相,而在950℃时加入稀土,Al_3Ti相则全部为针状;同时,通过线扫描分析发现,稀土元素包覆在Al_3Ti周围,阻止了Al_3Ti相的长大,细化了Al_3Ti的尺寸。

微量B对Mg-3Al-1Zn镁合金组织和性能的影响

B通过Al-3B中间合金加入Mg-3Al-1Zn合金中,利用OM、XRD及力学性能测试、极化曲线测定等手段对不同B加入量合金的组织和性能进行了分析。实验结果表明,合金的组织随着B加入量的增加变得粗大,当B加入量为0.05%时出现粗大枝晶,0.1%时枝晶进一步长大且出现二次枝晶。合金的力学性能和耐腐蚀性能也随B加入量的增加而降低。

Al-3Ti-3B对A356合金的细化作用

采用Al-3Ti-3B合金做A356合金细化剂,分析冷却速度、保温时间对Al-3Ti-3B细化作用的影响,并与Al-5Ti-1B合金进行比较。结果表明:锥形试样不同直径处,Al-3Ti-3B合金细化效果无明显差异,Al-3Ti-3B对冷却速度的敏感性小于Al-5Ti-1B。随时间延长,Al-5Ti-1B细化效果有明显的衰退。Al-3Ti-3B细化剂在120min内,晶粒尺寸变化不大,细化剂抗衰退性很好。在变质和细化处理后,Al-3Ti-3B对硅形态的影响较大。

Co含量对Fe-30Ni-xCo-10.5Al-3Nb-0.05B形状记忆合金组织与伪弹性的影响

熔炼了Fe-30Ni-xCo-10.5Al-3Nb-0.05B(x=0、9、18、22,原子分数,%)多晶合金,将合金冷轧后进行固溶和600℃下的时效处理,时效时间为60 h。应用扫描电镜、X射线衍射仪研究了合金组织和物相的变化,并对合金进行了室温下的硬度和伪弹性测试。结果表明:Co含量为0%时,时效后晶内析出γ’和β两相;Co含量为9%~22%时,时效后晶内析出单一的γ’相;随着Co含量的增加,合金晶粒大小逐渐增加,γ’相的粒径也会发生变化。Co含量为0%的合金表现出超弹性,最大可回复应变为5.87%;Co含量为9%~22%的合金表现出伪弹性,其中,Co含量为18%的合金伪弹性最佳,形状回复率达84.00%,可回复应变达5.25%。合金的应力-应变曲线显示,合金伪弹性的来源除了应力诱发的马氏体相变,还存在其它机制。

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.

ZL101铝合金熔体旋转磁场及Al-3B细化处理效果比较研究

采用智能温度记录仪、金相显微镜、拉伸试验机,分别研究了旋转磁场和Al-3B细化剂处理对ZL101铝合金熔体凝固过程、显微组织及力学性能的影响。对比结果显示,在ZL101铝合金中添加Al-3B细化剂,随细化剂中B含量增大,α(Al)的平均晶粒尺寸先减小后增大,抗拉强度和伸长率先增大后减小,当Al-3B细化剂B含量达到0.06%时细化效果最优,抗拉强度和伸长率分别提高9.4%和34.9%。用旋转磁场细化ZL101铝合金熔体时,随旋转磁场电流参数增大,α(Al)的平均晶粒尺寸先减小后增大,抗拉强度和伸长率先增大后减小,最优参数电流为80A、频率为8 Hz,抗拉强度和伸长率分别提高10.5%和37.2%。采用最佳含量Al-3B细化剂和最优参数旋转磁场对同一成分的ZL101铝合金熔体进行细化处理效果对比表明,旋转磁场处理效果优于细化剂细化效果。

Effect of Gd on microstructure and refinement performance of Al-5Ti-B alloy

Al-5Ti-B and Al-5Ti-B-Gd master alloy refiners were fabricated by fluorine salt casting method.The microstructure and phase constitution of the master alloys were investigated by scanning electron microscopy (SEM),transmission electron microscopy (TEM) and X-ray diffraction (XRD).The results show that Al-Ti-B alloy refiner consists of Al_(3)Ti phase and TiB2 phase.After Gd is introduced into the intermediate alloy,Ti_(2)Al_(20)Gd phase appears in the alloy,the size of Al_(3)Ti is significantly reduced,and Ti-Al-Gd phase is found in the edge of Al_(3)Ti phase.At the same time,some independent Ti-Al-Gd phases appear in local areas,which are Ti_(2)Al_(20)Gd phase determined by micro-area electron diffraction analysis.Analysis and calculation results of the high-resolution images of the Ti_(2)Al_(20)Gd/Al structure show that there is no other compound at the junction between the Ti_(2)Al_(20)Gd phase and Al,and Ti_(2)Al_(20)Gd phase has a great difference in atomic space with the α-Al,which cannot be directly used as heterogeneous nucleus.But,after being decomposed in the aluminum melt,the Ti_(2)Al_(20)Gd phase can promote the refinement effect of the refiner.In the Al-Ti-B-Gd master alloy,there are many dispersed Al_(3)Ti particles with a size of less than 1 μm,which can promote the Al-5Ti-B refining effect.

Effects of Si Content and the Addition Amount of Al-3B Master Alloy on the Solidification Structures of Hypoeutectic Al-Si Alloys

Effects of Si content and the addition amount of Al-3B master alloy on the solidification structures of hypoeutectic Al-Si alloys were studied. The addition amounts of the master alloy were 0.2%, 0.4%, 0.7% and 1% (mass fraction, so as the follows), respectively. The Si content of Al-Si binary alloys investigated varied from 1% to 11%. The observation of macrostructures of non-refined samples showed that 3% Si constitutes a transition point at which the minimum grain size can be obtained. It was also found that Al-3B master alloy can shift the transition point towards a higher Si value when its addition amount increases, making this point appear at 4%, 5% and 6% Si as its addition amount increases up to 0.4%, 0.7% and 1%, respectively.

HOT CORROSION OF Ni_3Al-0.2B IN MOLTEN NaCl-(Na,K)_2SO_4

Hot corrosion of intermetallic compound Ni_3Al-0.2B was studied by electrochemical techniques combined with physical analyses.It was found that hot corrosion resistance of Ni_3Al-0.2B is rather inferior.Sulfidation-oxidation is responsible for the accelerated corrosion.The addition of 6at.-% Cr and 0.5at.-% Zr to Ni_3Al-0.2B may accelerate its corrosion.

Enhancement of TiB Grain Refining Effect on A356 Gravity Die Casting with the Addition of Yttrium

The present work investigates the effect yttrium on the grain refining efficiency of Al-5Ti-1B in gravity die cast A356 aluminum alloy. A series of casting experiments were carried out in which the Ti and B contents were maintained constantly at 0.1 and 0.02 wt% respectively. The inoculation level of yttrium was manipulated at the amount of 0, 0.1, 0.2, 0.3, 0.4 and 0.5 wt%. Microstructural characterization of the as-cast A356 alloy was investigated by means of optical microscope and its phases are detected by XRD. XRF is used to determine the contents of inoculating elements such as Ti, B and Y so that their actual optimal ratio in the casting can be approximated. The mechanical properties tested are tensile strength and hardness. The inoculation of yttrium was found to enhance the grain refinement effect of Al-5Ti-1B grain refiner and improve the mechanical properties. The optimal weight percentage of yttrium was discovered to be 0.3. The grain refining efficiency of combining yttrium and Al-5Ti-1B on A356 aluminum alloy was mainly attributed to the heterogeneous nucleation of TiB2 and TiAl3 particles which were dispersed more evenly in the presence of yttrium and also as a result of α-Al grain growth restriction by AlY3compound precipitated at grain boundaries during solidification.

Al-5.22Ti-1.65B的金相组织对ZL101A铸造铝合金的影响

分析了Al-5.22Ti-1.65B中间合金的金相组织对ZL101A铸造铝合金的影响,结果表明:在Al-5.22Ti-1.65B中间合金的金相组织中,Ti Al3相呈块状,分布于α-Al基体上,Ti B2颗粒为球状,处于Ti Al3相之间。经过Ti Al3相和Ti B2颗粒分布均匀的铝钛硼中间合金处理后,减少了树枝状α-Al相的形成,共晶硅的分散性更好,使ZL101A铸造铝合金的组织变得更均匀。

硼对Mg-7Al-0.4Zn-0.2Mn合金组织及性能的影响

研究了B对Mg-7Al-0.4Zn-0.2Mn合金显微组织和力学性能的影响。结果表明:加入微量的B就能使合金的晶粒得到显著的细化,并且随着B加入量的增加,细化效果越明显,当B的加入量(质量分数,下同)为0.15%时,平均晶粒尺寸由未变质合金的约140μm细化到约40μm。分析认为:具有密排六方结构的高熔点化合物AlB2可作为α-Mg的异质核心,从而细化镁合金晶粒。微量B的加入使铸态合金的力学性能得到不同程度的提高,当B的加入量为0.15%时,合金的显微硬度、抗拉强度和屈服强度分别比未变质合金提高13.1%、19.5%和22.0%,冲击吸收功约为未变质合金的2.3倍。B的加入量为0.10%时,合金的伸长率比未变质合金提高21.6%。

亚共晶Al-Si合金的细化处理

比较了Ａｌ－３％Ｔｉ－３％Ｂ，Ａｌ－５％Ｔｉ－１％Ｂ中间合金对亚共晶Ａｌ－Ｓｉ合金的晶粒细化效果。结果表明，Ａｌ－３％Ｔｉ－３％Ｂ中间合金的细化作用明显优于Ａｌ－５％Ｔｉ－１％Ｂ。主要是Ａｌ－５％Ｔｉ－１％Ｂ中间合金加入熔体中，过量的Ｔｉ在ＴｉＢ２／熔体界面形成三元铝化物，通过包晶反应成为α－Ａｌ的异质晶核，但包晶反应温度的急剧下降是导致晶粒细化能力下降的直接原因；而Ａｌ－３％Ｔｉ－３％Ｂ中间合金加入熔体中，过量的Ｂ在ＴｉＢ２／熔体界面形成富Ｂ层，在冷却过程中，将发生共晶反应，生成大量的α－Ａｌ晶核，达到细化目的。