Effects of Al-Ti-B-RE grain refiner on microstructure and mechanical properties of Al-7.0Si-0.55Mg alloy

To investigate the effects of Al-Ti-B-RE grain refiner on microstructure and mechanical properties of Al-7.0Si-0.55Mg （A357） alloy, some novel Al-7.0Si-0.55Mg alloys added with different amount of Al-STi-1B-RE grain refiner with different RE composition were prepared by vacuum-melting. The microstructure and fracture behavior of the AI-7.0Si-0.55Mg alloys with the grain refiners were observed by X-ray diffraction （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM）, and the mechanical properties of the alloys were tested in mechanical testing machine at room temperature. The observation of AI-Ti-B-RE morphology and internal structure of the particles reveals that it exhibits a TiAl3/Ti2Al20RE core-shell structure via heterogeneous TiB2 nuclei. The tensile strength of Al-7.0Si-0.55Mg alloys with Al-5Ti-1B-3.0RE grain refiner reaches the peak value at the same addition （0.2%） of grain refiner.

Microstructure Refinement of Al-5Ti-B Grain Refiner with Electromagnetic Energy

The influence of the electromagnetic energy on the microstructure of Al-5Ti-B grain reflner was discussed.In this study,the electromagnetic energy was applied above the liquid phase line temperature.Compared with Al-5Ti-B without electromagnetic energy applied,the experimental results show that the size of secondary particles is reduced and its size distribution becomes more uniform.Simultaneously,the secondary phase particles are uniformly spread in the matrix response to the electromagnetic energy.Moreover,when adding Al-5Ti-B with electromagnetic energy to the pure aluminum melt,it is clear that the electromagnetic energy has a signiflcantly impact on reflning properties of Al-5Ti-B.The mean size of pure aluminum is reduced by 27.6%in maximum with more uniform size distribution.The change in the microstructure is attributed to the electromagnetic energy changes the melt structure.With the electromagnetic energy entry into the system,the electromagnetic energy reduces the size of atomic clusters and increases the number of atomic clusters,thus the number of nuclei increases.

稀土Y及Al-5Ti-B细化剂复合添加对A356铝合金组织和力学性能的影响

用Al-20Y变质剂和Al-5Ti-B细化剂处理A356铝合金熔体,研究稀土Y与Al-5Ti-B复合添加对A356铝合金组织和力学性能的影响。结果表明:稀土Y和Al-5Ti-B复合添加能提高形核率、细化α-Al晶粒尺寸和改变共晶硅形貌,共晶硅的形貌由针状和板片状变为短杆状和颗粒状,使铸造铝合金的力学性能提高。添加稀土Y和Al-5Ti-B的A356铸造铝合金的抗拉强度、屈服强度和延伸率分别为146 MPa、98 MPa和4.0%。

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 Mn and Sn on microstructure of Al-7Si-Mg alloy modified by Sr and Al-5Ti-B

The effects of Mn and Sn on the microstructure of Al?7Si?Mg alloy modified by Sr and Al?5Ti?B were studied. The results show that the columnar dendrites structure is observed with high content of Sr, indicating a poisoning effect of the Al?5Ti?B grain refinement. In addition, Sr intermetallic compounds distribute on the TiB2 particles, which agglomerate inside the eutectic Si. The mechanism responsible for such poisoning was discussed. The addition of Mn changes the morphology of iron intermetallic compounds fromβ-Al5FeSi toα-Al(Mn,Fe)Si. Increasing the amount of Mn changes the morphology ofα-Al(Mn,Fe)Si from branched shape to rod-like shape with branched distribution, and finally convertsα-Al(Mn,Fe)Si to Chinese script shape. The microstructure observed by transmission electron microscopy (TEM) shows that Mg is more likely to interact with Sn in contrast with Si under the effect of Sn. Mg2Sn compound preferentially precipitates between the Si/Si interfaces and Al/Si interfaces.

Al-5Ti-B及RE对挤压铸造7075铝合金传动空心轴组织和性能的影响

本文采用挤压铸造的方法制备了7075铝合金传动空心轴,研究了Al-5Ti-B及RE对挤压铸造7075铝合金铸件微观组织和力学性能的影响.结果表明:未加入细化剂的合金晶粒大小约为50μm,拉伸强度为454 MPa;加入0.29%RE的合金和1%A1-5Ti-B的合金,晶粒尺寸分别了减小到26μm和25μm,拉伸强度分别提高了16.3%和22.2%;同时加入0.29%RE和1%A1-5Ti-B对合金组织细化最为明显,晶粒尺寸减小到18μm,拉伸强度提高了26.6%,达到575MPa,延伸率为8.16%,布氏硬度为184.

Al-5Ti-B和稀土Y复合添加对A356合金半固态凝固组织的影响

采用稀土Y及Al-5Ti-B中间合金对A356铝合金进行细化处理,并用低温浇注技术制备半固态坯料。研究了单独添加Al-5Ti-B和稀土Y以及两者复合添加时对A356铝合金半固态凝固组织的影响。研究结果表明,Al-5Ti-B和稀土Y对A356铝合金半固态初生相的形貌及尺寸均有不同程度的改善。将两者复合添加时,可显著提高合金中初生相的形貌及尺寸,得到细小、圆整且分布均匀的半固态组织,其添加量的最佳组合为0.02%的Ti与0.5%的Y。探讨了两者复合添加对合金凝固组织的细化机理。

Al-5Ti-B细化剂对A356合金微观组织的影响

制定合理的熔炼工艺熔配A356合金,并在浇注前加入不同含量的Al-5Ti-B细化剂对合金液进行细化处理,研究细化剂对A356合金组织和性能的影响.研究结果表明:加入Al-5Ti-B能使A356合金中的初生α-Al相显著细化,该相由粗大的树枝晶变为细小、无定向的枝晶;由于晶粒变小晶界增多,硅相变得更为分散地分布在枝晶和晶粒间隙内,导致粗大的针片状共晶硅减少且长度变短,使应力集中程度降低.当细化剂加入量在1.0%时细化效果最好,二次枝晶间距为22.98μm,铸态下其硬度为62.4HB,而不经过细化处理的A356合金,其硬度仅为52.0HB,相比提高了12.4%.

Effect of trace boron on grain refinement of commercially pure aluminum by Al-5Ti-1B

The effect of boron content on grain refinement of commercially pure aluminum by Al-5Ti-1B was quantitatively assessed.When the boron content is less than 0.03 wt.%,the refining performance of Al-5Ti-1B gradually is weakened as the boron content increases,which is attributed to the reaction of boron with the Al_(3)Ti interlayer on TiB_(2)and the consumption of solute Ti.On the contrary,when the boron content exceeds 0.03 wt.%,the refining performance of Al-5Ti-1B gradually recovers with increasing boron content,which is related to the formation of primary AlB_(2)particles that provide additional nucleant substrates.

细化剂Al-5Ti-B添加量对铝合金晶粒度的影响

利用本企业相关设备开展试验,研究了钛元素添加量对铝合金晶粒组织的影响,研究了在铝合金熔铸过程中钛元素的最优添加量,使用最少的Al-5Ti-B丝最经济、合理的使铝合金晶粒组织达到要求。研究结果表明:当铝合金熔体中钛含量添加量为0.01%,同时增加机械搅拌可以使铝合金晶粒组织达到控制要求。

Grain refining action of Ti existing in electrolytic low-titanium aluminum with Al-4B addition for superheated Al melt

The effects of superheating temperature on the grain refining efficiency of Ti existing in electrolytic low-titanium aluminum(ELTA)without and with the Al-4B addition and the Al-5Ti-1B master alloy in pure Al were comparatively investigated. The results show that the Ti existing in ELTA without Al-4B addition exhibits a certain grain refining efficiency when the melt superheating temperature is lower,but the efficiency decreases rapidly when the superheating temperature is higher.The grain refining efficiency of the Al-5Ti-1B master alloy is better than that of the Ti existing in ELTA without Al-4B addition at any superheating temperature,but it also decreases obviously with the increase of the superheating temperature.One important reason is that the TiB2 particles coming from the Al-5Ti-1B master alloy can settle down at the bottom of the Al melt easily when the superheating temperature is increased,thus decrease the number of the potent heterogeneous nuclei retained in the Al melt.If the Al-4B master alloy is added to the ELTA melt,the grain refining efficiency of the Ti existing in ELTA can be improved significantly, and does not decrease with the increase of the superheating temperature.This perhaps provides us a possible method to suppress the effect of the superheated melt on the microstructures of aluminum..

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.

脉冲电流对7075铝合金铸态组织的影响

研究了脉冲电流及Al-5Ti-B变质剂对7075铝合金铸态组织的改善和机理。结果表明,通入电脉冲及添加变质剂能抑制二次枝晶的生长,改善铸造组织的形貌,基体主要是均匀的等轴晶和近球形晶粒,同时,与直接浇铸的试样对比,合金中铜和铁元素的偏析现象得到一定程度缓解。

Al-5Ti-B细化剂对ZA4-1合金微观组织和力学性能的影响

用离心铸造方法制备ZA4—1合金铸件，借助扫描电镜、金相显微镜和万能试验机研究A1-5Ti—B细化剂含量对ZA4-1合金微观组织和力学性能的影响。结果表明：ZA4-1合金中加入含量为0．01%-0．04％的A1-5Ti—B细化剂能够有效细化晶粒，随着细化剂含量增加，细化效果下降。本实验中获得A1-5Ti—B细化剂最佳含量为0．02％。当A1-5Ti-B细化剂含量为0．02％时，合金组织出现等轴晶粒，延伸率提高至3％，但抗拉强度降低了28％，在拉伸实验过程中，试件几乎没有出现颈缩现象，而是直接发生脆性解理断裂。相比未加入细化剂的合金，解理面变小，解理台阶增多，出现较多的撕裂岭和裂纹，还出现了部分小的韧窝，提高了合金的塑韧性；当AI-5Ti—B细化剂含量增加到0．04％时，晶粒的大小又有增大的趋势，合金晶粒细化效果降低，抗拉强度有小幅增加，金相显微镜观察到晶界处有较多的共晶组织析出，共晶组织的出现降低了ZA4-1合金的强度，并且出现脆性相富集于晶界处，形成缺陷，使合金的塑性降低。

Al-5Ti-B合金等径角挤压变形过程的数值模拟

运用有限元模拟等径角挤压过程(ECAP),分析了试样的变形条件与模具的受力状态和金属的流动规律。材料的变形主要集中在模具两个通道的拐角处,变形梯度较大。在ECAP过程中不可避免产生末端效应,因此试样应该足够长,以便能够产生一个稳定变形区,从而获得良好的挤压效果。挤压速度对等径角挤压的影响不大,考虑到挤压效率的影响,应采用较高的挤压速度。

快凝处理Al-5Ti-B合金的组织变化及其细化效果

采用电弧熔炼吸铸法和单辊旋淬法分别对工业用Al-5Ti-B合金进行了重熔快凝处理。对快凝处理Al-5Ti-B合金的组织变化及其对纯铝的细化效果和抗衰退能力进行了研究。结果表明,电弧熔炼吸铸法和单辊旋淬法处理可使Al-5Ti-B合金的组织中原有粗大板条状TiAl3相转化为细小且均匀分布的针状或颗粒状,并可消除TiB2粒子的聚集,使其分布更均匀;快凝处理可明显改善Al-5Ti-B合金的晶粒细化效果,减少其使用量;在铝熔体长时间保温时,快凝处理Al-5Ti-B合金的细化效果不会明显衰退。

The Combined Effects of Electromagnetic Stirring and Al-5C Master Alloy on Grain Refinement of AZ31 Magnesium Alloy

Al-5wt.%C(similarly hereinafter)master alloy as a refiner has been developed by powder in situ synthesis process,and the combined effects of Al-5C refiner and EMS(electromagnetic stirring)on grain refinement of AZ31 alloy are investigated.The results indicate that the A1-5C refiner and EMS can remarkably reduce the grain size of AZ31 alloy. The average grain size of AZ31 alloy decreased firstly and then increased with the increasing addition amount of the Al-5C master alloy,and the optimum addition amounts is 2wt.%.While the AZ31 alloy with 3wt.%Al-5C master alloy solidified under EMS,the average grain size further reduced and is less than that treated only by EMS.The refining mechanism of AZ31 alloy refined by Al-5C master is owing to the polygonal Al_8(Mn,Fe)_5 particles acting as nucleating substrates for α-Mg grain.The more distribution of Al_8(Mn,Fe)_5 and Al4C3 particles generated by EMS contribute to the further refinement when treated by combining with Al-5C refiner.

熔体处理和双向电磁搅拌复合快速制浆技术

分析了中间合金微细粉末熔体处理工艺和双向电磁搅拌工艺中，Al-5Ti-B合金粉末粒度、粉末加入量、加入温度、静置时间、中间合金加入顺序、单向旋转时间、电源频率、浇注温度和搅拌时间等工艺参数对A356合金半固态浆料的组织和制备效率的影响规律及其原因，开发出适合于铝合金的熔体处理＋双向电磁搅拌半固态浆料复合制备技术。结果表明：该技术可在20-25s内制备出α（Al）的形状因子约为0．85、晶粒尺寸为70-80μm（空冷尺寸）的A356合金半固态浆料。

IMPROVEMENT IN TENSILE PROPERTIES OF α+β TYPE Ti ALLOYS BY HYDROGEN TREATMENT

A new process to refine the microstructure of α+βtvpe Ti alloys was developed by using hydrogen as a temporary alloying element.It involves hydrogenating the alloys below the hydrogenated β transus temperature about 0-40 K,air cooling to room temperature and then dehydrogenating at 948 K.Ti-6AI-4V and Ti-5AI-2.5Fe alloys treated hy this new process show much refined microstructures,and the yield strength,ultimate strength as well as the elongation increase 8—15,5—13 and 7—14% respectively

相机壳体用含RE、Sr和AlTiB压铸镁合金工艺优选及组织性能

采用光学显微镜(OM)、X射线衍射分析(XRD)、带有能谱仪(EDS)的扫描电子显微镜(SEM)、透射电子显微镜(TEM)和力学性能测试等方法,研究了压射速度和压射比压对RE(Ce和Y)、Sr和AlTiB复合变质的AZ91D压铸镁合金相机壳体毛坯件的微观组织和力学性能的影响。结果表明:随着压射速度和压射比压的增加,合金的强度先增大后减小、伸长率先减小后增加,由此得到优化的压铸工艺参数为浇铸温度680℃、压射速度6 m/s和压射比压90 MPa。RE、Sr和AlTiB复合变质显著细化AZ91D合金的α-Mg晶粒和Mg_(17)Al_(12)相,同时在基体中引入了细小弥散的TiB_(2)、Al_(11)Ce_(3)、Al_(2)Y和Al_(10)Ce_(2)Mn_(7)相,它们的协同强化作用显著提升了合金的强度。因此,变质的合金获得了最优的力学性能:抗拉强度为287 MPa,屈服强度为196 MPa,伸长率为4.7%。