混合稀土对改善铝铜合金铸造性能的影响

通过研究混合稀土变质后铸造性能的变化，得出了Ａｌ－４．５％Ｃｕ合金流动性，线收缩率，热裂倾向，缩松及夹杂物等随稀土加入量的变化规律，知获得最佳综合铸造性能的最佳混合稀土加入量为０．２％，对混合土变质后的Ａｌ－４．５％Ｃｕ合金铸造性能的改善机制进行了分析，认为混合稀土之所以能改善合金的铸造性能，是因为改变了合金的凝固结晶特性，并使合金获得了净化。     

Al3Ti/ZL101原位复合材料的铸造性能研究

测试了Al3Ti/ZL101原位复合材料的流动性、线收缩率、热裂倾向及铸造应力，分析了影响铸造性能的各种因素。结果表明：Al3Ti/ZL101原位复合材料的热裂抗力较基体材料大、线收缩率较基体材料小、铸造应力略大于基体材料；在780℃以下，Al3Ti/ZL101原位复合材料的流动性优于基体材料。对Al3Ti/ZL101原位复合材料采用同基体材料相同的铸造工艺即能满足生产要求。     

Cu对Al-7Si-xCu-0.3Mg合金铸造性能的影响

采用单螺旋法和铸造性能多功能测试仪测定了铸造Al-7Si-xCu-0.3Mg(x=1.5%～3.5%,质量分数)合金的流动性、线收缩率和热裂倾向.结合Pandat相平衡软件计算相图、θ相(Al2Cu)的晶体结构特点和凝固显微组织的扫描电镜与能谱分析仪(SEM-EDX)分析,讨论了Cu含量对试验合金的流动性、线收缩率和热裂倾向的影响.随着Cu含量的同时,合金凝固时低熔点富Cu的共晶θ相(Al2Cu)明显增多,容易形成α(Al)枝晶骨架网,导致合金的流动性降低,线收缩率增加,热裂倾向增大.     

Al-20Cu合金的固液混合铸造

采用固液混合铸造工艺制备了Al-20Cu合金，并利用光学显微镜和扫描电镜等手段对合金的组织和性能进行了研究。结果表明，合金中的α—Al晶粒明显细化，α—Al晶粒尺寸控制在100μm以内，粗大的枝晶消除，晶粒呈球状形貌；合金的CuAl2—Al（Cu）共晶组织片间距减小；合金的力学性能显著提高。与普通铸造相比，抗拉强度由112MPa提高到205MPa，伸长率由0．5％提高到3．5％。     

钠变质及磷变质对ZL108合金铸造性能的影响

本文研究了钠变质和磷变质对ZL108合金铸造性能的影响。试验表明,磷变质比钠变质ZL108合金流动性好,收缩率高。所以,同一铸型及工艺的条件下,磷变质ZL108合金比钠变质ZL108合金更容易出现缩松缺陷。     

TiAl基合金涡轮熔模型壳离心精密铸造

对TiAl合金涡轮的立式离心熔模陶瓷型壳精密铸造进行了研究，合金熔配设备为水冷铜坩埚真空感应熔化炉。首先研究了TiAl合金铸造时的尺寸收缩问题，结果表明1600℃浇注时，合金的收缩率为1．32％，随着浇注温度的提高凝固收缩率显著提高。从合金熔体立式离心力场下充型模式方面考虑，涡轮浇注工艺应采用类似于重力充型的底注式较好。TiAl合金涡轮离心浇注内部组织致密、无气孔，存在的主要问题是欠浇缺陷，迎流面充型较弱。可以从提高离心转速和浇注温度两方面解决欠浇缺陷，但离心转速提高带来的安全隐患以及提高浇注温度带来的粘砂问题还需进一步研究。     

铸造Al—Li—Cu合金的组合与性能

本文对Al－Li－Cu三元系铸造合金的组织、性能与成分设计进行了研究。研究发现,Al－Li－Cu三元系铸造合金组织粗大,在枝晶间有大量的Cu偏析;粗大的组织严重损害合金的韧性,在时效态,Al－3Li－Cu三元合金的力学性能较高,但申长较低（0．4％）,采用双级时效时,伸长率可达1％。     

化学成分和浇注温度对7A04合金铸造性能的影响

采用水平直棒流动性金属型模具、临界长度法热裂模具、Tatur Test锥形模具分析研究了Mg、Zn、Cu、Ti合金元素和浇注温度对7A04合金铸造性能影响。结果表明：Mg含量提高后，合金流动指数降低、收缩率变大，Mg含量增加到1.01%时，热裂倾向增加，Mg含量继续增加到2.64%，热裂倾向变小；Zn含量提高后，流动性指数增加，收缩率变小，热烈倾向减小；Cu含量提高后，流动指数大幅提高，收缩率增加，热裂倾向减小；Ti含量提高后，流动指数和收缩率均有所提高，热烈倾向明显减小，当Ti含量由0.131%增加到0.20%时，铸造性能变化幅度减小。温度为720℃时，是热裂指数变化转折点。     

改善镍基合金铸造性能的研究

研究了稀土元素用于改善镍基合金铸造性能的可能性和效果。试验结果表明，在镍基合金中加入适量的稀土，可提高合金的流动性，降低其热裂倾向，对合金的线收缩率影响不大。     

高温铸造钛合金ZTA29工艺性能研究

ZTA29高温铸造钛合金以变形TA29合金为基础,本文研究该合金的工艺性能包括:流动性、填充性、焊接性、热裂性,铸造微观组织。结果表明,该铸造合金流动性仅为ZTC4合金的64%;合金填充性良好,可以实现1.5 mm壁厚铸件充型;ZTA29合金存在热裂性倾向,合金焊接性能一般,容易出现焊接裂纹,铸造组织为魏氏组织,α集束尺寸较大,热裂纹形成与硅化物偏析有关系。     

Effect of Ce on castability,mechanical properties and electric conductivity of commercial purity aluminum

Effects of Ce addition on microstructure,castability(fluidity and hot tearing sensitivity),mechanical properties and electric conductivity of commercial purity aluminum(CP-AI) were investigated through microstructure observation and performance tests.Results show that adding Ce in a CP-AI can considerably refine the grains,and has an important influence on the amount,crystallographic forms,and distribution of secondary phases.Addition of Ce also has a large impact on the fluidity and hot tearing sensitivity(HTS) of the CP-AI.With the addition of Ce from 0.1wt.%to 0.5wt.%,the fluidity of CP-AI is first increased remarkably and then decreased,and the HTS has an opposite response.The best castability of the studied alloys appears to be at 0.2wt.%-0.3wt.%Ce addition.The remarkable improvement in castability is attributed to the considerable refinement of grain structure.Ce addition can also lead to a significant rise in electric conductivity.The maximum conductivity of the as-cast CP-AI is 59.7%IACS with an addition of 0.2wt.%Ce.The T7 heat treatment can further improves the conductivity to 60.7%IACS.The Ce-induced evolution of the secondary phases is believed to be the mechanism for it.     

A solidification model for prediction of castability in the precipitation-strengthened nickel-based superalloys

The Scheil equation was used to model the solidification path, microsegregation of alloying elements in the interdendritic regions, solidification temperature ranges, and to predict the formation of secondary structures and the castability behavior of as-cast superalloys. 4 experimental alloys with pre-specified γ-Ti,Nb,Al,Mo composition containing different Nb, Ti and Al contents were designed using vacuum induction melting furnace. The produced as-cast superalloys were characterized using optical and scanning electron microscopy equipped with energy dispersive X-ray spectrometer and TG–DSC analysis. The experiments showed logic conformity to the modeling results. The model and experiment confirmed the highest segregation behavior for Ti and Nb. All the experimental superalloys indicated the remarkable tendency to form secondary eutectic structures at the last stages of solidification. Superalloy with chemical composition of γ-3.5%Mo,1.8%Al,4%Ti,2.9%Nb showed the shorter solidification temperature range and the best castability.     

Comparison of castability,mechanical, and corrosion properties of Mg-Zn-Y-Zr alloys containing LPSO and W phases

The Mg-Zn-Y-Zr alloys with long-period stacking-ordered (LPSO) and W eutectic phases were investigated to develop new magnesium casting alloys. The temperatures for T6 heat treatment were selected based on the hardness and electrical conductivity measurements. The hot tearing susceptibility of the alloys with LPSO phase is lower than that of the alloys with W phase, which is associated with the freezing range of the alloys. However, the investigated alloys displayed the same fluidity. Under T6 conditions, increasing the Y content in the alloys resulted in increased yield strength, whereas other tensile properties were similar for the alloys. The corrosion resistance was higher for the alloys with LPSO phase compared to that of the alloys with W phase. Mg-2.5Zn-3.7Y-0.3Zr (mass fraction, %) alloy with LPSO phase possessed high castability and mechanical properties, with a corrosion rate of 2 mm/year.     

Pseudo-elastic deformation behavior in a Ti/Mo-based alloy

It is shown that the pseudo-elastic response in a series of Ti–Mo–V–Nb–Al alloys with 8–11 wt.% Mo is highly sensitive to both composition and heat treatment. Recovery of up to 3.0% strain has been observed but it appears that this may not be due to reversible formation of α^″ martensite.     

Rendering wrought aluminium alloys castable by means of minimum composition adjustments

Wrought alloys have low fluidity and are prone to hot tearing, which make them difficult to cast. The presence of eutectic-forming elements in the alloy composition lessens these effects. For this reason, the constituents of casting alloys tend to include a eutectic portion. Typically, silicon is added to aluminium alloys to provide casting ability by forming the aluminium–silicon eutectic. However, the presence of silicon in aluminium alloys is associated with a number of issues that do not allow these alloys to reach their full potential. In this publication we report results of our investigation of three alternative eutectics: Al–6.1Ni, Al–1.8Fe, and Al–1.75Fe–1.25Ni. Our results indicate that these eutectics have satisfactory fluidity and resistance to hot tearing and higher strength than the aluminium–silicon eutectic. We also found that introducing these eutectic compositions into 7075 wrought alloy results in a castable composition with yield strength comparable to that of the wrought alloy.     

Grain refinement effects of Al based alloys with low titanium content produced by electrolysis

A series of Al based alloys with low titanium contents (mass fraction) from 0.178% to 0.526% were directly produced in ordinary industrial electrolyzer,The electrolyzing results show that producing Al based alloys analysis shows that this method has a great refining effect on transiting the coarse columnar grains in pure Al to equiaxed grains.The grain sizes decrease with the increase of titanium content and tend to a low limit at about 130μm .During the solidification,the non-equilibrium distribution of titanium leads to a great growth-restricting effect and a constitutional under-cooling zone in front of the growing liquid /solid interface.     

Fe3Al合金的流动性及热力学分析

Fe3Al合金是优秀的耐热工程材料,在测定合金流动性工艺参数的基础上,用热力学观点分析了主要添加元素Al对合金流动性的影响规律。根据合金凝固动态曲线的测定结果,Al含量的增加,使凝固区域增宽,由于发达的枝晶阻碍了合金的流动,使流动性下降。合金的液相线温度随Al量的增加而降低,Al含量从24%增至35%时,其过热度约增加1倍。过热度的提高,将有利于合金的流动性提高。研究认为:Al对合金过热带来的有利作用远不及合金结晶温度范围增宽以及高熔点Al2O3数量增多而造成的不利影响。因此,Al含量的增加将导致合金的流动性降低。测试结果表明:Cr元素由于提高合金的液相线温度,使合金的流动性下降。Mo和Zr元素有利于合金流动性的提高。     

Al含量对铸态V-Alx合金组织和力学性能的影响

V-Al合金膜有着良好的抗氢脆性和高的氢渗透率,有望成为未来取代Pd合金膜的替代材料。V-Al合金的显微组织不仅影响氢分离性能,还将影响强度和塑性成形性能。本研究通过真空非自耗电弧炉熔炼制备了氢分离用V-Alx(x=5,10,20,30,at%,下同)合金。利用扫描电镜/能谱仪、X射线衍射仪及拉伸试验机和维氏硬度仪等手段,研究了Al含量对铸态V-Alx合金微观组织和力学性能的影响。结果表明:V-Alx合金凝固组织均由V基固溶体及Al2O3粒子组成。Al元素的添加对合金有细化晶粒的作用,随Al含量增加,合金晶粒尺寸减小。当Al元素含量为5at%时,合金抗拉强度达到最大,为236MPa,比纯V提高了12%,这是细晶强化、固溶强化和析出强化的共同结果,此时延伸率相比纯V略有降低。当Al元素含量达到10at%及以上时,Al2O3粒子发生粗化导致合金抗拉强度下降,延伸率急剧下降,合金失去塑性。     

Martensitic transition and shape memory effect of Ti-Zr-Mo series alloys

Development of shape memory alloys is always one of the most important directions for functional Ti alloys. The Ti-Zr-Mo series alloys with various Mo contents were prepared. The main aim of the current work is to investigate the effects of Mo on martensitic transition and shape memory effect of Ti-Zr alloy. The X-ray diffraction and transmission electron microscope results indicate that the phase constitution of the examined alloys is greatly dependent on Mo content. The Ti-Zr-Mo alloy with 2 wt% Mo is composed mainly of α′ martensite and a few β phase. As the Mo content increased to 4 wt%, the Ti-50Zr-4Mo alloy consists of α″ martensite and β phase. As the Mo content further increased to 8 wt%, the alloy consists mainly β phase and a barely detectable amount of α″ martensite. Thermal analysis shows that the reverse martensitic transition temperature of the examined alloys decreases with the increasing of Mo. The reverse martensitic transition start, A_s, temperature is approximately 584 °C for Ti-50Zr-2Mo alloy and 519 °C for Ti-50Zr-4Mo, respectively. And the martensitic transition start, M_s, temperature is approximately 553 °C and 501 °C for that two alloys, respectively. But no obvious exothermic and/or endothermic peak can be observed in DSC curve of Ti-50Zr-8Mo alloy. Furthermore, the effect of Mo content on shape memory recovery ratio, η, of the examined alloys was also investigated. Results show that the η first increases and then decreases with the increasing of Mo. The alloy with 4 wt% Mo has the maximum η approximately 13.8%. The influencing mechanism of Mo content on shape memory effect of the examined alloys was also discussed. This findings not only supplied a series of shape memory TiZr-based alloys, but also enriched and deepened the theory of shape memory effect.     

A new,third-generation,single-crystal,casting superalloy

The CMSX®-10 alloy is a third-generation, single-crystal (SX), nickel-based casting alloy that is characterized by its 6 wt.% rhenium content, relatively high refractory element level (W+Ta + Re+Mo), and low level of chromium employment. Based on published data, the alloy's high-temperature creep-rupture resistance is greater than all other nickel-based alloys (approximately 30 °C better than CMSX-4 and PWA1484). Moreover, the alloy's composition is balanced to provide an attractive blend of SX component castability, heat treatability, impact strength, fatigue strength, and resistance to environmental degradation. Most notably, the alloy provides extremely good bare hot corrosion resistance, despite its novel and relatively low (2–3 wt.%) chromium content.