Effect of rare earth alloy modification on high carbon equivalent gray cast iron of automotive brake drum

Effect of rare earth alloy modification on properties and microstructure of high carbon equivalent gray cast iron was investigated.The experimental results show that in the way of mechanical property,when the addition of rare earth alloy is 0.2% and 0.3%,the tensile strength of cast iron increases.In the way of microstructure,the addition of rare earth alloy increases the number of primary austenite dendrites,reduces secondary dendritic arm spacing,and changes the eutectic size and quantity.When rare earth alloy is added into gray cast iron,the morphology and quantity of graphite play a major role on the improvement of tensile strength.     

Effects of Rare Earth Pr/Ce on Tribological Behavior of ADC12 Alloy

The microstructure and microhardness of ADC12 alloy that was mixed with 0,0.3,0.6,and 0.9 wt.% rare earth praseodymium/cerium (Pr/Ce) were studied.The addition of Pr/Ce improved the microhardness of the alloys.The ADC12+0.6 wt% Pr/Ce alloy displayed the smallest grain size and maximal microhardness.The tribological behavior of the alloys was tested by the pin-on-disc dry sliding friction pair with a sliding velocity of 0.21 m/s under various loads (20,40,60,80 N).The wear morphology was observed by a scanning electron microscope (SEM) and the wear mechanism was discussed.The result indicated that the wear resistance of ADC12+0.6 wt% Pr/Ce alloy was the most optimal.The wear rate relative to the matrix is reduced by 67.5% under a load of 20 N.The wear mechanism is adhesive wear.     

Influence of rare earth (Ce and La) addition on the performance of Al-3.0 wt%Mg alloy

The influences of rare earth elements (cerium and lanthanum) on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.     

稀土Er对Al-Si-Cu钎料显微组织与性能的影响

为了研究微量稀土元素Er对Al-7Si-20Cu钎料合金性能的影响,进行了不同wEr对Al-7Si-20Cu合金熔化温度、润湿性能及力学性能的试验研究.结果表明,添加微量Er对Al-Si-Cu钎料合金的熔化温度无显著影响,但显著提高Al-Si-Cu钎料合金对被焊基体铝合金(LF21)的润湿能力,尤其是当wEr为0.05%~0.1%时最为显著.显微组织分析表明,随着wEr的增加,钎料显微组织细化,特别是针状共晶Si的长度逐渐减小.     

Mg-Al合金非平衡凝固共晶组织及形成机理

为了研究Mg-Al合金非平衡凝固组织,利用扫描电镜(SEM)、x-射线衍射仪以及拉伸性能测试,分析了金属型铸造Mg-x%Al(x=8、10、12)合金的铸态组织.结果表明,Mg-x%Al(x=8、10、12)合金的铸态组织由α固溶体、沿晶界分布共晶组织及其附近的次生相所组成,共晶组织以β-Mg₁₇Al₁₂为基且其上分布着粒状α相,次生β相与α固溶体以片层相间的形式出现.采用金属型铸造,实验合金的冷却速度较快,先形成离异共晶的β-Mg₁₇Al₁₂相,后形成以β-Mg₁₇Al₁₂为基的共晶组织.该组织为类似于铁碳合金中莱氏体的非规则共晶体,强度和塑性很低,因此,Mg-x%Al(x=8、10、12)合金的力学性能普遍较低.     

稀土元素对工业纯铝机械性能的影响

通过稀土元素铈、镧和混合稀土对工业纯铝组织的改善，研究了它们对工业纯铝机械性能的影响，并利用金属学原理和凝固理论对其机理进行了分析．结果表明，加入质量分数为0．2％～0．3％的稀土元素La或0．4％的Ce，可以提高工业纯铝的拉伸性能；加入质量分数为0．2％-0．3％的稀土元素La或0．1％～0．3％的Ce，可以提高工业纯铝的延伸率；而混合稀土对工业纯铝的拉伸性能没有明显的影响．     

Ce在铝硅合金中的显微分布研究

用涂敷法自射线照相法研究了Ce在铝硅合金中的分布。结果表明,Ce在初生α-Al和多数初生Si中是贫化的,Ce主要富集于共晶体中。共晶Si中的含Ce量远多于共晶α-Al中的含Ce量。     

Refinement role of electromagnetic stirring and calcium in AZ91 magnesium alloy

Effects of calcium addition and electromagnetic stirring on the microstructure of AZ91 magnesium alloy and refinement mechanism were investigated. The results show that calcium addition ranging from 0.1wt% to 0.3 wt% does not lead to formation of any new phases but cause the refinement of ascast microstructure.However, combined calcium alloying and electromagnetic stirring significantly decrease the grain size, change the morphologies of the β-Mg17Al12 phases,and reduce their volume percentage. The minimum grain size of AZ91 alloy is obtained in the case of the addition of 0.2 wt%Ca with exciting voltage of 100 V. The microstructural refinement is attributed to the increase of the degree of undercooling and nucleation temperature of primary α-Mg phases on the basis of DTA analysis results.     

变质Al-xMg2Si合金中超细初生Mg2Si的制备

在未变质Al-xMg₂Si合金中,随着Mg\Si含量从18降低到14 wt.%,初生Mg₂Si晶粒尺寸发生明显细化,由~30 mm减小到~10 mm;当合金中Mg\Si的含量降低到12 wt.%,初生Mg₂Si全消失,其金相组织为单一共晶相组成。对Al-xMg₂Si进行0.5 wt.% Ca-Sb复合变质处理,当合金中Mg\Si的含量降低到10 wt.%,合金中金相组织为初生α-Al+共晶Mg₂Si组成。在0.5 wt.% Ca-Sb复合变质的Al-xMg₂Si合金中,由于变质剂的作用,在Al-xMg₂Si合金中,树枝晶状初生Mg₂Si消失,转变为细小的多边形,随着合金中Mg\Si含量从18降低到12 wt.%,初生Mg₂Si晶粒尺寸从~15 mm降低到~5 mm,形成超细初生Mg2Si晶体。对合金进行力学性能测试发现,超细初生Mg2Si的形成对提高合金强度、硬度作用较大。     

钕对AZ91镁合金组织及机械性能的影响

采用微观分析、机械性能测试及断口分析等方法研究了钕对AZ91-Nd镁合金(w(Nd)=0,0.1%,0.3%,0.5%,1.0%,1.5%)的微观组织和机械性能的影响。结果表明:Nd以固溶和金属间化合物(A l11Nd3)的形式存在时具有细化晶粒、抑制二次β相析出、使不完全离异共晶转化为离异共晶的作用;Nd通过固溶强化、析出强化和细晶强化增加了合金强度和硬度,并改善了塑性;加入Nd后合金的断裂机制从脆性解理断裂转变为准解理断裂。     

稀土对纤维相Cu-12%Ag合金组织性能的影响

为研究稀土微合金化在纳米纤维强化Cu-Ag合金中的作用，制备了纤维相增强Cu-12%Ag和Cu-12%Ag-0.3%RE合金．采用冷拉拔结合中间热处理方法制备该类合金，观察并测定了不同变形程度下稀土元素对合金显微组织、力学性能和电学性能.实验结果表明，随变形程度增大，合金硬度和强度上升，相对电导率下降.稀土元素可增加原始组织枝晶轴间距、共晶体数量及共晶体中Ag的质量分数，提高合金的硬度，但对合金抗拉强度没有明显影响.在较低的变形程度范围内，稀土元素使合金导电性能略有降低.在大变形范围内，稀土元素可在一定程度上改善导电性能.     

Influence of rare earth modification and homogenization on the microstructure and mechanical properties of recycled can 3004 aluminum

The microscopic structure of waste can aluminum material was researched by adding Al5TiB refining agent, La-Ce rare earth and mixed rare earth modifiers, and the microstructure and mechanical performance of the modified aluminum material were studied. The experimental results show that the optimal refiner addition amount is 1.1wt%; the material performance can be significantly improved when the content of La-Ce rare earth ranges to a certain degree, but the mixed rare earth barely affects the refinement effect of the aluminum. When being homogenized, the mixed rare earth plays more obvious role in refining the aluminum material than La-Ce rare earth. The optimal plan is modifying the aluminum material with 3wt% mixed rare earth and homogenizing with annealing temperature of 580 ℃, annealing time of 12 hours and heating rate of 5 ℃/min while refining the material with 1.1wt% Al-5Ti-1B.     

稀土高强高导耐热抗拉铝合金电缆的研究

研究了将La加入Al-Mg-Si合金;将Y和Ce加入Al-21-Mg合金.获得Al-Mg-Si-La高强高导电缆合金和Al-Zr-Mg-Y-Ce耐热高导电缆合金.通过检测和组织观察,从而提高了电缆合金的强度.耐热性和导电性.另外稀土改善了铝合金的加工性能.减少了冷拉缺陷.     

镁合金晶粒细化剂研发现状及展望

阐述了目前镁合金液态下几种晶粒细化剂如含碳细化剂、硼化系合金细化剂、稀土元素或混合稀土晶粒细化剂、含Zr元素合金以及其它合金元素如Ca、Sr、Ti等晶粒细化剂的研究现状及最新进展,并对液态下镁合金晶粒细化机理进行分析,针对性提出镁合金细化剂研制的几种思路,对今后的研制方向进行了展望.     

热等静压处理对NiAl-Mo（Nb）合金显微组织和力学行为的影响

研究了热等静压处理对NiAl-Mo（Nb）合金显微组织和力学行为的影响。结果表明：铸态NiAl-Mo（Nb）合金由NiAl和Mo相组成共晶胞状组织,胞界处尺寸较大的白色相为含有Nb元素的富Mo相。热等静压处理后,胞状形貌变得不明显,Mo相变得细小、均匀,且Mo相发生了球化。热等静压处理明显提高了铸造合金的屈服强度,在低温及高应变速率时,强度提高80%左右;而在高温及低应变速率时,强度提高30%左右。     

Sr对Mg-3Al-1Zn镁合金铸态组织的影响

研究了Sr对Mg-3Al-1Zn镁合金铸态组织的影响．结果表明：在Mg-3Al-1Zn合金中加入0．01％和0．05％的Sr对合金组织中合金相种类没有影响，但Sr含量为0．1％时有Al4Sr相存在．同时，加入微量Sr使合金组织中Mg17Al12相的数量减少、分布更加弥散和均匀，其中Sr含量为0．1％时合金组织中的Mg17Al12相基本上呈断续状分布．此外，研究结果还发现微量Sr对Mg-3Al-1Zn合金的组织有明显的细化作用．     

Sr对Mg-3Al-1Zn镁合金铸态组织的影响

研究了Sr对Mg-3Al-1Zn镁合金铸态组织的影响.结果表明:在Mg-3Al-1Zn合金中加入0.01%和0.05%的Sr对合金组织中合金相种类没有影响,但Sr含量为0.1%时有Al4Sr相存在.同时,加入微量Sr使合金组织中Mg17Al12相的数量减少、分布更加弥散和均匀,其中Sr含量为0.1%时合金组织中的Mg17Al12相基本上呈断续状分布.此外,研究结果还发现微量Sr对Mg-3Al-1Zn合金的组织有明显的细化作用.     

Ce对Al-Zn-Mg-Cu-Sc合金组织和力学性能的影响

为了研究Ce元素对T6态Al-7.5Zn-2Mg-2.3Cu-0.1Sc合金显微组织和力学性能的影响,通过改变合金中Ce元素的添加量,采用光学显微镜、扫描电子显微镜和电子万能实验机对合金的显微组织、拉伸断口形貌和力学性能进行了研究.结果表明,加入质量分数为0.2%的Ce元素可以显著细化Al-7.5Zn-2Mg-2.3Cu-0.1Sc合金的铸态和T6态显微组织.在合金的T6处理过程中随着时效时间的增加,合金硬度和抗拉强度均先增加后降低,合金的硬度和抗拉强度峰值分别为216 HB和681.7 MPa,合金最高屈服强度为638.2 MPa.合金拉伸断口呈韧脆混合断裂特征.     

Microstructure Evolution of Semi-solid Processed Hyper-eutectic Al-30%Si Alloy

Semi-solidmetalformingtechnologyhasachievedgreatprogressinthepasttenyearsbecauseitoffersmanypotentialadvamagessuchasformingnet-shapeparts,decreaseofmicrosegregation,reductionofporosity[1--3].Thistechnologyhasbeenappliedinproductionofsomehypo-eutectic...     

稀土元素镧和锶对镍基钎焊料焊接性能的影响

碳化钨(WC)复合涂层是一种高温下使用的有效耐磨蚀保护涂层.在BNi-2钎料粉末中添加稀土粉末,用机械合金化技术制备了改进的BNi-2钎料粉末,并在Q235钢基体上制备了碳化钨复合涂层;采用SEM观察了涂层显微组织,分析了稀土元素La和Ce对钎料焊接性能的影响规律.结果表明,在BNi-2合金中分别加入0.1 Wt.%稀土元素La,0.05 Wt.%稀土元素Ce,并采用机械合金化制备的粉状镍基焊料,与母材润湿性良好,焊接性能有所提高.采用此焊料及渗透钎焊技术可以制备出界面结合良好的WC复合涂层.