Effects of Sb,Sr, and Bi on the material properties of cast Al-Si-Cu alloys produced through heated mold continuous casting

Rare earth metals can create a fine eutectic Si structure in cast Al-Si_10.6-Cu_2.5 (ADC12) alloys produced through heated mold continuous casting. Fine and spherical eutectic Si phases are created in the ADC12 alloys through the addition of Sr0.04, and fine lamellar eutectic Si phases are created through Sb and Bi addition. Crystal orientation on the face perpendicular to the casting direction is formed by [110]; however, this uniform formation is collapsed in the ADC12 alloy with an increasing amount of Sr addition, such as Sr > 0.04%. The shape of the eutectic Si is statically analyzed, and the effects of the eutectic Si characteristics on the mechanical properties are examined experimentally. On the one hand, the mechanical properties of the ADC12-Sr alloy increase with increasing Sr content because of the fine eutectic Si, the randomly orientated crystal formation, and so on. On the other hand, the material ductility increases in the ADC12 alloy with increasing addition of Sb and Bi elements. A high fracture strain of approximately 14% is obtained for the ADC12-Bi1.5 alloy.     

Mg-6Al-3Zn-2Ca-xNd合金微观组织及性能研究

研究了添加不同含量的稀土元素Nd对AZC632镁合金显微组织和力学性能的影响,结果表明,在AZC632镁合金中添加适量的Nd元素,能使合金基体组织均匀、晶粒细化,第2相β-Mg17Al12分离变细变少,由连续网状分布转变为离散断续的条状及点状分布,同时也出现了针状的新相。随着Nd元素含量的增加,AZC632镁合金的抗拉强度、伸长率及硬度也都得到了明显的改变。     

PdPtAu alloys for low-temperature precision resistors

Palladium-rich PdPt and PdAu alloys exhibit a resistance-temperature behavior characterized by flat minima even after eliminating the Kondo effect by oxidation of the impurities. The opposite signs of their thermoelectric potentials against a superconductor permit the preparation of ternary PdPtAu alloys free of a thermoelectric power. The measurements resulted in a nomogram suitable for determining the composition of the alloy necessary for a resistivity minimum at a given temperature between 1.5 and 4.2 K. Alloys manufactured in this way have a temperature coefficient of resistivity of less than 10(-6)/K within a temperature interval of 0.5 K and a thermoelectric power against a superconductor of less than 1 nV/K.     

热重分析仪TGA测定磁性材料的相转变

本文利用带有磁场的热重分析仪(M -TGA)对Fe3B合金中加入元素Nd造成的合金相转变和各相含量等进行研究。研究发现,在Fe3B合金中加入适量的稀土元素Nd将导致合金相组成由四角Fe3B(t-Fe3B)变为t-Fe3B和亚稳相Nd2 Fe2 3B3。与常规热分析仪器DTA相比,高灵敏的M -TGA可以更加清楚地观察到具有铁磁性转变的磁性材料相变过程     

High temperature Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin disk geometry

A versatile apparatus to measure the cross-plane Seebeck coefficient and the resistivity of bulk samples shaped as disks or thin plates, over a temperature range of 300 K-620 K with possible extension to higher temperatures, is presented. It is constructed from readily available equipment and instrumentation with parts that are easily manufactured. The Seebeck coefficient is measured over an average region of the sample under steady-state conditions. The sample resistance is measured using a four-point alternating current method and scaled to room temperature measurements with known geometry to calculate resistivity. A variety of sample shapes are supported. Most importantly, the support of the thin disk geometry allows for the very same samples to be used in a laser flash instrument. The design allows for rough vacuum, high vacuum, or purging with inert gases in the sample chamber. Measurements on thermoelectric ZnSb and a Ni reference material are presented.     

Ca对Mg-6Al合金微观组织和力学性能的影响

通过采用合金制备、组织分析、力学性能测试等手段,研究了Ca的加入对Mg-6Al合金微观组织和力学性能的影响。结果表明,适量Ca的加入能够细化合金组织,随着Ca加入量的增加,β-Mg17Al12相逐渐消失,并沿晶界析出了高熔点的Al2Ca相。同时,Ca的加入使得相形貌从细骨骼状逐渐演变为连续网状。3种工作温度的力学性能检测结果表明,随Ca的加入,试验合金的拉伸性能先增加后降低,且在Ca含量为0.5%、1%时,分别获得最佳室温和高温性能,但Ca的加入降低了整体的合金塑性。     

铝硅合金加锑变质机理的探讨

目前对锑在铝硅合金中的变质作用存在着不同的看法。本工作考察了加锑对铝硅合金的结晶过程,共晶硅相形貌的影响,并考察了锑在铝硅合金中的行径,而且与加钠的合金进行了对比。结果指出,加锑使共晶的形态有所改变,并在硅相中发现了Alsb化合物的存在,认为加Sb的作用是在熔体中析出弥散的AlSb晶体做为Si的异晶核。     

Ge-Sb-Te-O相变薄膜的光学性质研究

研究了单层 Ge- Sb- Te- O射频溅射薄膜在 40 0 nm～ 80 0 nm区域的光学常数 ( N,K)和反射、透射光谱 ,发现适当的氧掺杂能增加退火前后反射率对比度 ,因此 ,可以通过氧掺杂改良 Ge- Sb- Te相变材料的光存储性能     

铜含量对Super304H钢持久性能的影响

研究了铜含量对Super304H钢持久性能的影响，对铜在钢中的作用机理进行了探讨。结果表明，随铜含量的增加，钢的持久强度增加，在质量分数为4%时强度和塑性均达到最高。钢中的主要强化相为富铜相、M23C6、MC、M6C。在时效过程中，固溶于奥氏基体的铜以细小弥散球状富铜相的形式析出，形成富铜强化相。     

Relationship between the tribological properties of experimental aluminum alloys and their chemical composition

New complex alloying has been designed for aluminum antifriction alloys. Their tribological behavior has been determined, including the running-in ability, scoring resistance, and wear resistance. The interconnection of the tribological properties of experimental alloys with a doping level by different elements has been analyzed. Recommendations on the optimum content of alloying elements for the antifrictionality of the aluminum based alloys have been given.     

Quasicrystalline grain boundary precipitates in aluminium alloys through solid-solid transformations

We have observed the formation of icosahedral quasicrystals of Al-Mg-Zn, Al-Mg-Cu, Al-Li-Zn and Al-Li-Cu by low temperature annealing of solid solution alloys. The icosahedral phase particles form at the grain boundaries of the matrix alloys. The orientational relationships between the icosahedral crystallites, their corresponding Frank-Kaspar phase particles and the aluminium matrix are reported. The stability of the icosahedral phases is also discussed. Finally, the importance of grain boundary icosahedral phase particles to the physical properties of commercial aluminium alloys is pointed out.     

Effect of Ca addition on the microstructure and mechanical properties of as‐cast Mg–Sm alloys

This study investigated the effect of Ca addition on the microstructure and mechanical properties of as‐cast Mg–4Sm alloys. The addition of 1.0 wt% Ca led to a significant grain refinement of Mg–4.0Sm alloys owing to the formation of rod‐like Mg2Ca phases that acted as active nucleates for the Mg matrix. The as‐cast Mg–4.0Sm–1.0Ca alloy showed the smallest grain size at 45 μm. Furthermore, the Mg–4.0Sm–1.0Ca alloy exhibited greater hardness, higher tensile strength, and higher yield tensile strength and elongation than the other two alloys with different Ca contents. These results were attributed to the grain refinement and precipitation strengthening of the Mg2Ca and Mg41Sm5 phases. Microsc. Res. Tech. 79:707–711, 2016. © 2016 Wiley Periodicals, Inc.     

掺杂镧对TZM合金组织与性能的影响

采用粉末冶金法和轧制工艺制备了掺杂不同镧含量的TZM合金,研究了掺杂镧对不同状态TZM合金组织与力学性能的影响。结果表明:掺杂镧能显著细化TZM烧结坯的晶粒尺寸,La2O3掺杂量越多,细化效果越明显;掺杂镧可使TZM烧结坯的密度和硬度增大,显著提高TZM合金的强度和韧性,使其具有良好的力学性能。     

新型耐磨锌合金的轴承台架试验研究

通过在ZA27合金中添加Mn或Si等合金元素,制备出两种新型耐磨锌合金。相分析结果表明,它们的组织中含有较多弥散分布的硬质相,如含锰的金属间化合物或初生硅晶粒,这些硬质相的硬度远远高于ZA27合金中硬质点相ε。通过抗压性能测试和轴承台架试验,发现与两种传统的轴承合金ZA27和磷锡青铜ZCuSn10P1相比,新型耐磨锌合金的抗压性能良好、摩擦系数较低、滑动过程平稳、表面温升较低、耐磨性较好。新型锌合金优异的摩擦磨损性能与其耐磨微观组织有密切的关系。     

Crystalline phases found in rapidly quenched Ni–Nb–Zr alloys

The properties of metallic alloys can be significantly improved by developing non‐equilibrium phases in the microstructures through rapid solidification techniques, thus the characterisation of these unusual structures is extremely important. In this research, the microstructures of three rapidly quenched alloys, namely Ni_65.2Nb_33.8Zr_1.0, Ni_54.8Nb_31.1Zr_14.1 and Ni_54.8Nb_21.6Zr_23.6 (at. %) were investigated in greater detail in order to determine the structures and compositions of their crystalline phases. These crystalline phases were characterised using a combination of scanning electron microscopy, energy dispersive x‐ray spectroscopy, x‐ray diffraction and transmission electron microscopy techniques. The phases were compared to the crystalline structures reported in the literature. Our results indicate some agreement with the Ni–Nb phase diagram and an isothermal section of the Ni–Nb–Zr phase diagram; however, it is detected zirconium solubility in the Ni₃Nb phase, as well as, the absence of expected crystalline phases.     

新型无铅黄铜的耐蚀性能研究

采用脱锌腐蚀深度测量方法、光学显微镜、SEM和XRD等分析方法,研究了镁锑黄铜的脱锌腐蚀性能和添加少量Sn、Al元素对其耐腐蚀性能的影响。结果表明,镁锑黄铜的脱锌腐蚀首先发生在暴露于基体表面的β相,然后通过α相界扩展到另一个β相;当α相周围的β相和α相界脱Zn完全后,α相开始脱Zn。加Sn后,一方面强化了晶界,阻滞了α相的脱锌;另一方面Sn和Cu、O等元素构成了成分复杂的致密保护膜,阻止了基体Zn的溶解,有效地提高了镁锑黄铜的抗腐蚀性能。     

Electron crystallography applied to the structure determination of Nb(Cu,Al,X)2 Laves phases

The presence of primary precipitates of the Laves phases considerably improves the mechanical properties and the resistance to thermal degradation of the high‐temperature shape memory Cu–Al–Nb alloys. The structure analysis of the Laves phases was carried out on particles contained in the ternary and quaternary alloys as well on synthesized compounds related to the composition of the Nb(Cu,Al,X)₂ phase, where X = Ni, Co, Cr, Ti and Zr. The precise structure determination of the Laves phases was carried out by the electron crystallography method using the crisp software.     

用于热机械微纳加工的掺Al多晶硅加热器

针对热机械式微纳米结构的加工,提出了一种以掺Al多晶硅为材料,集成于微悬臂梁上的加热器.采用Al诱导退火晶化(AIC)方法,在750 K对Al/a-Si∶H复合薄膜低温晶化18 h,制备出掺Al多晶硅.通过低温退火,使复合薄膜的拉曼特征峰由478 cm-1移至520 cm-1,完成由非晶硅向多晶硅的转变;由四探针仪测得...     

Structure determination of the hexagonal quasicrystal approximant micro'-(Al,Si)4Cr by the strong reflections approach

A number of different crystalline phases have been found in Al-rich Al-Cr-Si alloys by transmission electron microscopy (TEM). Among these, the new hexagonal phase micro'-(Al,Si)(4)Cr (a=2.01 and c=1.24 nm) often found coexisting with the hexagonal micro-(Al,Si)(4)Cr (a=1.998 and c=2.4673 nm, isostructural with micro-Al(4)Mn) and also with the hexagonal lambda-(Al,Si)(4)Cr (a=2.839 and c=1.239 nm, isostructural with lambda-Al(4)Mn). It is evident from their electron diffraction patterns that the structures of these three phases are related. The strong reflections in all three are distributed in a similar way. They all exhibit a pseudo-icosahedral symmetry. The structure factor amplitudes and phases for the strong reflections of the micro' phase could therefore be adopted from those of the lambda phase, according to the strong reflections approach. A structure model of the micro' phase is thus deduced from the known lambda-Al(4)Mn. micro' consists of chains of 3+3 or 4+2 interpenetrated icosahedra along the 100 directions. Similar to the lambda phase, there are two flat layers (F) and four puckered layers (P) in each unit cell of micro', stacked along the c-axis in a sequence of PFP(PFP)' where the (PFP)' block is related to the PFP block by a 6(3) screw.     

A study on the mechanical properties of ti-8ta-3nb alloy for biomaterials

Ti-8Ta-3Nb has been developed as a new biomaterial. The experimental specimens are as-cast and forged Ti-8Ta-3Nb alloys. Treatment in a solution, ranging from 760 to 960°C has carried out. The microstructural research has carried out after the solution treatment and the hardness was measured. The specific heat and the length variations of Ti-8Ta-3Nb were also measured. The optimum temperature for the solution heat treatment of Ti-8Ta-3Nb was found to be 880°C. This was based on the mechanical properties and the volume fraction of α phase and their phases shown from the results of the solution heat treatment. From the results, the β transition temperature of Ti-8Ta-3Nb was found to be between 860° and 880°C.