High-Strength Granulated Titanium Alloys with the Intermetallic Type of Hardening

Creation of titanium-base high-strength high-temperature alloys is of great scientific interest. Alloy VT22 additionally alloyed with carbon or boron, or simultaneously alloyed with carbon and boron is considered, with the aim of estimating the effect of the degree of dispersity, shape, and uniformity of distribution of intermetallic phases (titanium carbides and borides) on the combination of physical and mechanical properties and the structure of titanium alloys with the intermetallic type of hardening. The test rods were fabricated by traditional (hot deformation of the ingot) and granule (hot isostatic pressing of granules hardened from the melt) methods. The granule process is shown to provide substantially finer segregations of intermetallic phases and their more uniform distribution in the structure, which results in an increase in the high-temperature and conventional strengths and in the creep resistance of the alloy.     

Microstructure and mechanical characteristics of VT1-0-Based composite material reinforced by titanium monoboride

The microstructure and mechanical characteristics of commercially pure titanium, i.e., the VT1-0 alloy, modified by 1.5 wt % B have been studied. It has been found that, during the melting of an ingot, uniformly distributed titanium monoboride (TiB) fibers up to Ø5 × 150 μm in size appear in the material in a volume fraction of about 8%. The results of compressive and tensile tests show that this composite material substantially surpasses pure titanium in the strength characteristics, with retaining satisfactory plasticity.     

Microstructure and Mechanical Properties of a Refractory CoCrMoNbTi High-Entropy Alloy

In this work, a new refractory high-entropy alloy, the Co-Cr-Mo-Nb-Ti system, was proposed as a family of candidate materials for high-temperature structural applications. CoCrMoNbTi _x (x values in terms of molar ratios, x = 0, 0.2, 0.4, 0.5 and 1.0) alloys were prepared by vacuum arc melting. The effects of variations in the Ti content on the phase constituents, microstructure and mechanical properties of the alloys were investigated using x-ray diffractometry, scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy and compressive testing. The results showed that the CoCrMoNbTi_0.4 alloy possessed a typical cast dendritic microstructure consisting of a single body-centered cubic (BCC) solid solution. Laves phases (Cr₂Nb and Co₂Ti) were formed in other alloys with different Ti contents. The results were discussed in terms of the mixing enthalpy, atomic size difference, electronegativity difference and valance electron concentrations among the elements within alloys. The alloy hardness exhibited a slightly decreasing trend as the Ti content increased, resulting from the coarser microstructure and reduced amount of Laves phases. Augmented Ti content increased the compressive strength, but decreased the ductility. Particularly, for the CoCrMoNbTi_0.2 alloy, the hardness, compressive strength and fracture strain were as high as 916.46 HV_0.5, 1906 MPa and 5.07%, respectively. The solid solution strengthening of the BCC matrix and the formation of hard Laves phases were two main factors contributing to alloy strengthening.     

AlCoCrFeNiBx 高熵合金微结构与性能

本文系统研究了 B 元素对高熵AlCoCrFeNiBx (x denotes the atomic fraction of B element 0, 0.1, 0.25, 0.5, 0.75 and 1.0)合金的微结构和性能的影响。其中添加的B元素含量为0.1时AlCoCrFeNi 高熵合金的形貌从等轴晶转变为枝晶形貌。 其中在等轴晶的内部可以观测到调幅分解结构。当 x>0.1时, 枝晶和调幅分解结构都逐渐消失了,但是越来越多的硼化物开始出现了。这个转变归因于 Cr-B 和Co-B之间高的负混合焓.随着B元素的增加, AlCoCrFeNiBx高熵合金的结构从B2 BCC 结构向B2 BCC FCC 结构的转变, 最后形成了 B2 BCC FCC 以及硼化物的混合结构。 随着B元素的添加硬度值从 HV486.0 下降到了 HV460.7, 然后增加到 HV615.7,其中x=0.1时合金的硬度最低。合金的压缩强度随B元素的增加明显下降,当x=0.25时,合金具有最大的压缩强度,但是当x =0.75时, 由于硼化物的大量生成合金在弹性变形阶段就发生了断裂。随着B含量增多合金的矫顽力和饱和磁化强度开始下降. 下降的矫顽力显示合金具有很好的软磁性能。     

原位合成多元硼化物对Al0.5CoCrCuFeNiBx高熵合金硬度与耐磨性能的影响

本文研究了Al0.5CoCrCuFeNiBx (x=0-1)的组织、相组成、硬度及耐磨性能。并预测了Al0.5CoCrCuFeNiBx (x=0-1)中简单固溶体形成规律。未添加硼元素的合金具有简单FCC固溶体结构。添加硼元素后,合金由简单FCC固溶体及多元硼化物组成。硼以硼化物形式析出,没有固溶到FCC固溶体中,因而添加硼对FCC固溶体的晶格常数无影响。硼化物的析出使合金的硬度提高,并且硬度随着硼含量的增加而呈线性增加。当硼含量x?0.4时,合多的磨耗阻变化不明显,但当硼含量x?0.6时,合金的磨耗阻抗随着硼含量增加而呈线性增加。 随着硼含量的增加,合金的磨损机制由粘着磨损转变为氧化磨损。合金硬度与耐磨性能的提高是高硬度的粗大硼化物与韧性的FCC固溶体基体共同作用的结果。     

MICROSTRUCTURE AND PROPERTIES OF HIGH BORON BEARING STEEL

1. IntroductionShieldi11g lnaterials play an ilnporta11t role iu the national defence a11d nuclear powerplal1ts. Recently, great efforts have bee1l 1nade on its developnlentll'2]. It's well known thatboron has pron1ising hot lleutrol1 absorptioll properti…     

Structure and mechancal properties of titanium alloy VT35 in the cast condition

Conclusion In a large ingot (1 ton) of alloy VT35 the distribution of chemical elements both over the cross section and over the height is uniform, the macrostructure of the ingot is similar to the structure of other two-phase titanium alloys, and the microstructure is almost the same in different parts of an ingot. The mechanical properties in different parts of an ingot are the same, i.e., the strength is low and the ductility is significant. All of this points to the high promising cast properties of alloy VT35 and also that there should not be any complicated technical problems connected with chemical inhomogeneity.Scientific Research Institute of Aviation Materials, Moscow. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 36–38, September, 1993.     

硼含量对Fe-B-C合金组织和性能的影响

研究了含0.5％～2.0％B的Fe-B-C合金在铸态和热处理态下组织和硬度的变化规律.试验结果表明,硼含量为0.5％及碳含量为0.14％的Fe-B-C铸态合金,显微组织结构简单,无共晶硼化物生成,硬度低.随着硼含量的继续增加,在晶界处生成共晶硼化物,呈网状结构分布,晶粒度不均匀.经淬火处理后,网状结构出现断网,当淬火温度达到950℃时,断网明显,组织并无粗化现象,硬度达到47 HRC,此时性能为实验条件下最优.随着淬火加热温度的升高,热处理组织粗大,硬度略有下降.以显微组织和硬度为评价标准时,硼含量为1.5％,淬火温度为950℃,综合性能较好.     

含B量对激光熔覆FeCoCrNiB_x(x=0.5,0.75,1.0,1.25)高熵合金涂层组织结构与耐磨性的影响

采用激光熔覆技术制备FeCoCrNiBx高熵合金涂层,用X射线衍射(XRD)、扫描电镜(SEM)、硬度和耐磨测试等方法,研究了B含量对激光熔覆FeCoCrNiBx高熵合金涂层的组织结构、硬度和耐磨性能的影响。结果表明,随B含量的增加,合金相结构逐渐由fcc固溶体结构转变为fcc固溶体和M3B相共存,M3B相主要为Cr、Fe硼化物。随B含量的增加,枝晶组织中析出颗粒状和短棒状的M3B相,且M3B相逐渐长大成长条状。B的增加显著提高合金涂层的硬度,由4470 MPa增加到8480 MPa,且磨损量随着B的增加而减少。     

Optimization of the composition, structure, and properties of electrode materials and electrospark coatings for strengthening and reconditioningof metal surfaces

The structure and phase composition of Ni-Cr-Al alloys doped with Si, Ti, Mn, and Co have been studied. An eutectic three-phase structure was found to be in the doped alloys. Doping with Si and Ti increases the microhardness and wear resistance of the alloys. The highest coefficient of the mass transfer (0.75) during the electrospark alloying is observed for Co-containig alloys. The coatings with the doped alloys have a higher wear resistance than those with the Ni-Cr-Al basic alloy. Steel 45’s heat resistance is increased after the electrospark doping with Si-, Ti-, Mn-, and Co-containing alloys by 4, 4.3, 5.1, and 4.6 times, respectively. The electrode materials have been developed for the electrospark reconditioning of workpieces based on PE8418 (Ni-Ni₃B-Cu-Si) with the additions of titanium carbide, chromium carbide, and tungsten carbide, which make it possible to manufacture coatings up to 5-mm thick. The results of the investigation of the erosion properties of B₄C-TiB₂ alloys manufactured using the method of reactive sintering under hot pressing of B₄C-TiO₂ powder blends that were used as the electrode materials for the electrospark hardening of titanium surfaces are presented. The tests show that, in the surface layers of the electrode materials, under the impact of the electric discharge, the boron carbide content substantially decreased, while the quantity of titanium borides increased and new phases of TiC _x N _y , TiO₂, and Ti appeared. Only these components are transferred onto the surface of the titanium alloy and form there a protective coating up to 100 μm thick with high hardness (32–43 GPa) and wear resistance. The materials developed are promising for their application as the electrodes in the electrospark alloying of construction steels and titanium alloys.     

Development of boron white cast iron

Abstract

With boron substituting for carbon in cast iron composition and eutectic borides substituting for eutectic carbides in microstructure as the hard wear resistant phase, a new kind of wear resistant white cast iron has been developed. The microstructure and mechanical properties of this new white cast iron both in the as cast state and after appropriate heat treatments were studied. The results show that the as cast microstructure of the boron white cast iron comprises a dendritic matrix and interdendritic eutectics, and the eutectic compound is that of M₂B or M′_0˙9Cr_1˙1B_0˙9 type, where M represents Fe, Cr or Mn and M′ represents Fe or Mn. The morphology of the eutectic borides is much like that of carbide in high chromium white cast iron, but the hardness of boride is higher than that of carbide. The matrix in as cast microstructure comprises martensite and pearlite. After austenitising and quenching, the matrix mostly changes to lath type martensite and the eutectic borides remain unchanged. In addition, two different sizes of particles, with different forming processes during heat treatment, appear in the matrix. The boron white cast iron possesses higher hardness and toughness than conventional white cast iron and nickel hard white cast iron, and has a better balance between hardness and toughness than high chromium white cast iron.     

Effects of rare earth elements on the microstructure and mechanical properties of NiAl-based eutectic alloy

The effects of rare earth elements (REEs) (like Y, Ce, Nd and Dy) on the microstructure and mechanical properties of cast NiAl–28Cr–5.5Mo–0.5Hf alloy were investigated. The results suggest that the microstructure of REEs-doped alloys gradually refines with increasing REEs addition and the appropriate addition of REEs can improve the compressive ductility and yield strength at room temperature. In addition, REEs additions increase the elevated temperature strength and deformation ability of the alloys. The elevated temperature compression deformation behavior of Nd-doped alloy can be properly described by power-law equation.     

Influence of boron and oxygen on the microstructure and mechanical properties of high-strength Ti66Nb13Cu8Ni6.8Al6.2 alloys

The influence of boron additions and different oxygen contamination levels on the microstructure and the mechanical properties in the Ti_66?xNb₁₃Cu₈Ni_6.8Al_6.2B_x (0 ? x ? 1) system were investigated. The alloys were prepared by levitation copper mould casting as rods with a diameter of 5 mm using different grades of starting elements. The alloy without boron exhibits a maximum compressive stress of more than 2500 MPa, associated with a compressive strain of more than 30%. The ultimate tensile stress is ～1075 MPa with a maximum elongation of 1.6%. Increased oxygen content leads to a rise of yield strength due to solid solution hardening. Boron additions promote grain refinement and reinforce the interdendritic phase compound by forming needle-like TiB precipitates. This change in microstructure increases the yield stress and the Young’s modulus and lowers the plastic strain. The microstructure was analysed in terms of the boron content by means of scanning electron microscopy, Auger electron spectroscopy and transmission electron microscopy. The presented mechanical properties are compared with the compression and tensile properties of the commercially available Ti6Al4V ELI (ELI = extra low interstitial) alloy.     

高强β钛合金热变形过程中组织演变及热加工图研究进展（英文）

高强度β钛合金广泛应用于航空领域的大型承重部件。目前,大型零件一般采用模锻成型。不同的初始显微组织和变形工艺参数会显著影响流动行为。为了实现显微组织的精确控制,研究人员进行了大量的研究工作去分析热压缩过程中的组织演变和变形机制。本文重点综述高强度β钛合金在热变形过程中的组织演变,包括单相区的动态再结晶和动态回复,以及两相区中α相的动态演变。此外,总结热加工图中的最佳热加工区域、不稳定区域以及功率耗散效率与变形机制之间的关系。最后,强调利用热加工图优化工艺参数存在的问题和发展方向。     

微量B对Mg-3A1-1Zn镁合金组织和性能的影响

B通过Al-3B中间舍金加入Mg-3Al-1Zn舍金中，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。舍金的力学性能和耐腐蚀性能也随B加入量的增加而降低。     

硼对低钴AB5型贮氢合金循环寿命的影响

为了提高低钴AB5型贮氢合金的电化学循环稳定性，在低钴AB5型贮氢合金中加入微量的硼，用真空快淬工艺制备了稀土系低钴AB5型MmNi3.8Co0.4Mn0.6Al0.2Bx(x=0，0．1，0．2，0．3，0．4)贮氢合金，分析测试了铸态及快淬态合金的电化学性能及微观结构，研究了硼对铸态及快淬态合金微观结构及循环寿命的影响。结果表明，硼能大幅度提高铸态及快淬态低钴AB5型贮氢合金的电化学循环稳定性，但其作用机理是完全不同的。     

Formation of submicrocrystalline structure in titanium and titanium alloys and their mechanical properties

The effect of deformation temperature on the grain size in titanium VT1-0 and double-phase titanium alloy VT6 is studied. The temperature-and-rate modes of formation of submicrocrystalline structure are determined. The mechanical behavior and the evolution of the microstructure in the course of warm severe deformation is investigated by means of successive compression of specimens over three orthogonal directions at a temperature of 400°C for titanium and 550°C for alloy VT6. The mechanisms of grain refinement in severe deformation are determined. It is shown that they differ depending on the composition of the alloy. The method of “abc”-deformation is used for fabricating large-mass preforms from titanium VT1-0 and alloy VT6 with submicrocrystalline structure; large-size sheets are produced from alloy VT6. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 19–26, February, 2006. Grant of Russian foundation for fundamental research No. 05-08-65396-a.     

Investigations on Microstructures and Toughness of Fe-B Cast Alloy Containing Titanium and Nitrogen

The effects of titanium and nitrogen elements on the microstructure and impact toughness of the Fe-B alloy have been studied. The results show that the borides are refined after the additions of titanium and nitrogen elements. With the additions of titanium and nitrogen, titanium nitrides are formed in the Fe-B alloy. Titanium nitride can act as effective heterogeneous nuclei of primary austenite, and promote the refinement of austenite and boride. After heat treatment, the impact toughness of Fe-B alloys modified by titanium and nitrogen elements is higher than that of ordinary alloy.     

Effect of Cr on Microstructure and Properties of a Series of AlTiCr x FeCoNiCu High-Entropy Alloys

A series of AlTiCr _x FeCoNiCu (x: molar ratio, x = 0.5, 1.0, 1.5, 2.0, 2.5) high-entropy alloys (HEAs) were prepared by vacuum arc furnace. These alloys consist of α-phase, β-phase, and γ-phase. These phases are solid solutions. The structure of α-phase and γ-phase is face-centered cubic structure and that of β-phase is body-centered cubic (BCC) structure. There are four typical cast organizations in these alloys such as petal organization (α-phase), chrysanthemum organization (α-phase + β-phase), dendrite (β-phase), and inter-dendrite (γ-phase). The solidification mode of these alloys is affected by Chromium. If γ-phase is not considered, AlTiCr_0.5FeCoNiCu and AlTiCrFeCoNiCu belong to hypoeutectic alloys; AlTiCr_1.5FeCoNiCu, AlTiCr_2.0FeCoNiCu, and AlTiCr_2.5FeCoNiCu belong to hypereutectic alloys. The cast organizations of these alloys consist of pro-eutectic phase and eutectic structure (α + β). Compact eutectic structure and a certain amount of fine β-phase with uniform distribution are useful to improve the microhardness of the HEAs. More γ-phase and the microstructure with similar volume ratio values of α-phase and β-phase improve the compressive strength and toughness of these alloys. The compressive fracture of the series of AlTiCr _x FeCoNiCu HEAs shows brittle characteristics, suggesting that these HEAs are brittle materials.     

Structure and microhardness of granules of VT22 alloy additionally alloyed with carbon and boron

The use of various methods of rapid hardening of melts opens wide possibilities for creating new titanium alloys strengthened by intermetallic compounds that possess elevated heat and creep resistances, strength, and other characteristics. The present paper concerns the regular features in the decomposition of alloy VT22 (in the form of granules) rapidly hardened from the liquid state and alloyed additionally with carbon and boron.