Microstructure and Mechanical Behavior of CrFeNi2V0.sWx (x=0, 0.25)High-Entropy Alloys

CrFeNi₂V_0.5W_x (x = 0, 0.25) alloys based on these parameters of mixing enthalpy (ΔH_mix), mixing entropy (ΔS_mix), atomic radius difference (δ), valance electron concentration, and electronegativity difference(Δχ) were designed and prepared. The microstructure and room-temperature mechanical behavior of both alloys were investigated. Compressive test results showed that the CrFeNi₂V_0.5W_0.25 alloy had higher yield strength than that of the W-free CrFeNi₂V_0.5 alloy, although they all exhibited quite larger compressive plasticity (ε > 70%). Compression fracture surface of CrFeNi₂V_0.5W_0.25 alloy revealed a ductile fracture in the face-centered cubic (FCC) phase and a brittle-like fracture in the σ phase. Moreover, tensile test results indicated that the CrFeNi₂V_0.5W_0.25 alloy exhibited excellent mechanical property with an ultimate tensile strength of 640 MPa and a high tensile elongation of 15.7%. The tensile deformation mode of the FCC phase in the CrFeNi₂V_0.5W_0.25 alloy is dominated by planar glide, relating to dislocation configurations, high-density dislocations, and dislocation wall. Therefore, dislocation slip plays a significant role in tensile deformation of CrFeNi₂V_0.5W_0.25 high-entropy alloy. The higher strength of CrFeNi₂V_0.5W_0.25 alloy is predominantly due to the solid solution strengthening of W element and σ phase precipitation strengthening. Combination of the higher tensile strength and plasticity suggests that the CrFeNi₂V_0.5W_0.25 alloy can be a promising aerospace material.     

CrFeCoNiB0.05Tix高熵合金的显微组织和力学性能

采用机械合金化和放电等离子烧结工艺制备了CrFeCoNiB_0.05Ti_x(x=0.2、0.4、0.6、0.8、1.0)高熵合金材料,通过X射线衍射分析、扫描电镜观察和能谱分析以及维氏硬度测试和压缩强度测试等,研究了Ti含量对高熵合金微观组织和力学性能的影响。结果表明,CrFeCoNiB_0.05Ti_x(x=0.2、0.4、0.6、0.8、1.0)高熵合金由FCC、BCC和α相组成。当x=1.0时,合金由BCC结构转向HCP结构并析出新相Laves相,其具有最高硬度416.54 HV0.2。当x=0.8时,合金达到最大抗压强度586.3 MPa。     

Al含量对热轧FeMnCoCr系高熵合金组织和性能的影响

研究了Al含量对(Fe₅₀Mn₃₀Co₁₀Cr₁₀)_100-xAl_x高熵合金微观组织、变形机制和拉伸性能的影响。采用真空电弧熔炼炉制备合金铸锭,对合金进行压下率为80%的热轧火淬,利用SEM和EBSD对合金的组织结构进行了分析。结果表明,随着Al含量(原子分数,下同)由0%增加到6%,热轧淬火后合金组织由FCC+HCP双相转变成FCC单相,Al含量为8%时产生了BCC相;随着Al含量由0%增加到6%,在拉伸过程中TRIP效应受到抑制,TWIP效应明显增加,合金的屈服强度变化不大,抗拉强度稍有降低,断后伸长率显著增加,当Al含量为6%时断后伸长率达到最高,为79%。     

TA2/ Co13Cr28Cu31Ni28/ Q235脉冲TIG焊接头组织与性能

针对钢与钛之间因物化性能差异大,焊接过程易产生大量金属间化合物而难以实现可靠连接的问题,依据焊缝金属固溶高熵化思路,选用Co₁₃Cr₂₈Cu₃₁Ni₂₈高熵合金作为中间过渡层对TA2钛和Q235钢进行脉冲钨极氩弧焊,并对Co₁₃Cr₂₈Cu₃₁Ni₂₈高熵合金及接头的组织和性能进行分析研究. 结果表明,Co₁₃Cr₂₈Cu₃₁Ni₂₈主要是双相面心立方结构,分别为富Cu的晶间和晶内面心立方结构,强度和塑性良好;焊接接头两部分焊缝均成形良好,无气孔、裂纹等缺陷,焊缝组织均为简单的固溶体结构,Q235侧焊缝主要为面心立方结构相,TA2侧焊缝主要由简单的体心立方结构和面心立方结构相构成,以体心立方结构相为主;焊接接头抗拉强度为224 MPa,在TA2侧靠近高熵合金的熔合线处断裂,主要由于生成了脆性的Cr₃O₈,断口有较多韧窝和一部分解理面,为混合断裂,表现出一定的韧性断裂特征.     

Tix(AlNbZr)100-x系多主元合金力学性能的第一性原理研究

通过对合金的固溶体参数以及相比例图进行计算,研究了Ti_x(AlNbZr)_100-x系多主元合金的固溶体相形成规律,运用基于密度泛函理论的第一性原理方法研究了Ti含量变化对Ti_x(AlNbZr)_100-x系多主元合金结构稳定性以及力学性能的影响。结果表明,Ti_x(AlNbZr)_100-x系多主元合金可以形成稳定的固溶体相,且合金主要由BCC相和Al₃Zr₅相组成,随Ti含量增加,合金的液相线降低,Al₃Zr₅相的相形成温度减小,直到Ti含量为60%~70%时,Al₃Zr₅相消失,合金由单一BCC相组成;Ti含量增加可以提高合金的结构稳定性,当Ti含量为25%~70%时,合金具有良好的力学稳定性,合金的体积模量、剪切模量以及杨氏模量随着Ti含量的增加呈上升趋势。Ti_x(AlNbZr)_100-x系多主元合金的基态能量和形成热随着Ti含量的增加而降低,表明增加Ti含量可以增加该合金系的热力学稳定性,使合金更易形成固溶体相。     

激光熔覆AlxNbMn2FeMoTi0.5高熵合金涂层的组织与性能

使用激光熔覆技术在Q235钢基体上制备Al_xNbMn₂FeMoTi_0.5高熵合金涂层,期望借此提高干切削技术适用刀具表层的硬度和耐磨性。经过初步筛选之后,主要研究了Al_xNbMn₂FeMoTi_0.5(x=1、1.5、2)高熵合金涂层体系,并采用XRD和3D激光扫描成像等手段分析了不同Al含量的Al_xNbMn₂FeMoTi_0.5合金涂层的晶相结构、显微组织和具体元素分布。结果显示,对于Al_xNbMn₂FeMoTi_0.5高熵合金涂层,随着Al含量的增加,涂层的相结构由单一的BCC相逐渐转变为双相BCC结构,晶粒逐渐细化。当x=2时,Al_xNbMn₂FeMoTi_0.5高熵合金涂层硬度最高,平均为1089.6 HV0.3,大约为基材的5倍,且其具有最优的耐磨损性能。x=1.5时,Al_xNbMn₂FeMoTi_0.5高熵合金涂层的自腐蚀电位最高,自腐蚀电流密度最小,耐腐蚀性最好。     

基于第一性原理的CrCuFeNiTi高熵合金涂层的相及稳定性分析

采用等离子弧在45钢基体上熔覆了CrCuFeNiTi高熵合金涂层,经X射线衍射分析涂层中的物相有BCC、FCC和Fe₂Ti相,并对BCC、FCC和Fe₂Ti相进行了成分测试,采用CASTEP中的虚拟晶体近似方法建立了BCC、FCC和Fe₂Ti相的晶体结构模型,基于第一性原理计算了涂层中BCC、FCC和Fe₂Ti相的晶格常数,并与涂层中BCC、FCC和Fe₂Ti相的X射线测试结果进行了比较,另外计算了BCC和FCC相的弹性常数C_ij、体积模量B、剪切模量G、杨氏模量E和泊松比ν。结果表明,涂层中BCC和FCC相以及Fe₂Ti的晶格常数计算值与试验值的误差为0.43%~3.05%,BCC、FCC和Fe₂Ti相的生成热均为负值且BCC和FCC相的弹性常数C₁₁、C₁₂和C₄₄满足立方结构高熵合金的力学稳定性限制条件,可知BCC、FCC和Fe₂Ti相是稳定的。另外由C₁₂-C₄₄>0,G/B<0.57,ν>0.26可知BCC和FCC相以金属键结合且呈现韧性的特征。     

(FeCoNiCr)100-xMnx高熵合金在NaCl和NaOH溶液中的抗腐蚀性能

研究了放电等离子烧结(FeCoNiCr)_100-xMn_x(x=4,8,12,20)高熵合金的组织结构及在NaCl和NaOH溶液中的耐腐蚀性能。结果表明,(FeCoNiCr)_100-xMn_x合金主要由FCC单相组织和少量BCC相组成。(FeCoNiCr)₈₈Mn₁₂合金在3.5wt%NaCl 溶液中具有最好的耐腐蚀性能。Mn的添加使合金在1 mol NaOH 溶液中耐腐蚀性增强。退火对合金在1 mol NaOH 溶液中抗腐蚀性能影响不大。(FeCoNiCr)_100-xMn_x合金在3.5wt%NaCl溶液和1 mol NaOH溶液中的抗腐蚀性能均优于304S不锈钢。     

Effect of Nb Content on Microstructure and Mechanical Properties of Mo0.25V0.25Ti1.5Zr0.5Nbx High-Entropy Alloys

High-entropy alloys (HEAs) have significant application prospects as promising candidate materials for nuclear industry due to their excellent mechanical properties, corrosion resistance and irradiation resistance. In this work, the Mo_0.25V_0.25Ti_1.5Zr_0.5Nb_x(x=0, 0.25, 0.5, 0.75 and 1.0) HEAs were designed and fabricated. The alloys were prepared by vacuum arc melting, and all the ingots were annealed at 1200°C for 24 h. The microstructures, ...     

First-Principles Investigation on Phase Stability,Elastic and Magnetic Properties of Boron Doping in Ni-Mn-Ti Alloy

The all-d-metal Ni-Mn-Ti Heusler alloy has giant elastocaloric effect and excellent mechanical properties, which is different from the conventional Ni-Mn-based Heusler alloys. In this work, the preferred site occupation, phase stability, martensitic transformation, magnetic properties, and electronic structure of the B-doped Ni₂Mn_1.5Ti_0.5 alloys are systematically investigated by the first-principles calculations. The results show that B atoms preferentially occupy the octahedral interstitial. The doped B atoms tend to exist in the (Ni₂Mn_1.5Ti_0.5)_1-xB_x (x = 0.03, 0.06, 0.09) alloy in the form of aggregation distribution, and the martensitic transformation temperature decreases with the increase in the B content. For octahedral interstitial doping, the toughness and plasticity of the (Ni₂Mn_1.5Ti_0.5)_1-xB_x alloys decrease, but the strength and rigidity are greatly enhanced. This is because a small part of the d-d hybridization in ternary Ni-Mn-Ti alloy is replaced by the p-d hybridization in Ni-Mn-Ti-B alloy.     

Synthetic Effect of Cr and Mo Elements on Microstructure and Properties of Laser Cladding NiCrxMoy Alloy Coatings

NiCr_xMo_y (x = 1, 1.5; y = 0, 0.1, 0.3) alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon. The phase composition, microstructure, corrosion behavior, and mechanical properties of the NiCr_xMo_y alloy coatings were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electrochemical tests, X-ray photoelectron spectroscopy, microhardness, and nanoindentation tests. As the Cr content increased, the phase composition of the coatings changed from a single face-centered cubic (FCC) structure to a dual-phase structure coexisting with body-centered cubic (BCC) and FCC structures, while the addition of Mo promoted the precipitation of σ phase. The appearance of a homogeneous dual-phase structure and some amount of σ phase played a positive role in the corrosion resistance of NiCr_xMo_y coatings. Cr³⁺ ions and Mo⁶⁺ ions in the passive film enhanced the stability of the coatings. The nanoindentation tests showed that the nanohardness (6.71 GPa) and elastic modulus (184.40 GPa) of BCC phase were higher than those of the FCC phase (5.19 GPa and 155.26 GPa, respectively). Overall, the BCC phase and σ phase improved the mechanical properties of the coatings.     

Synergistic effect between Laves phase and Zr-Ni phases in Zr(MnVNi)2 hydrogen storage alloys

The effect of annealing treatment on the crystal structure and electrochemical properties of Zr(Mn_0.25V_0.20Ni_0.55)₂ and Zr(Mn_0.05V_0.40Ni_0.55)₂ hydrogen storage alloys was investigated by means of XRD analysis and electrochemical tests. The results of XRD analysis showed that the as-cast alloys consist of C15, C14 type Laves phase and Zr₉Ni₁₁ and ZrNi phases. The composition of alloys homogenized after annealing treatment. The C15 type Laves phase is still stable while the Zr₉Ni₁₁ and ZrNi phases decompose and C14 phase disappears partially. The final stable structure of the alloys was a mixture phase of C15 and C14 type Laves phases. The results of the electrochemical tests showed that the discharge capacity and the properties of activation as well as high-rate dischargeability are all decreased after annealing treatment. The exchange current density decreases in some degree too.     

粉末冶金FeCoNiCu0.4Al0.4高熵合金的热处理组织与性能

采用机械合金化(MA)与放电等离子烧结(SPS)相结合的方法制备出FeCoNiCu0.4Al0.4高熵合金,研究不同热处理温度对合金显微组织与力学性能的影响规律。结果表明:机械合金化后,FeCoNiCu0.4Al0.4高熵合金形成了单相的FCC固溶体,经1100℃SPS烧结后的块体组织仍为单相FCC结构,其压缩屈服强度、塑性应变和显微硬度分别为1165.1 MPa、45.2%和356.9 HV。经过热处理后,合金组织中生成了新的BCC相,且BCC相的含量随热处理温度的升高先增多后减少,500、600和700℃热处理后BCC相的含量分别为7%、30%和21%(体积分数)。退火态FeCoNiCu0.4Al0.4高熵合金的屈服强度随热处理温度的升高先升高后降低。当BCC相含量增多时,材料的屈服强度和硬度相应地提高,而塑性却显著降低。     

A comparative study on the hydriding kinetics of Zr-based AB2 hydrogen storage alloys

Two kinetic models (Jander model and Chou model) are used to investigate the hydrogen absorption kinetic mechanism of Zr-based AB₂ type Laves phase alloys (Ti_0.1Zr_0.9Mn_0.9V_0.1Fe_0.5Co_0.5, Ti_0.1Zr_0.9(Mn_0.9V_0.1)_1.1Fe_0.5Ni_0.5 and Ti_0.1Zr_0.9Mn_0.9V_0.1Fe_0.55Ni_0.55). The analysis shows that the rate-controlling step is the diffusion process at high temperatures in the range from 673 K to 923 K with a low hydrogen concentration (solid solution phase). Both models can well describe the experimental data but Chou model is preferred. Chou model is simpler and easier to use for analyzing the experimental results. The activation energies calculated using Chou model with the least square method are 29.3 kJ/mol H₂ for Ti_0.1Zr_0.9Mn_0.9V_0.1Fe_0.5Co_0.5, 43.8 kJ/mol H₂ for Ti_0.1Zr_0.9(Mn_0.9V_0.1)_1.1Fe_0.5Ni_0.5 and 48.5 kJ/mol H₂ for Ti_0.1Zr_0.9Mn_0.9V_0.1Fe_0.55Ni_0.55, which are close to the values reported in the literature (28.3 kJ/mol H₂ for Ti_0.1Zr_0.9Mn_0.9V_0.1Fe_0.5Co_0.5 and 40.3 ± 1.5 kJ/mol H₂ for both Ti_0.1Zr_0.9(Mn_0.9V_0.1)_1.1Fe_0.5Ni_0.5 and Ti_0.1Zr_0.9Mn_0.9V_0.1Fe_0.55Ni_0.55).     

Effects of Tungsten Addition on the Microstructure and Mechanical Properties of Near-Eutectic AlCoCrFeNi<Subscript>2</Subscript> High-Entropy Alloy

The effects of tungsten addition on the microstructure and mechanical properties of near-eutectic AlCoCrFeNi₂ high-entropy alloy were investigated in this paper. The AlCoCrFeNi₂W _x alloys comprised the primary BCC phase plus eutectic FCC/BCC phases. It was found that W element can both promote the formation of the primary BCC phase and act as a solid solution strengthening element. The hardness of the AlCoCrFeNi₂W _x alloys increased from HV 293 to HV 356.2 with the increase in W content. The addition of W element improved the strength of alloys but reduced ductility. Thereinto, the AlCoCrFeNi₂W_0.2 alloy showed the most excellent compressive properties with the fracture strength of 2785.9 MPa and the plastic strain of 0.42, respectively, which implied the potential industrial application values.     

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。     

Designing Rules of Laser-Clad High-Entropy Alloy Coatings with Simple Solid Solution Phases

The criteria of process parameters(μ≤4),atomic size difference(ε≤5.8,δ≤11 and α≤2),thermodynamic(-14.5 ≤△H_(mix)≤6.5 and Ω≥ 1.8) in the prediction of the phase stability for laser-clad high-entropy alloy coatings are studied in detail.Besides,the criteria of valence electron concentration(VEC) applied to distinguish the stability of different solid solution phases are as follows:VEC7.65 for simple BCC,VEC≥7.65 for simple face-centered cubic(FCC),7.14 VEC 7.78 for dual-phase BCC and FCC.Among them, μ and ε proposed firstly separate the phase stability of laserclad high-entropy alloy coatings quite precisely.The other modified criteria(δ,α,△H_(mix),Ω,VEC) are proved to be different from those of the high-entropy alloys synthesized by the traditional casting and smelting processes.     

Microstructure and dry sliding wear resistance of Moss-toughened Mo2Ni3Si metal silicide alloys

A wear resistant Mo₂Ni₃Si-based metal silicide alloy toughened by molybdenum-based solid solution (Mo_ss) was fabricated by the laser melting deposition (LMD) manufacturing process. Microstructure of the alloy is composed of Mo_ss primary dendrites and the matrix of the single phase Mo₂Ni₃Si. Wear resistance and friction coefficient of the alloys were evaluated under metallic dry sliding wear test conditions as a function of contact load. Results showed that the alloys have a low friction coefficient and outstanding wear resistance due to the high hardness of Mo₂Ni₃Si matrix and the high strength, ductility and toughness of Mo_ss dendrites. The wear rate and the friction coefficient of alloys are extremely insensitive to the contact load owing to the abnormal hardness–temperature relation of Mo₂Ni₃Si. The Mo_ss dendrite played the role of trapping micro-cracks and restraining brittle spalling of the Mo₂Ni₃Si matrix during wear process and improved the wear properties of Mo_ss-toughened Mo₂Ni₃Si alloy.     

Microstructural Evolution of Co35Cr25Fe30Ni10 TRIP Complex Concentrated Alloy with the Addition of Minor Cu and Its Effect on Mechanical Properties

The in?uences of minor Cu addition (2 and 4 at.%) on the microstructural evolution and room-temperature mechanical property of metastable Co ₃₅ Cr ₂₅ Fe ₃₀ Ni ₁₀ are systemically investigated in the present study. The results indicate that the thermally induced hexagonal close-packed (HCP) phase is absent when Cu was added, due to the increase in stacking fault energy (SFE). The 2%-Cu-added alloys showed the largest total elongation of 69% among the ...     

Electron microscopy and X-ray diffraction studies of rapidly quenched Zr---Ni and Hf---Ni ribbons with about 90 at.% Ni

The structure of melt-spun ribbons of the alloys Zr₉Ni₉₁, Zr₁₀Ni₉₀ and Hf₁₁Ni₈₉ was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ribbons of the Zr₉Ni₉₁ and Zr₁₀Ni₉₀ alloys prepared at a high cooling rate (ribbon thickness d=11 μm) were characterized by an amorphous matrix with a few per cent of quenched-in crystallites. The ribbon of the Hf₁₁Ni₈₉ alloy prepared with the same thickness (i.e. at the same cooling rate) exhibited a nanocrystalline grain structure of the HfNi₅ phase. Thicker ribbons of the Zr₉Ni₉₁ alloy (d=17–22 μm), for which the quench rate was correspondingly lower, were obtained as a b.c.c. Ni(Zr) solid solution phase with a grain size of nearly 1 μm. A high resolution (HR) TEM study of one of the Zr₉Ni₉₁ crystalline ribbons revealed a fine structure of the interior of the crystallites which can be attributed to an ordering on the Zr sublattice over distances of several nanometres within the b.c.c. grains.