冷轧退火对FeMnCoCrAl高熵合金组织和力学性能的影响

使用真空电弧炉熔炼出(Fe₅₀Mn₃₀Co₁₀Cr₁₀)₉₄Al₆合金,利用冷轧及在不同温度对合金进行退火,以期望得到由多尺度再结晶晶粒构成的层状结构;并对不同退火温度的样品进行拉伸性能测试。利用扫描电镜和EBSD对合金组织形貌进行表征,采用X射线衍射方法研究其相组成。结果表明:合金在铸态和冷轧后相组成未发生变化,700 ℃退火得到较好的多尺度再结晶晶粒的层状结构,其屈服强度为487 MPa,抗拉强度为708 MPa,断后伸长率为39%,表现出良好的综合力学性能。     

铸态(Fe33Cr36Co15Ni15Ti1)96Al4高熵合金力学性能及腐蚀行为

利用经典高熵合金判据设计了一种非等摩尔比(Fe₃₃Cr₃₆Co₁₅Ni₁₅Ti₁)₉₆Al₄高熵合金。利用X射线衍射仪、扫描电子显微镜、能谱仪、万能力学试验机和电化学工作站对合金的晶体结构、微观组织、元素分布、力学性能(压缩和拉伸性能)及腐蚀性能进行了研究。结果表明,(Fe₃₃Cr₃₆Co₁₅Ni₁₅Ti₁)₉₆Al₄高熵合金为FCC+BCC双相结构,合金微观组织为枝晶组织,室温下合金抗压强度为743 MPa及超过50%的压缩应变,而拉伸屈服强度、抗拉强度、伸长率分别为591 MPa、984 MPa和15.8%,其断裂机制为韧性断裂。合金表现出优于304SS的耐蚀性,点蚀电位为846 mV,约是304SS的三倍。     

冷轧和退火对Ni40(FeCoCrAl)60高熵合金组织与性能的影响

研究了高温退火和二次退火对冷轧后Ni₄₀(FeCoCrAl)₆₀高熵合金组织和性能的影响。结果表明,铸态合金由FCC+BCC双相组成。冷轧并再结晶后,合金保持稳定的相结构,FCC相由树枝晶转变为等轴晶,BCC相位于FCC相之间和FCC相之内。铸态合金的屈服强度和抗拉强度分别为450 MPa和870 MPa,伸长率为40%。室温冷轧后合金强度显著升高,屈服强度和抗拉强度分别是铸态合金的2.9倍和1.7倍,伸长率降至4%。再结晶退火使屈服强度和抗拉强度分别降为590 MPa和820 MPa,伸长率为12%。     

异质结构CoCrFeNiW高熵合金的拉伸性能和强化行为（英文）

采用真空电弧熔炼方法制备Co₃₀Cr₃₀(FeNi)_40-xW_x(x=0～8%(摩尔分数),分别简化为HWO～HW8)高熵合金。研究铸态和退火态合金的显微组织和拉伸性能。结果表明,HW2和HW4具有单一的FCC相。随着W含量和退火温度的增加,细小粒状μ相的面积分数增加且分散在FCC基体中。软FCC基体和硬μ相构成应变不相容的异质结构。随着W含量从0增加到8%(摩尔分数),屈服强度和抗拉强度分别从278和629 MPa提高到530和839 MPa,应变维持在33%。退火后的HW8表现出优异的屈服强度(810 MPa)和抗拉强度(1087 MPa)。屈服强度的提高归因于固溶、沉淀和背应力强化。异质结构中产生的背应力强化作用诱导高硬化行为,在提高抗拉强度和塑性方面发挥着主导作用。     

析出强化Fe53Mn15Ni15Cr10Al4Ti2C1高熵合金强韧化机制

以fcc结构高熵合金为基础合金,通过添加Al、Ti和C元素,设计了新型析出强化Fe₅₃Mn₁₅Ni₁₅Cr₁₀Al₄Ti₂C₁高熵合金。经过轧制后该合金含有纳米结构轧制条带(含有变形孪晶)和高密度位错结构。中温长时间热处理后该合金具有纳米结构非均匀组织,包括轧制条带、位错和大量的纳米析出相,表现出优异的强度-塑性匹配关系。该合金优异的力学性能是由于组织中与基体共格的L1₂型析出相起到了显著的析出强化作用,使该合金强度明显提高;另一方面,高密度位错得到有效回复,改善了合金的应变硬化能力。采用中温长时间热处理可获得强度-塑性匹配优异的非均匀组织析出强化高熵合金。     

激光熔化沉积成形新型多组元Ni3Al合金的组织与力学性能

设计了一种新型多组元Ni₃Al合金Ni₄₅Co₂₃Fe₉Al₁₁Ti₁₂,并采用激光熔化沉积(LMD)技术成功制备了合金。使用X射线衍射、扫描电镜、万能试验机等研究了沉积态合金的微观组织和室温力学性能。结果表明：LMD制备的Ni₄₅Co₂₃Fe₉Al₁₁Ti₁₂合金的晶粒为沿沉积方向外延生长的粗大柱状晶,晶粒由无侧向分枝的胞状枝晶组成,枝晶内部和枝晶间区域均由网状FCC基体和块状γ′相组成,且枝晶间区域的γ′相尺寸大于晶内。LMD成型的Ni₄₅Co₂₃Fe₉Al₁₁Ti₁₂合金具有良好的室温性能,其屈服强度达到879 MPa,抗拉强度为1160 MPa,断裂伸长率为9.5%,综合力学性能远优于同类合金,其屈服强度的显著提高可能与高密度γ′相...     

Ti对富Fe非等原子比高熵合金组织与性能的影响

在各元素成相作用和降低成本的基础上，利用机械球磨与放电等离子烧结的方法成功制备了一种富铁非等原子比Fe₄₅Cr₁₅Co₁₀Ni₃₀高熵合金。在该合金中通过降低Co和Ni的方式引入Ti元素，并研究了Ti的含量对合金力学性能的影响。结果表明：与Fe₄₅Cr₁₅Co₁₀Ni₃₀合金相比，含Ti的高熵合金出现了富Ti的BCC相；随着Ti含量的增加，FeCrCoNiTi高熵合金的微观组织发生了变化，富Ti的BCC相颗粒变得细小，相的形貌与分布也出现了变化，导致合金的硬度、屈服强度和抗拉强度先升高后降低，应变率逐渐降低，其中Fe₄₅Cr₁₅Co₆Ni₂₆Ti₈合金的综合性能最好，硬度为(404.2±6.3) HV0.3,屈服强度与抗压强度分别达到最高的(1036±12) MPa和(1883±10) MPa,应变率也维...     

富CoCr含量CoCrNiAlTi中熵合金的高温强韧化行为及微观机制

本工作研究了富CoCr含量的CoCrNi基中熵合金的高温力学性能及其变形机制。研究发现,经过热锻以及时效热处理,成分为Co_33.3Cr_30.6Ni_26.1Al₅Ti₅ (at%)中熵合金在600～800℃的温度范围内具有优异的瞬时拉伸性能。特别是,在700℃条件下出现反常屈服,屈服强度高达为944 MPa,拉伸塑性为16%,优于大多数镍基以及钴基高温合金。通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和三维原子探针(3D-APT)等手段,发现高体积分数的多主元γ′[(Ni,Co,Cr)₃(Al,Ti)]相的有序强化以及晶界处生成的多主元富(Co,Cr)面心立方相(fcc)结构相引起的晶界强化是该合金在高温条件下实现强韧化的主要因素。     

不完全再结晶Fe40Mn10Cr25Ni25高熵合金的室温及低温力学性能

采用冷轧和退火热处理工艺制备了不完全再结晶结构的Fe₄₀Mn₁₀Cr₂₅Ni₂₅高熵合金,分析了合金的室温(298 K)及低温(77 K)拉伸时的力学性能。结果表明,合金具有优良的室温及低温力学性能,合金在低温拉伸时强度和塑性均得到了提高,其室温强度和断后伸长率分别为880 MPa和18%,低温强度和断后伸长率分别为1360 MPa和36%。合金在室温变形以位错滑移为主,低温变形以位错滑移和孪生为主。室温拉伸时,粗晶晶粒先于细晶晶粒变形,导致试样内部产生了应变梯度,提高了合金的加工硬化率,使合金在室温下具有良好的强塑性。低温拉伸时,粗晶晶粒中形成了大量的变形孪晶,从而提高了合金的低温力学性能。     

(NiAl)63-xV20Cr17Bx共晶高熵合金的组织和性能

采用非自耗真空熔炼炉制备了一组非等摩尔比的高熵合金(NiAl)_63-xV₂₀Cr17B_x(x=0、0.2、0.4、0.6、0.8和1.0,摩尔比),通过XRD、EPMA、万能材料试验机等手段研究了B含量对合金微观组织和力学性能的影响。结果表明,(NiAl)₆₃V₂₀Cr₁₇合金为B2+BCC双相共晶结构,属于海藻状共晶枝晶,规则的片层共晶被不规则的片层共晶包围。随着B含量增加,(NiAl)_63-xV₂₀Cr₁₇Bx合金的微观结构由片层状共晶结构(x=0)转变为亚共晶结构(x>0.4),纳米沉淀物(含M₂B化合物)在初生相上析出。合金硬度先增加后减小,断裂强度和断裂应变持续增大。当x=0.8时,高熵合金具有良好的综合力学性能,其硬度(HV)为556,屈服强度为1 523 MPa,断裂强度为3 348 MPa,断裂应变为34.5%。     

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%。     

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.     

The crystal structure and magnetic properties of the Gd6Cr4Al43 compound

The crystal structure of intermetallic compound Gd₆Cr₄Al₄₃ has been investigated by means of X-ray diffraction data (Ho₆Mo₄Al₄₃ structure type, space group P6₃/mcm, Pearson symbol hP106, a = 10.9144(7) Å, c = 17.7361(13) Å).

SQUID magnetic measurements carried out for the title compound point to the existence of two antiferromagnetic phase transitions observed at T_N1 = 19.0(1) K and T_N2 = 6.8(1) K, respectively.     

Electrochemical investigation of the iron-containing and no iron-containing AB5-type negative electrodes

The electrochemical behaviour of LaNi_3.55Mn_0.4Al_0.3Co_0.75−xFe_x (x = 0, 0.15, 0.55, 0.75) intermetallic compounds has been studied and presented [C. Khaldi, H. Mathlouthi, J. Lamloumi, A. Percheron-Guégan, Int. J. Hydrogen Energy 29 (2004) 307–311; C. Khaldi, H. Mathlouthi, J. Lamloumi, A. Percheron-Guégan, J. Alloys Compd. 360 (2003) 266–271; C. Khaldi, H. Mathlouthi, J. Lamloumi, A. Percheron-Guégan, J. Alloys Compd. 384 (2004) 249–253]. It has been deduced that the LaNi_3.55Mn_0.4Al_0.3Co_0.4Fe_0.35 compound has interesting electrochemical properties. In this paper we present the electrochemical study of LaNi_3.55Mn_0.4Al_0.3Co_0.4Fe_0.35 compound properties compared with the parent LaNi_3.55Mn_0.4Al_0.3Co_0.75 compound. Several techniques, such as, the chronopotentiometry, the constant potential discharge (CPD), the cyclic voltammetry (CV) and the linear polarization (LP) were applied to characterize these electrochemical properties. The electrochemical discharge capacity of the LaNi_3.55Mn_0.4Al_0.3Co_0.75 alloy increases to reach 294 mAh g⁻¹ after few cycles only (five cycles). However, the activation of the LaNi_3.55Mn_0.4Al_0.3Co_0.4Fe_0.35 alloy takes more than 20 cycles to be achieved and the obtained maximum discharge capacity is 194 mAh g⁻¹. The hydrogen diffusion coefficient D_H was determined by constant potential discharge and cyclic voltammetry techniques. The obtained values of the LaNi_3.55Mn_0.4Al_0.3Co_0.75 and LaNi_3.55Mn_0.4Al_0.3Co_0.4Fe_0.35 compounds are 6.29 × 10⁻¹¹ and 7.62 × 10⁻¹¹, and 2 × 10⁻⁸ and 7.5 × 10⁻⁸ cm² s⁻¹ by CPD and CV techniques, respectively. The exchange current density values, determined by a linear polarization technique, are 44 and 27 mA g⁻¹, respectively, for LaNi_3.55Mn_0.4Al_0.3Co_0.75 and LaNi_3.55Mn_0.4Al_0.3Co_0.4Fe_0.35 alloys.     

Effect of alloy composition on enthalpy and entropy changes of hydride formation for stoichiometric and nonstoichiometric hydrogen storage alloys

Both enthalpy change ΔH° and entropy change ΔS° of hydride formation were evaluated from the measurement of pressure-composition isotherms (P-C-T curves) for hydrogen desorption in stoichiometric and nostoichiometric Mm (Ni₁₆Mn_11.4Al_0.3Co_0.7)₃ (Mm = misch metal, 0.88 x 1.12 values decreased with increasing x value, supporting that the low stability of the hydride causes the improved high-rate dischargeability of the Mm-poor Mm(Ni₁₆Mn_0.4Al_0.3Co_0.7)₁₁₂ alloy electrode.     

退火处理对CoCrFeNiB0.05Ti0.6高熵合金组织与力学性能的影响

采用机械合金化法制备CoCrFeNiB_0.05Ti_0.6高熵合金粉末,通过粉末冶金法制备了CoCrFeNiB_0.05Ti_0.6高熵合金。随后将烧结试样分别在450、650、850℃退火处理12 h。利用X射线衍射仪分析CoCrFeNiB_0.05Ti_0.6高熵合金退火前后的相结构;通过SEM和EDS分析CoCrFeNiB_0.05Ti_0.6高熵合金退火前后的微观组织形貌和元素分布情况;通过HXD-1000维氏硬度计和WDW-200万能试验测试机测量试样维氏硬度和压缩强度。结果表明,烧结态合金主要为FCC相伴随少量的HCP和Laves相;随着退火温度升高,BCC与硼化物等新相相继生成,Cr元素由浅灰色树枝晶向深灰色枝晶间的扩散程度逐渐增大,B元素与其它元素构成新的硼化物。烧结态合金为树枝晶与枝晶间组织,退火后枝晶间组织占比增大,树枝晶减少。CoCrFeNiB_0.05Ti_0.6...     

Deformation Behaviors of an Additive-Manufactured Ni32Co30Cr10Fe10Al18 Eutectic High Entropy Alloy at Ambient and Elevated Temperatures

Eutectic high-entropy alloys (EHEAs) that have superior formability are attractive for direct laser deposition technology. In this study, a regular-shaped bulk Ni₃₂Co₃₀Cr₁₀Fe₁₀Al₁₈ EHEA without apparent pores and micro-cracks was successfully fabricated by direct laser deposition. The as-deposited alloy showed a high tensile strength of 1.3 GPa with a ductility of 35% at ambient temperature and a tensile strength of 320 MPa at 760 °C. The deformation mechanisms of the as-deposited alloy at ambient and elevated temperatures were investigated by coupling the in-situ tensile test with a scanning electron microscope. It is revealed that the excellent combination of strength and ductility originated from the synergic effects of the FCC and B2 phases in eutectic lamellae. And the generation of cracks along phase boundaries restricted its high-temperature strength above 760 °C.     

Al25Nb20Ti30Zr25低密度高熵合金的组织和性能

通过Thermo-Calc软件计算、微观组织多尺度表征以及热模拟试验等研究了Al₂₅Nb₂₀Ti₃₀Zr₂₅合金的组织结构、高温组织稳定性和热加工性能。结果表明,Al₂₅Nb₂₀Ti₃₀Zr₂₅合金的铸锭组织主要由BCC基体相和Zr₅Al₃析出相组成,Zr₅Al₃相在BCC晶界连续析出,晶粒内部的Zr₅Al₃相呈块状分布,平均尺寸在750 nm左右;合金在750~1000 ℃保温24 h后,基体中的晶粒尺寸并未发生明显变化;随着温度的增加,Zr₅Al₃相含量小幅度降低,合金的高温组织稳定性较好。建立了合金的本构方程为$\dot{ε}$=4.5×10¹⁴×[sinh(0.0063σ_p)]^2.8exp(-419/RT),并绘制了合金的能量耗散系数图;在1050 ℃/1 s^-1变形条件下,能量耗散系数达到峰值0.69,在该变形条件下等温锻造出尺寸为$\phi$ 180 mm×20 mm完整无开裂的圆形块体材料。锻造消除了原始晶界处连续分布的Zr₅Al₃相,使其分解成短杆状均匀分布于合金基体中,BCC基体组织发生了动态回复和部分再结晶。