Phases,microstructures and properties of multi-component FeCoNi-based alloys

ABSTRACT

Disordered and ordered solid solution phases are identified in FeCoNi-based multi-component alloys. An ultimate strength of 2380?MPa was achieved in the dual face-centered cubic?+?body-centered cubic structural (FeCoNi)₆₀Al₁₅Cr₂₅ alloy, accompanied by a fracture strain of 38% and a hardness of 376.3?HV. After holding at 900°C for 100?h, oxidation resistance of the alloys follows by an increasing rank of (FeCoNi)₈₅Al₁₅?<?(FeCoNi)₇₅Cr₂₅?<?(FeCoNi)₆₀Al₁₅Cr₂₅. Moreover, the oxidation kinetic curves of the alloys follow a power-law dependence. (FeCoNi)₆₀Al₁₅Cr₂₅ alloy shows a good trade-off of mechanical properties and an excellent oxidation resistance at evaluated temperature, and can be a potential candidate for high temperature materials.     

Influence of Al content on thermal stability of nanocrystalline AlxCoCrFeNi high entropy alloys at low and intermediate temperatures

Thermal stability of mechanically alloyed nanocrystalline Al_xCoCrFeNi (x = 0, 0.3, 0.6, 1 mol) high entropy alloys (HEAs) has been investigated for the low and intermediate temperature range of 673–1073 K. Single phase FCC structure is observed in the as milled CoCrFeNi. A mixture of FCC and BCC phases is exhibited by × = 0.3, 0.6 and 1, alloys where the volume fraction of BCC increases with increasing Al content. Phase evolution in heat-treated Al_xCoCrFeNi HEAs proceeds via increasing BCC fraction at 673 K, followed by subsequent reduction at elevated temperatures. For each alloy, the major phase observed in as milled condition and it is retained even after prolonged exposure at the 1073 K. Al favors the formation of the BCC phase due to its high affinity to form ordered B2 structures with constituent elements Co, Fe and Ni. Thermal exposure of Al_xCoCrFeNi HEAs also leads to the formation of Cr₇C₃, owing to the higher negative free energy of carbide formation for Cr among other constituents. Transmission electron microscopy (TEM) investigations substantiated that nanostructure of milled powder is maintained even after the heat treatment. Grain growth factor for quinary HEAs is relatively lower than quaternary CoCrFeNi owing to their slower rates of diffusion.     

Tunability of the mechanical properties of (Fe50Mn27Ni10Cr13)100-xMox high-entropy alloys via secondary phase control

The single-phase face-centered cubic (fcc)-structured Fes0Mn27Ni10Cr1 3 high entropy alloy (HEA) exhibits good ductility but low strength,which presents a challenge.By Mo-alloying and thermomechanical treatments,we have designed the (Fes0Mn27Ni10Cr13)100-xMOx (x=0-6 at.％) alloy series with a wide range of mechanical properties.The careful control of secondary phases introduced in the cold-rolled and annealed (Fe50Mn27Ni10Cr13)Mo2 sample resulted in an enhanced tensile strength from 250MPa to 665 MPa,still having ～25 ％ ductility.TEM investigations of this alloy revealed the presence of deformation twins,dislocation cells,and ordered bcc nano-particles embedded in the ductile fcc matrix post-deformation.The observed deformation structures are an indication of successful cooperation between deformation twinning and precipitation strengthening in enhancing the tensile strength at maintained ductility compared to its cast counterpart.This work provides insight into the tunability of the mechanical properties of non-equiatomic HEAs via alloying and thermomechanical processing.     

Sb变质Mg-10Al合金的组织与力学性能

研究了不同Sb含量的Mg-10Al合金的微观组织及在室温和150℃高温下的力学性能。结果表明,加入适量的Sb,Mg-10Al合金中生成了弥散分布的针状Mg3Sb2相,α-Mg初晶显著细化,抑制了网状共晶组织的形成。当Sb含量为0.5%(质量分数)时,组织细化效果最佳。随着Sb含量的增加,室温及高温下合金的抗拉强度、屈服强度和伸长率先升高后降低,均在Sb含量为0.5%(质量分数)时获得最佳综合性能。Mg-10Al-0.5Sb合金在150℃的抗拉强度为180MPa、伸长率为19%,比Mg-10Al合金分别提高了30%和90%。此外,在150℃条件下,含Sb合金仍保持了与其在室温下相当的强度,而未添加Sb的Mg-10Al合金的强度则明显下降。     

微弧氧化处理对钛铌合金力学及摩擦磨损性能的影响

采用微弧氧化的方法于磷酸盐电解液中在二元β型TiNbx(x=5,10,15,20,25)合金表面制备了微弧氧化涂层.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)表征各合金表面微弧氧化涂层的物相组成和微观形貌.采用纳米压痕仪、球-盘摩擦磨损实验仪分析了微弧氧化处理对钛铌合金力学性能、耐磨性的影响.结果表明,通过微...     

Microstructure and corrosion behaviour of FeCoNiCuSnx high entropy alloys

Abstract

The FeCoNiCuSn_x alloys with different Sn contents are prepared, the microstructure and the corrosion behaviour of the alloys are investigated. When Sn content is lower than 0.09, FeCoNiCuSn_x alloys consist of a single FCC phase. While Sn content of the alloy is 0.09, a small quantity of BCC structure is present. The FeCoNiCuSn_x alloys have a wider passive region in the NaOH solution. FeCoNiCuSn_x alloys exhibit a better corrosion resistance in NaCl solution than 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.04 alloy is best among all the alloys. The corrosion resistance of FeCoNiCuSn_x alloys in NaOH solution is lower than that of 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.03 alloy is best among all FeCoNiCuSn_x alloys.     

Effect of minute element addition on the oxidation resistance of FeCoCrNiAl and FeCoCrNi2Al high entropy alloy

The effect of Ti_0.1 and Ti_0.1Si_0.1 addition on the high temperature isothermal oxidation behavior of dense FeCoCrNiAl and FeCoCrNi₂Al high entropy alloy (HEA) consolidated by vacuum hot pressing were investigated by X-ray diffraction, Scanning Electron Microscopy and Raman Spectroscopy. Mechanical properties such as hardness, Young’s modulus, and thermal properties such as differential scanning calorimetry (DSC) and coefficient of thermal expansion (CTE) were also investigated. The weight gain recorded after isothermal oxidation for 5,25,50 and 100 h at 1050 °C was found to be parabolic in nature. X-ray diffraction analysis (XRD), as well as Raman spectroscopy analysis of HEA’s oxidized at 1050 °C for 100 h, shows the formation of the Al₂O₃ phase. A homogeneous thin oxide scale without any discontinuity was observed throughout the cross-section. Ti and Si addition in 0.1 at. % improves mechanical properties, oxidation resistance, and reduces waviness of the oxide scale.     

Effects of Fe/Ni Ratio on Microstructure and Properties of FeNiCrAlNb High-Entropy Alloys

Herein, the effects of Fe/Ni ratio on the microstructure, mechanical properties, and corrosion resistance in a 3.5 wt% NaCl solution of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ are investigated systematically. It is found that the phases shifted from the FCC-dominated to the BCC-dominated with the molar ratio of the Fe/Ni increased. The strength of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ increases with the molar ratio of Fe/Ni further increased, while the plasticity decreases. The yield strength reaches 1,653 MPa at x = 45. The alloy exhibits the best corrosion resistance when x = 35 which is attributed to the dominant FCC phases in the dendritic region.     

Al元素对Al_xFeCrCoCuV高熵合金组织及摩擦性能的影响EI北大核心CSCD

采用非自耗电弧熔炼炉制备了Al_xFeCrCoCuV(x=0,0.5,1.0)多组元高熵合金。用XRD,SEM,EDS和DSC技术探究了合金的微观组织,并测试了其硬度及耐磨性能。研究表明:随着Al的加入,Al_(0.5)FeCrCoCuV合金和Al_(1.0)FeCrCoCuV合金由FeCrCoCuV合金单一的BCC相变为由枝晶BCC和晶间FCC共同组成的双相组织;Al_(1.0)FeCrCoCuV合金的硬度大于Al_(0.5)FeCrCoCuV合金。合金的摩擦磨损测试主要以黏着磨损为主,合金的耐磨性能与硬度成正比。3种合金的摩擦因数都是随着时间的增加而减小,主要原因是随着摩擦时间的增加,合金表面生成了一层氧化物提高了合金的耐磨性能。     

Phase stability,physical properties and strengthening mechanisms of concentrated solid solution alloys

We review recent research developments in a special class of multicomponent concentrated solid solution alloys (CSAs) – of which the recently discovered high entropy alloys (HEAs) are exemplars – that offer a new paradigm for the development of next generation structural materials. This review focuses on the role of inherent extreme chemical complexity on the phase stability, electronic, transport, and mechanical properties of this remarkable class of disordered solid solution alloys. Both experimental observations and theoretical models indicate that the phase stability of HEAs goes beyond the original conjecture that these alloys are stabilized by configurational/mixing entropy; rather, it results from competition between the homogeneously disordered phase and phase separation/intermetallic compound formation. Although the number of single-phase HEAs with equiatomic composition is limited, those that do exist often exhibit remarkable electronic, magnetic, transport, and mechanical properties. For the mechanical response, we discuss the solution strengthening mechanism which governs the strength and deformation behaviors of the CSAs, as well as the increasing evidence that low stacking fault energies (deformation twinning) plays an important role in the low temperature strength and ductility of CrMnFeCoNi related alloys. We also review the current understanding of the role of the number and type of alloy elements in determining the electronic, magnetic, and transport properties, in particular the dominant role of magnetic interactions in the properties of 3d-transition metal based alloys. Finally, we emphasize that, despite rapid progress in characterization and understanding of the phase stability and physical/mechanical responses of CSAs, there remain significant challenges to fully exploring the new paradigm that these alloys represent.     

1Cr17/9Cr18MoV多层复合钢板的组织与性能

采用包覆浇铸方法,经热锻、热轧后制备出各层钢板厚度较均匀分布的1Cr17/9Cr18MoV多层复合板。不同热处理工艺下的试验结果表明,采取加热温度950℃,保温0.5h后空冷的热处理工艺,可使复合板中9Cr18MoV钢获得较高的硬度,1Cr17钢获得较低的硬度,同时满足各层界面两侧附近的组织基本相同,硬度比较接近的要求。     

Kinetics of directed oxidation of Al-Mg alloys in the initial and final stages of synthesis of Al2O3/Al composites

In the directed oxidation of Al-Mg alloys, MgO forms in the initial stage. The mechanism of formation of MgO from the Al-Mg alloy in the initial stage of oxidation was studied. The variables studied were the total pressure in the reaction chamber and partial pressure of oxygen. The oxidation rate in the initial stage was proportional to both the oxygen partial pressure and oxygen diffusivity. These results suggest that MgO forms by reaction-enhanced vaporization of Mg from the alloy followed by oxidation of the Mg vapour in the gas phase. The end of the initial stage corresponds to the arrival of the oxygen front close to the melt surface, when spinel formation occurs.

The kinetics of formation of Al₂O₃ in the growth stage of directed oxidation of the Al-5wt.% Mg alloy was also investigated as a function of time, temperature and oxygen partial pressure. The growth rate decreased as a function of time, was practically independent of oxygen pressure and exhibited an activation energy of 361 kJ mol⁻¹. In the growth stage, the kinetics of oxidation is controlled by the rate of transport of oxygen through the alloy layer near the surface to the alumina-alloy interface.     

Additive manufacturing of metals: a brief review of the characteristic microstructures and properties of steels,Ti-6Al-4V and high-entropy alloys

Abstract

We present a brief review of the microstructures and mechanical properties of selected metallic alloys processed by additive manufacturing (AM). Three different alloys, covering a large range of technology readiness levels, are selected to illustrate particular microstructural features developed by AM and clarify the engineering paradigm relating process–microstructure–property. With Ti-6Al-4V the emphasis is placed on the formation of metallurgical defects and microstructures induced by AM and their role on mechanical properties. The effects of the large in-built dislocation density, surface roughness and build atmosphere on mechanical and damage properties are discussed using steels. The impact of rapid solidification inherent to AM on phase selection is highlighted for high-entropy alloys. Using property maps, published mechanical properties of additive manufactured alloys are graphically summarized and compared to conventionally processed counterparts.     

Microstructural evolution and mechanical properties of CoCrFeNiMnTix high-entropy alloys

This study was conducted to investigate the effect of titanium addition on the microstructure and properties of an equitaomic CoCrFeNiMn high-entropy alloy. Homogenized microstructures of CoCrFeNiMnTi_x (x = 0.1 and 0.3) alloys consist of face-centered cubic phase; however, addition of more titanium led to formation of a (chromium, titanium)-rich σ phase in CoCrFeNiMnTi_0.4 alloy. The average electron hole number calculations indicate the higher possibility of σ phase formation by adding more titanium. Furthermore, addition of an atom like titanium with a larger atomic radius in comparison with other elements can affect stability of face-centered cubic structure. Chromium and manganese has a destabilizing influence on the single face-centered cubic phase and manganese may reject chromium to facilitate the formation of a (chromium, titanium)-rich phase in alloys containing more than 5.5 at.% titanium (x>0.3). The mechanical properties revealed an improvement in strength without losing the ductility drastically by adding titanium up to 5.5 at.% (x = 0.3). Nevertheless, the strength remarkably increased and ductility significantly decreased in CoCrFeNiMnTi_0.4 alloy due to formation of brittle σ phase in the microstructure.     

Microstructure,phase formation and properties of rapid solidified Al–Fe–Cr–Ti alloys

Improvements in the mechanical strength of Al–Fe–Cr–Ti alloys have been demonstrated when non-equilibrium microstructures are developed. This paper investigated the effect of cooling rate and composition on the phase formation, microstructure and properties of new Al_96.6Fe_1.5Cr_1.7Ti_0.2 and Al_91.6Fe_4.9Cr_2.2Ti_1.3 (at.-%) alloys. Wedge-shaped samples produced by suction casting were characterised by optical, scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, energy dispersive X-ray spectroscopy and microhardness. The results showed that the morphology and size of the phases precedent of the flower-like phases change from small, spherical particles to large flower-like phases with decreasing the cooling rate. The presence of intermetallic phases Al₁₃Fe₄, Al₁₃Cr₂ and Al₃Ti in the Al_91.6Fe_4.9Cr_2.2Ti_1.3 alloy, resulted in a hardness 1.6 times higher compared to the Al_96.6Fe_1.5Cr_1.7Ti_0.2 alloy.     

Microstructure and mechanical properties of CoCrNi-Mo medium entropy alloys:Experiments and first-principle calculations

The effect of Mo additions on the microstructures and mechanical properties of CoCrNi alloys was investigated,meanwhile,ab initio calculations are performed to quantitatively evaluate the lattice distortion and stacking fault energy(SFE).The yield strength,ultimate tensile strength,and elongation of(CoCrNi)₉₇Mo₃alloy are 475 MPa,983 MPa and 69%,respectively.The yield strength is increased by~30%and high ductility is maintained,in comparison with CoCrNi alloy.Besides the nano-twins and dislocations,the higher density of stacking faults is induced during the tensile deformation for(CoCrNi)₉₇Mo₃alloy.Ab initio calculation results indicate the mean square atomic displacement(MSAD)and SFE value of(CoCrNi)₉₇Mo₃alloy is 42.6 pm²and-40.4 mJ/m²at 0 K,respectively.The relationship between mechanical properties and MSAD,SFE for various multiple principal element alloys is discussed.     

低温时效对Fe-22Al合金微观组织和力学性能的影响

利用金相显微镜、XRD、TEM和力学性能测试方法研究了低温时效对Fe-22Al合金的微观组织和力学性能的影响。结果表明,Fe-22Al合金经退火和固溶处理后的金相组织为粗大的等轴状晶粒,但固溶处理后晶粒尺寸有所减小。合金主要的相组成为α-Fe相以及具有B2结构的FeAl相,不存在DO3结构的Fe3Al相。存在明显的基体衍射斑点和(100)超点阵斑点意味着发生失稳有序化转变,并形成大量B2结构的有序相。暗场像结果表明存在大量Al原子的富集区和贫集区,即合金中发生了调幅分解转变。经过530℃时效处理后,合金的衍射斑点中同时存在DO3结构和B2结构的超点阵斑点。随时效的进行,逐渐发生B2→DO3相变,在B2结构的有序相内部形成大量细小的DO3相,并逐渐长大和粗化,最终形成粗大的海绵状结构。经过固溶和时效处理后,Fe-22Al合金的硬度和抗压强度分别为359HV、1610 MPa。     

13MnNiMoNbR与00Cr19Ni10异种钢焊接接头的组织与性能

首先将H309L焊丝堆焊在13MnNiMoNbR钢板坡口上,再将堆焊后的13MnNiMoNbR钢板与00Cr19Ni10钢板用H308L焊丝填充焊接,得到了13MnNiMoNbR与00Cr19Ni10异种钢焊接接头,并对接头的显微组织及硬度进行了分析。结果表明：13MnNiMoNbR钢板侧熔合线附近出现了粗大的铁素体组织,形成脱碳层,而H309L焊缝侧的奥氏体堆焊层熔合线附近出现了黑色的非常细小的碳化物析出层;由于碳化物的析出或是固溶碳,使H309L焊缝侧增碳层处的硬度明显升高。     

Thermal stability and thermal expansion behavior of FeCoCrNi2Al high entropy alloy

Present work reports the thermal stability and thermal expansion behavior of dual-phase FeCoCrNi₂Al HEA prepared by Mechanical Activated Synthesis and consolidated by hot pressing. The thermal stability of the phases present in FeCoCrNi₂Al HEA has been extensively studied using in-situ high-temperature X-ray diffraction (HT-XRD) in conjunction with dilatometry and differential scanning calorimetry (DSC). The DSC thermogram shows a single endothermic peak at 1430 °C (1703 K) which belongs to the melting point of the alloy. HT-XRD and dilatometry experiments were carried out from room temperature to 1000 °C (1273 K). HT-XRD study has shown that the room temperature FCC + BCC (face-centred cubic + body-centred cubic) phases remains stable up to 1000 °C (1273 K). Although the amount of BCC phase has increased above 800 °C (1073 K), no additional phase formation was observed in HT-XRD. The coefficient of thermal expansion (CTE) curve shows linear increment up to 1000 °C (1273 K) with a slight change in slope beyond 800 °C (1073 K). Theoretical CTE was computed using the lattice parameter of the FCC phase, obtained from HT-XRD, as a function of temperature and compared with experimental CTE. Third-order polynomial equation was fitted to the experimental CTE data and the constants were evaluated which can be used to predict the coefficient of thermal expansion of the alloy.     

微量Cu掺杂对TA10合金组织、力学性能与腐蚀行为的影响

研究了掺杂(0.5%~2.5%) Cu元素对TA10合金的微观组织、力学性能及腐蚀性能的影响,采用扫描电子显微镜(SEM)、金相显微镜(OM)研究合金的微观组织,并用XRD进行物相分析;采用电化学腐蚀、静态浸泡腐蚀试验研究合金的腐蚀性能。选出最佳合金成分,并通过原子力显微镜(AFM)对其做进一步分析。结果表明,随着Cu元素含量的增加,TA10合金基体组织被不断细化,添加2.5% Cu时,该合金的硬度值达到最大。Cu含量在1.0%~2.0%之间,合金的耐腐蚀性能较好。含Cu为0.5%的合金耐腐蚀性能优异。