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, ...     

热处理对耐磨合金铸铁组织和性能的影响

研究了奥氏体化温度及时间、回火温度及时间等热处理工艺参数对耐磨合金铸铁组织和性能的影响。结果表明,880℃保温40 min后油淬,200℃保温50 min回火后,合金的组织为回火马氏体、莱氏体和一些块状碳化物,洛氏硬度大于53 HRC,且冲击韧度和耐磨性能良好。     

等温热处理过程中铸态AZ91镁合金的微观组织演化

铸态AZ91镁合金加热至液固相温度区间内等温热处理后演变成半固态金属,对淬火组织形态分析的试验表明:在高固相体积分数条件下,网状分布的共晶组织首先熔化,二次枝晶臂消失或熔断脱落并重新沉淀在枝晶主干上,在Gibbs-Thomson效应下,发生Ostwald熟化,固相颗粒由枝晶逐渐演变成球形颗粒,并随着热处理时间的延长发生合并现象,而且热处理温度越高晶粒间合并现象越严重。同时在界面能降低的驱使下,晶粒内部包裹的液滴以两种方式形成:晶粒内富Al、Zn的质点经过熔化、扩散、合并、或者脱落的二次枝晶臂沉淀后搭桥生长形成。     

Effect of Ti Addition on the Microstructure and Property of FeAlCuCrNiMo_(0.6) High-Entropy Alloy

FeAlCuCrNiMo_(0.6)Tix(x=0.2,0.6,0.8) high-entropy alloys were fabricated with flux-cored wire and surfaced on low-carbon steel by gas metal arc welding.The effect of Ti addition on the microstructures and properties of FeAlCuCrNiMo_(0.6)Ti_x HEAs surfacing layer was systematically studied.The results show that FeAlCuCrNiMo_(0.6)Ti_x HEAs surfacing layer exhibits a majority of BCC solid solution based on Fe-Cr phase and a small amount of MC phase.Microhardness and wear tests results show that the addition of Ti can significantly improve the microhardness and wear resistance of the surfacing layer.The microhardness of surfacing layer can reach up to 642 HV_(0.5),which is about 2.8 times that of the substrate.Meanwhile,the wear mass loss is minimum.Electrochemical corrosion test results show that the addition of Ti can improve the corrosion resistance of surfacing layer,which is better than 304 stainless steel substrate.With the increase in Ti,the corrosion resistance increases first and then decreases.When the Ti content is 0.6,the self-corrosion current density of polarization curve is the smallest,the capacitive impedance radius of electrochemical impedance spectroscopy is the largest,and the corrosion resistance effect is the best.     

均匀化热处理对牙科烤瓷无钯高金合金组织性能的影响

研究了均匀化热处理对一种无钯牙科高金烤瓷合金组织性能的影响,对其进行了950℃保温30min的均匀化处理,然后快速在冰水混合物中淬火,并对之做了一系列测试分析.实验结果显示合金在均匀化热处理后,组织显著均匀化,硬度显著降低.淬火后的合金仍为α1和α2两相组织,但富铂的α2相颗粒的量比铸态组织明显减少,颗粒的尺寸也有所减小,SEM下观察有很强的立体感.作者认为合金高温淬火后仍为两相组织,而非单一均匀相,主要与热处理温度和材料的固态相变温度相距较近有关.     

Microstructure,Mechanical and Corrosion Properties of AlCoCrFeNi High-Entropy Alloy Prepared by Spark Plasma Sintering

AlCoCrFeNi is one of the most widely studied alloy systems in the high-entropy alloy(HEA) area due to the interesting microstructure and mechanical properties.In this study,the AlCoCrFeNi alloy was prepared using spark plasma sintering(SPS) with pre-alloy powders obtained through gas atomization.Then,the sintered samples were annealed at 700,800 and900℃,and the effect of annealing temperature on the microstructure,mechanical and corrosion properties was studied.The results show that phase formation takes place during annealing process with the new phase(σ) and some nano scale BCC precipitates formation.The size and quantity of the nanoscale precipitates increase with increasing annealing temperature.The twin is also observed after annealing at 900℃.The annealing temperature has an obvious effect on the mechanical properties and corrosion resistance of the spark plasma sintered AlCoCrFeNi HEA.When the annealing temperature is 700℃,the hardness,yield strength and fracture strength reach the maximum with the value of 545 HV,1430 MPa and 2230 MPa,respectively.The compressive ratio reaches the maximum of 17.2%,with the annealing temperature increasing to 800℃.The corrosion resistance of the samples decreases with increasing the annealing temperature.     

等温处理对Al-7Si-4Cu合金组织和硬度的影响

研究了铸造Al-7Si-4Cu合金在半固态等温处理过程中组织、性能的变化。结果表明,通过调整等温处理时间、温度不仅可以改善铸造铝硅铜合金的组织,而且提高了合金的力学性能。在一定的冷却速率下,适当延长等温处理时间、提高等温处理温度有利于硅相的圆整化、细化。在半固态温度下进行保温,当保温时间为5min时,可获得弥散相,保温温度高,弥散相多;延长保温时间至10min,未发现弥散相析出,而硅相圆整、细小,分布均匀,弥散相多,合金硬度就高。     

热处理对Zn-11%Al-8%Cu-Mg合金组织性能的影响

研究了热处理对Zn-11%Al-8%Cu-Mg合金组织性能的影响。结果表明,热处理后锌合金晶粒细化,组织分布更加均匀,共晶组织的形貌变得圆整;热处理后的抗拉强度和伸长率增加,但布氏硬度有所下降,综合性能得到改善。     

Effect of Heat Treatment on the Microstructure and Mechanical Properties of the Modified 718 Alloy

M718 alloy with an extra high Mo content of 7.50 wt% which reduced Nb addition and increased Al and Ti additions within the composition specifications of 718 alloy has been designed to increase the service temperature of 718 alloy. And the effect of the heat treatment on the microstructure and mechanical properties of M718 alloy has been investigated in this study. The results showed that Laves phase precipitated on the grain boundaries of M718 alloy instead of d-Ni_3 Nb phase in718 alloy, and y'and y'phases precipitated in the matrix of M718 alloy as that in 718 alloy. Increasing the solution temperature from 960 to 1050 ℃ noticeably reduced the intergranular precipitation of Laves phase. The precipitation of Laves phase was appropriate at 1020 ℃ for improving the grain boundary cohesion. Increasing the two-stage aging temperatures markedly increased the sizes of y' andy'phases. As a result, the strength of M718 alloy increased.     

固溶处理对触变成形ZA27合金微观组织和硬度的影响

研究了固溶处理对经5年自然时效的触变成形ZA27合金硬度的影响,并应用扫描电镜(SEM)和XRD对金相显微组织做了进一步的研究。结果表明:在360℃下固溶处理24h后,合金的微观组织由近球状的初生粒子(黑色)和晶间的二次凝固组织转变为单一的β相。固溶处理对合金硬度的影响则是原始强化相η相的溶解与稳定的β相不断析出的综合结果。固溶处理开始几小时后,由于原始强化相的溶解,材料的硬度下降,而后随着固溶时间的增加,强化相的不断析出,硬度不断提高,当到一定的程度,组织出现了过饱和的亚稳态,硬度又开始降低。     

Effects of Homogenized Treatment on Microstructure and Mechanical Properties of AlCoCrFeNi_(2.2) Near-Eutectic High-Entropy Alloy

A 4 kg AlCoCrFeNi_(2.2) near-eutectic high-entropy alloy ingot was prepared by vacuum medium frequency induction melting. The effects of homogenized treatment on microstructure and mechanical properties of AlCoCrFeNi_(2.2) were studied. The results showed that all the alloys consisted of the primary FCC phases and eutectic FCC/B2 phases. After homogenized treatment, lots of precipitated phases appeared in the primary phase. The hardness of the as-cast alloy was HV296. The hardness values of samples were decreased and were around HV250 after homogenized treatment. The tensile fracture strength of the as-cast alloy reached 900 MPa, while the elongation was 18%. After homogenized treatment at 900 ℃, the alloy showed the most excellent mechanical properties with the fracture strength 880 MPa and the elongation was 29%, respectively. All the alloys displayed a mixture fracture mechanism, including ductile fracture in primary FCC phases and eutectic FCC phases, and brittle quasi-cleavage fracture in eutectic B2 phases. Through a simple heat treatment method, the strength of the alloy was not reduced but the plasticity was greatly enhanced, which was more conducive to the industrial application prospects.     

Microstructure and properties of Al0.3CrFe1.5MnNi0.5Ti x and Al0.3CrFe1.5MnNi0.5Si x high-entropy alloys

In this article, the microstructure, hardness, and corrosion resistance of the Al0.3CrFe1.5MnNi0.5Tixand Al0.3CrFe1.5MnNi0.5Six(x = 0, 0.2, 0.5, 1.0) high-entropy alloys were investigated via X-ray diffraction(XRD)scanning electron microscopy(SEM), digital display Vickers hardness tester, and electrochemical technique These alloys are mainly composed of BCC solid-solution structure. When adding high content of Ti or Si elemen(x C 0.5), some intermetallic compounds are found in the microstructure, which makes the alloys have a high hardness, high brittleness, and easy cracking. While the alloys with low content of Ti or Si(x = 0.2) have a hardness of HV 420–HV 430, and its hardness increases about 14 %compared with that of Al0.3CrFe1.5MnNi0.5. Electrochemical results in 3.5 % NaCl solution show that the alloying elements Ti and Si have a negative influence on the corrosion resistance of the Al0.3CrFe1.5MnNi0.5alloys.     

热处理对Al0.5CoCrFeNiB-0.2高熵合金组织结构及力学性能的影响

采用真空电弧炉制备Al0.5CoCrFeNiB0.2高熵合金,采用X射线衍射仪、金相显微镜、扫描电镜等方法研究铸态合金的组织结构及其热处理的影响,采用显微硬度计和拉伸试验测定合金热处理前后的力学性能。结果表明:Al0.5CoCrFeNiB0.2铸态合金仅由简单的体心立方结构和两个面心立方结构三相组成。合金铸态组织由树枝状初生α1相、粒状α2相和共晶组织(α1相和层片状β相)组成。退火和淬火热处理并未改变Al0.5CoCrFeNiB0.2合金的相结构。但随着热处理温度的提高,初生α1相由共晶组织β相回溶而长大的趋势更加明显。退火和淬火热处理均可强化合金。其中,经800℃×10 h退火后,合金室温抗拉强度由铸态的850.14 MPa提高到1 232 MPa;经1 000℃×10 h淬火后,合金塑性及强度均优于铸态合金,尤其是塑性显著提高。     

时效处理对Ti55531钛合金微观组织演变规律及力学性能的影响

在INSTRON-5948R微型材料试验机上开展了近β型钛合金Ti55531经800℃/2 h固溶+580～640℃/6～10 h时效热处理后的力学性能试验,获得了不同时效工艺下Ti55531合金的力学性能及强塑积。研究了时效处理对合金微观组织演变规律及合金在拉伸变形时的断裂机制。结果表明：次生片层αs相对时效参数变化比初生α相更敏感。次生片层αs相厚度与时效温度或时效时间呈线性正相关。与时效时间对比可知,次生片层αs相粗化速率对时效温度敏感性较弱,且其随时效温度和时效时间粗化速率分别约为1 nm/℃和8 nm/h。合金经固溶时效后,其力学性能显著提升,且合金在800℃/2 h固溶+640℃/8 h时效后达到最佳的综合力学性能,此时抗拉强度为1144 MPa,延伸率为8.16%,且强塑积超过9.3 GPa·%。合金经固溶时效热处理后拉伸断裂形式为韧脆混合型断裂,且以韧性断裂为主,包括晶间开裂和微孔合并。     

Ti6242合金组织演化的精细分析

以等轴组织Ti6242合金为研究对象,采用光学显微镜与扫描电镜2种组织观察手段,结合图像处理软件的自动处理与统计学方法,分析了不同热处理制度下合金组织的精细特征与演变规律。建立了采用体积分数Vα、尺寸Dα、分布密度ρα和聚集程度Eα4个参量来精确定量描述等轴初生α相特征及演化的方式,发现V_α、D_α、ρ_α和E_α均随固溶温度的升高而减小,V_α和ρ_α分别满足线性和抛物线规律;V_α的减小速度随温度升高而增加,随时间的延长而降低。随V_α减小,β相中Al元素含量增加,Sn、Zr和Mo三元素含量均降低;4种合金元素在α与β两相中的含量差异变小。850与800℃下,β相的[Mo]_(eq)分别落入α+β型和亚稳β型钛合金对应的[Mo]_(eq)区间,水淬后β相分别发生马氏体转变和保留亚稳态。     

Phase Selection and Microhardness of Directionally Solidified AlCoCrFeNi2.1 Eutectic High-Entropy Alloy

In the present work, the solidi?cation behaviors and microhardness of directionally solidi?ed AlCoCrFeNi_2.1 eutectic highentropy alloy (EHEA) obtained at different growth velocities are investigated. The microstructure of the as-cast AlCoCrFeNi _2.1 EHEA is composed of bulky dendrites (NiAl phase) and lamellar eutectic structures, indicating that the actual composition of the alloy slightly deviates from the eutectic point. However, it is interesting to observe that the full...     

直流电流作用下AZ91D镁合金半固态等温处理过程中的组织演变

考察了直流电流密度、等温温度及等温时间对AZ91D镁合金半固态组织的影响,对电流影响组织演变的机理进行了探讨．实验结果表明：当等温温度和等温时间一定时,随着电流密度的增加,初生相变得圆整,初生相的尺寸有所减小．但电流密度过高时,初生相尺寸有所增加．直流电流可以加速半固态等温处理的组织演化过程,明显改善枝晶球化效果．直流电流增加扩散激活能,增大溶质原子的扩散系数,促进溶质原子的扩散,从而加速半固态等温过程的组织演化;直流电流作用下的电迁移效应、Joule热效应和Peltier效应都将促进枝晶的熔断和球化．     

Selective Laser Melting of Al-7Si-0.5 Mg-0.5Cu: Effect of Heat Treatment on Microstructure Evolution,Mechanical Properties and Wear Resistance

Al-7Si-0.5 Mg-0.5Cu alloy specimens have been fabricated by selective laser melting (SLM). In this study, the effects of solution treatment, quenching, and artificial aging on the microstructural evolution, as well as mechanical and wear properties, have been investigated. The as-prepared samples show a heterogeneous cellular microstructure with two different cell sizes composed of α-Al and Si phases. After solution-treated and quenched (SQ) heat treatment, the cellular microstructure disappears, and coarse and lumpy Si phase precipitates and a rectangular Cu-rich phase were observed. Subsequent aging after solution-treated and quenched (SQA) heat treatment causes the formation of nanosized Cu-rich precipitates. The as-prepared SLMs sample has good mechanical properties and wear resistance (compressive yield strength: 215 ± 6 MPa and wear rate 2 × 10^-13 m³/m). The SQ samples with lumpy Si particles have the lowest strength of 167 ± 13 MPa and the highest wear rate of 6.18 × 10^-13 m³/m. The formation of nanosized Cu-rich precipitates in the SQA samples leads to the highest compressive yield strength of 233 ± 6 MPa and a good wear rate of 5.06 × 10^-13 m³/m.     

深冷处理过程中Inconel 617合金的微观组织演变（英文）

研究了Inconel 617合金在不同深冷处理时间和次数条件下微观组织的演变规律。结果表明,深冷处理对Inconel 617合金的微观组织结构有很大的影响,随着深冷处理时间的延长,晶粒尺寸减小,但是随着深冷处理次数的增加,晶粒尺寸又增大,并且细化晶粒的晶界处具有高的应力。晶格常数与晶粒尺寸的变化相反。深冷处理试样析出了MC、M₆C、M₂₃C₆的简单和复杂碳化物,导致了位错的塞积。深冷处理24 h后试样的几何必须位错(GND)密度增大,当24 h循环处理2次后,GND密度显著降低。此外,深冷处理导致Inconel 617合金的旋转立方织构和旋转铜织构转变为黄铜织构、P织构、高斯织构。     

Microstructure Evolution and Phase Transformation of Ti–6.5Al–2Zr–Mo–V Alloy During Thermohydrogen Treatment

Thermohydrogen treatment(THT) is an effective way to refine microstructure and improve the mechanical properties of the titanium alloys.In the current work,as-cast Ti–6.5Al–2Zr–Mo–V alloy was hydrogenated with different hydrogen contents and processed solution aging.Accordingly,the microstructure evolution and phase transformation were analyzed.Results show that during solution aging,eutectoid decomposition occurs and the product is a mixture of coarse primary a,fine eutectoid product and undecomposed bH.The size of primary a is closely dependent on the hydrogen content,and large primary a can be obtained at medium hydrogen content.Further,the influence of hydrogen content on the growth of primary a phase was revealed.The primary a is much fine,and the eutectoid product is relatively homogeneous with 0.984 wt% H.After THT,the ultimate strength is beyond 1,100 MPa that has increased by 23.15% compared with that in as-cast state.