Mg-Cu-Zn-Y快速凝固组织的演化及压缩性能研究

采用快速凝固法制备了Mg65+χ(Cu0.66 Y0.34)30-χ Zn5(χ=0、5、10、15)合金样品,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)对制得样品的结构和组织进行了表征.结果表明,χ=0的S-1样品主要由基体相、尺寸较小的块状Mg2Cu相和少量的MgZnY相组成,随着Mg含量的增加,样品中还会出现片状的Mg相及颗粒状的MgZnY相,同时Mg相会有所增加,且其尺寸也增大.通过测试合金的压缩应力应变曲线,发现χ=10的S-3样品具有高的强度和良好的塑性,其最大压缩强度达到1098MPa,断裂时的应变值高达14%.     

电子束熔炼Nb-Si系多元合金的组织和性能

采用电子束熔炼对Nb-Ti-Si-Cr-Al-Hf多元合金进行重熔,研究合金锭成分与组织的均匀性以及合金的硬度、室温断裂韧性、高温抗压性能.结果表明:电子束熔炼易导致合金元素的挥发损失,使得合金锭的成分不均匀;高的冷却速度有助于细小、均匀的等轴组织形成,其中硅化物相的显微硬度HV约为1100,是Nb固溶体相的3倍左右;电子束熔炼Nb-Si系多元合金的室温断裂韧性(KQ)约为10.3MPa·m1/2;在1250℃的抗压强度约为426.3MPa,且具有一定的高温塑性.     

铌硅化物基超高温合金电弧熔炼态组织和成分分布

采用真空非自耗电弧熔炼后再真空自耗电弧熔炼的方法制备了Nb-Ti-Si-Cr-Al-Hf-Mo-B-Y超高温合金的母合金锭,分析了合金锭不同位置的组织形貌、相组成和成分分布特点.结果表明:母合金锭主要由Nbss, (Nb,X)5Si3和(Nb,X)3Si三相组成.母合金锭组织主要由初生Nbss枝晶,花瓣状Nbss+(Nb,X)5Si3共晶和块状(Nb,X)3Si组成;但在母合金锭底部和顶部的中心部位组织却由分布均匀的Nbss+(Nb,X)5Si3共晶组成,没有出现初生树枝状Nbss和块状(Nb,X)3Si.母合金锭中的成分分布特点为Si由锭边缘向中央逐渐升高,Ti由边缘向中央逐渐递减.     

电弧熔炼Nb-Ti-Si-Cr-Hf-Al-B-Y超高温合金母合金锭的组织形成和成分分布特点

采用真空非自耗电弧熔炼然后再真空自耗电弧熔炼的方法制备了Nb-Ti-Si-Cr-Hf-Al-B-Y超高温合金的母合金锭,分析了其在不同位置的组织组成及成分分布特点.发现母合金锭的组织主要由Nbss与(Nb,X)5Si2两相组成.在母合金锭的边缘部位,组织主要由(Nbss (Nb,X)5Si3)共晶团组成,此外还有少量的Nbss枝晶;但在母合金锭的中央部位,组织由初生(Nb,X)5Si3块或板条以及(Nbss (Nb,X)5Si3)共晶团组成.母合金锭中的成分分布特点为Si含量由锭边缘向中央逐渐升高,而由锭下部到上部逐渐降低;Ti含量的变化则为由锭边缘向中央,由锭下部到上部逐渐减少.     

钽元素对Co-8.8Al-9.8W合金微观组织和力学性能的影响规律

为了研究合金化Ta(钽)元素对Co-8.8Al-9.8W高温合金微观组织和力学性能的影响,通过对Co-8.8Al-9.8W-xTa(x=0,1,2,4,6,原子分数,％,下同)合金微观组织和室温压缩性能的研究发现:铸态合金组织由γ基体相和衬度较亮的晶间相组成,枝晶间析出的白色衬度晶间相随着Ta含量的增加逐渐增多,并与γ基体相呈现出典型的共晶组织.经过1300℃/4 h的固溶处理和900℃/50 h的时效热处理,γ基体上析出均匀细小的γ'强化相,并且随Ta元素含量的增加,团簇状二次相(μ相、x相和β相)逐渐增多.Co-8.8Al-9.8W-xTa(x=0,1,2,4,6)合金在铸态和热处理状态下的显微硬度均随着Ta含量的增加而增加,其中,6Ta合金在铸态和热处理状态下均表现出最大的显微硬度,分别为567 HV和625 HV.室温压缩下,除1Ta合金外,其他合金的屈服强度σ0.2随着Ta元素含量的增加而逐渐增大,6Ta合金表现出1259 MPa的最大屈服强度;合金的极限抗压强度随着Ta元素含量的增加而先增大后减小,且在4Ta合金中表现出2522 MPa的最大抗压强度;所有合金中2Ta合金表现出22.95％的最大塑性变形能力.     

真空熔炼多组元Cu_xAlFeNiCrTi高熵合金的显微组织和性能

多组元高熵合金是一种具有五种以上组元的新型合金。通过真空电弧熔炼炉熔铸得到了不同铜含量的高熵合金Cu_xAlFeNiCrTi(x=1和0.5),再通过光学显微镜、X射线衍射仪、扫描电镜、透射电镜以及显微硬度计分析了高熵合金的显微组织、结构、硬度和耐腐蚀性能等。结果表明:高熵合金具有简单的相结构,合金硬度在800 HV以上,耐碱腐蚀性能优于耐酸腐蚀性能;随着铜元素含量的减少,合金结构由体心立方+面心立方结构变为体心立方结构,合金硬度增加,耐腐蚀性能提高。     

电子束熔炼Inconel 740合金不同热处理状态下的组织演变与显微硬度

利用电子束熔炼技术制备Inconel 740合金,研究热处理状态下合金的组织演变过程与显微硬度的分布情况,分析热处理过程中合金相析出规律与相分布特点。结果表明:合金宏观组织良好,夹杂物含量较少,晶粒尺寸在2mm左右。标准热处理后的组织主要为奥氏体,并有大量孪晶,晶界上碳化物M23C6呈连续分布,同时也有G相和η相析出。晶内析出大量球形、尺寸大小约为30nm的强化相γ′。电子束熔炼制备的Inconel 740合金在标准热处理状态下的显微硬度明显高于传统方法制备的同种合金,约高120HV0.1。     

微量碳对IC6合金真空熔炼过程及其对合金微观组织和力学性能的影响

为了有效解决ＩＣ６合金真空熔炼过程中的氧化膜问题,进行了加入微量碳的试验,在成分为Ｎｉ－８．９Ａｌ－１４．０Ｍｏ０．０２５Ｂ（ｗｔ％）的母合金中,分别添加了五种不同量的碳（０,０．０３,０．０６,０．１２,０．１８ｗｔ％）,观察了真空熔炼过程中的氧化膜变化情况,并采用招揽世镜分析了合金的微观组织。测定了合金室温拉伸性能。综合考虑加入不同碳量的微观组织、力学性能以及碳对氧化膜的作用程度 ,确定了最佳     

铝合金表面Ti-Al双丝超音速电弧喷涂涂层的组织与性能研究

利用SAS－1型超音速电弧喷涂设备和钛、铝丝在适当的工艺条件下，在LY12铝合金表面制成了钛铝合金复合涂层。并利用金相显微镜、X射线衍射仪、扫描电镜、X射线能谱仪、电子探针等，对涂层的成分、相结构、显微结构、孔隙率及其结合强度、显微硬度和耐磨性进行了研究。结果表明，利用超音速电弧喷涂设备，可以在铝基表面形成低孔隙率小于2.8%，结合强度为29MPa，显微硬度HV0.2为631和干滑动磨损体积仅为LY12基体1／7的TiAl合金涂层。显微组织观察发现，涂层与基体间有冶金结合的迹象，组织结构分析表明，涂层由TiN（TiO)，Al,Ti,TiAl,Ti3Al等相组成。涂层的磨损机制可能以化合物等硬质相的剥落引起的磨粒磨损和氧化磨损为主。     

Cr对FeCoNiAlCrx高熵合金组织与力学性能的影响

采用真空电弧熔炼法制备FeCoNiAlCr_x(x=0,0.2,0.4,0.6,0.8,原子比,下同)高熵合金铸锭,探究Cr含量对该合金微观结构、组织及力学性能的影响。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)对合金相结构、微观组织及成分进行分析表征;采用万能试验机对合金压缩性能进行测试。结果表明：随着Cr含量的增加,合金的微观结构由单相BCC结构转变为BCC+FCC混合结构;合金微观组织由等轴晶逐步转变为树枝晶,并且合金晶粒尺寸发生了明显细化。本实验制备的五种合金都具有较好的力学性能,合金的抗压强度随着Cr含量的增加大幅度增强,当x=0时合金抗压强度和塑性应变最低,分别为1500 MPa和13.56%;当x=0.8时,合金抗压强度和塑性应变达到最大,分别为2460 MPa和30.09%;合金抗压强度的增幅达64%。这表明Cr添加对FeCoNiAlCr_x高熵合金的组织细化、抗压强度和塑性的提升具有重要作用。     

Microstructure,biodegradation, antibacterial and mechanical properties of ZK60-Cu alloys prepared by selective laser melting technique

Magnesium (Mg) alloys are receiving increasing attention for body implants owing to their good biocompatibility and biodegradability. However, they often suffer from bacterial infections on account of their insufficient antibacterial ability. In this study, ZK60-xCu (x?=?0, 0.2, 0.4, 0.6 and 0.8?wt%) alloys were prepared by selective laser melting (SLM) with alloying copper (Cu) to enhance their antibacterial ability. Results showed that ZK60-Cu alloys exhibited strong antibacterial ability due to combination of release of Cu ions and alkaline environment which could kill bacteria by destroying cellular membrane structure, denaturing enzymes and inhibiting deoxyribonucleic acid (DNA) replication. In addition, their compressive strength increased due to grain refinement and uniformly dispersing of short-bar shaped MgZnCu phases. Moreover, ZK60-Cu alloys also exhibited good cytocompatibility. In summary, ZK60-Cu alloys with antibacterial ability may be promising implants for biomedical applications.     

Microstructure and mechanical properties of Al-Si-Ni-Ce alloys prepared by gas-atomization spark plasma sintering and hot-extrusion

Al-Si-Ni-Ce alloys with the composition of Al_78.5Si₁₉Ni₂Ce_0.5, Al₇₆Si₁₉Ni₄Ce₁ and Al₇₃Si₁₉Ni₇Ce₁ were atomized and then sintered by using spark plasma method. The microstructure of the as-atomized powders, sintered and hot-extruded samples was analyzed. The influences of granularity and sintering parameters including time and temperature on the density of sintered alloy were also discussed. It is shown that the atomized powders are composed of Si, Al₁₁Ce₃, Al₃Ni and alpha Al. Tiny Al₃Ni particles precipitate from supersaturated matrix near the powder boundaries during SPS. Hot-extrusion process leads to the layer structure and more homogeneous distribution of precipitates. These alloys exhibit high comprehensive mechanical properties with combination of high Vicker's micro-hardness, moderate tensile properties and elongation, which provide a novel kind of promising engineering materials.     

Nano-SiC reinforced Zn biocomposites prepared via laser melting:Microstructure,mechanical properties and biodegradability

Zn has been regarded as new kind of potential implant biomaterials due to the desirable biodegradability and good biocompatibility,but the low strength and ductility limit its application in bone repairs.In the present study,nano-SiC was incorporated into Zn matrix via laser melting,aiming to improve the mechanical performance.The microstructure analysis showed that nano-SiC distributed along Zn grain boundaries.During the laser rapid solidification,nano-SiC particles acted as the sites for heterogeneous nucleation,which resulted in the reduction of Zn grain size from 250 μm to 15 μm with 2 wt%SiC(Zn-2 SiC).Meanwhile,nano-SiC acted as a reinforcer by virtue of Orowan strengthening and dispersion strengthening.As a consequence,the nanocomposites showed maximal compressive yield strength(121.8±5.3 MPa) and high microhardness(72.24±3.01 HV),which were increased by 441% and 78%,respectively,compared with pure Zn.Moreover,fracture analysis indicated a more ductile fracture of the nanocomposites after the incorporation of nano-SiC In addition,the nanocomposites presented favorable biocompatibility and accelerated degradation caused by intergranular corrosion.These findings suggested that the nano-SiC reinforced Zn biocomposites may be the potential candidates for orthopedic implants.     

Microstructural refinement of 6061 and 5052 aluminium alloys by arc oscillation

The mechanism of the microstructure refinement of metals and alloys (5052 and 6061) by arc oscillating was studied and discussed via the grain size of regular welds and those welded at different oscillation frequencies. In 5052 alloy, fine columnar crystals appeared near the ‘internal fusion line’ during the oscillating arc welding and the grains have been significantly refined by oscillating arc with low and high frequency. However, the grain refinement of 6061 Al alloy was limited during arc oscillating welding due to the different crystal growth pattern at the fusion line and material properties. It is not caused by changing of the grain refinement mechanism but by the difference in the material properties.     

Microstructure and mechanical properties of Al-12Si and Al-3.5Cu-1.5Mg-1Si bimetal fabricated by selective laser melting

An Al-12 Si/Al-3.5 Cu-1.5 Mg-1 Si bimetal with a good interface was successfully produced by selective laser melting(SLM).The SLM bimetal exhibits four successive zones along the building direction:an Al-12 Si zone,an interfacial zone,a texture-strengthening zone and an Al-Cu-Mg-Si zone.The interfacial zone(<0.2 mm thick)displays an increasing size of the cells composed of eutectic Al-Si and a discontinuous cellular microstructure,resulting in the lowest hardness of the four zones.The texturestrengthening zone(around 0.3 mm thick)shows a remarkable variation of the hardness and<001>fiber texture.Electron backscatter diffraction analysis shows that the grains grow gradually from the interfacial zone to the Al-Cu-Mg-Si zone along the building direction.Additionally,a strong<001>fiber texture develops at the Al-Cu-Mg-Si side of the interfacial zone and disappears gradually along the building direction.The bimetal exhibits a room temperature yield strength of 267±10 MPa and an ultimate tensile strength of 369±15 MPa with elongation of 2.6±0.1%,revealing the potential of selective laser melting in manufacturing dissimilar materials.     

电弧堆焊铁基非晶/纳米晶复合涂层的组织及性能研究

以铁基非晶合金Fe41Co7Cr15Mo14C15B6Y2作为焊芯制备低氢型非晶堆焊焊条,利用手工电弧堆焊,调控堆焊工艺参数,在Q235钢上制备两种不同非晶/纳米晶组分的复合堆焊层。利用XRD/SEM/TEM探索不同堆焊工艺下的结构组织演变及非晶/纳米晶的组成比例变化,研究了不同比例非晶/纳米晶复合堆焊层的晶化特征、硬度和耐磨性变化。实验结果表明,堆焊层为铁基非晶/纳米晶复合涂层,与基体达到了良好的冶金结合;涂层中非晶相含量最高可达47.44%,纳米晶粒尺寸为10~48 nm,堆焊层的最高硬度达1 226HV1,其耐磨性可达Q235钢的8倍;两组堆焊层的晶化激活能分别为Ex(150 A)=107.476 kJ/mol,Ex(160A)=58.104 kJ/mol;随着堆焊热输入的增加,堆焊层中非晶相的含量降低,纳米晶粒尺寸增大,堆焊层的晶化温度、热稳定性、硬度和耐磨性有所降低。     

挤压Zn-Cu-Ti合金的组织及其力学性能

采用Zn-Ti中间合金等制备了不同铜含量的锌合金,370℃/4h均匀化后在300℃对合金进行了热挤压加工。通过X射线衍射分析、扫描电镜分析和能谱分析以及力学性能测试,研究了合金的微观组织和力学性能之间的关系。结果表明,Zn-Cu-Ti合金主要由锌的固溶体η相,TiZn15相和CuZn4相组成,Ti元素的加入细化了合金的显微组织,提高了合金的力学性能;热挤压过程中,合金发生动态再结晶和局部再结晶晶粒长大现象,TiZn15相和CuZn4相被破碎后沿挤压方向分布于晶界处,有助于阻碍再结晶晶粒的长大;Cu含量在0.5%~3.0%范围内,随着含铜量的增加,Zn-Cu-Ti合金的强度和硬度增大,当Cu含量超过2.0%时伸长率有下降趋势;由于挤压过程中发生了动态再结晶在一定程度上抵消了加工引起的硬化,合金挤压态硬度较铸态硬度提高不大。     

Microstructure and mechanical properties of hot rolled TiNbSn alloys

Titanium alloys with lower elastic modulus and free from toxic elements such as Al and V have been studied for biomedical matters. Ti–Nb–Sn alloys showed up as presenting great potential for the aforementioned purpose. The current study got Ti–35Nb-XSn alloys (x = 2.5; 5.0; 7.5) by applying the following techniques: arc melting, homogenizing and cooling in furnace, homogenizing and water quenched, hot rolling and water quenched. According to each step of the study, the microstructures were featured by means of optical microscopy, by applying a scanning electron microscopy (SEM) analysis as well as X-ray diffraction. The mechanical properties were gotten by means of: Vickers microhardness, tensile and ultrasonic tests. Their ratio between tensile strength and elastic modulus as well as the ductility were compared to other biomedical alloys already available in the literature. The mechanical behavior of the Ti–Nb alloys directly depends on the Sn rates that constitutes the phases as well as on the thermomechanical background to which the alloy was submitted to. The hot rolled Ti–35Nb–2.5Sn alloy showed high ratio between strength and elastic modulus as well as high ductility, just as high as those of some cold rolled Ti alloys.     

铸造钛合金及其熔炼技术的发展现状

钛合金具有密度低、高温性能好、耐腐蚀性能好等优点,逐渐成为一种优异的航空航天结构材料.综述了钛合金的成形特点和发展现状,以及钛合金熔炼技术的发展现状.     

Microstructure and mechanical properties of FexCoCrNiMn high-entropy alloys

The microstructure and tensile properties of Fe_xCoCrNiMn high-entropy alloys (HEAs) were investigated. It was found that the Fe_xCoCrNiMn HEA has a single face-centered cubic (fcc) structure in a wide range of Fe content. Further increasing the Fe content endowed the Fe_xCoCrNiMn alloys with an fcc/body-centered cubic (bcc) dual-phase structure. The yield strength of the Fe_xCoCrNiMn HEAs slightly decreased with the increase of Fe content. An excellent combination of strength and ductility was achieved in the Fe_xCoCrNiMn HEA with higher Fe content, which can be attributed to the outstanding deformation coordination capability of the fcc/bcc dual phase structure.