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1.
Cijun Shuai Lianfeng Xue Chengde Gao Youwen Yang Yanru Zhang 《Virtual and Physical Prototyping》2018,13(3):146-154
Zn possesses good biodegradability and biocompatibility, but its strength and hardness are insufficient for bone implants. In this study, Ag was introduced into Zn to improve the mechanical properties by selective laser melting. The results showed that Ag was dissolved in Zn, which generated constitutional undercooling in front of the advancing solid/liquid interface during solidification, making more nucleation events occur and thus refining the grains. When Ag content exceeded its solid solubility in Zn, AgZn3 phase is formed, which acted as active nucleation sites for Zn grains, further refining the grains. The refinement of the grains effectively hindered the plastic deformation and dislocation. As a result, the compressive strength and hardness were improved by about 100% and 116%, respectively. When Ag content continued increasing and became excessive, AgZn3 phase grew rapidly, coarsening the grains. Accordingly, the mechanical properties slightly decreased. These results demonstrated that the Zn–Ag alloys are potential implant biomaterials. 相似文献
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The influence of selective laser melting (SLM) process parameters (laser power, scan speed, scan spacing, and island size using a Concept Laser M2 system) on the porosity development in AlSi10Mg alloy builds has been investigated, using statistical design of experimental approach, correlated with the energy density model. A two-factor interaction model showed that the laser power, scan speed, and the interaction between the scan speed and scan spacing have the major influence on the porosity development in the builds. By driving the statistical method to minimise the porosity fraction, optimum process parameters were obtained. The optimum build parameters were validated, and subsequently used to build rod-shaped samples to assess the room temperature and high temperature (creep) mechanical properties. The samples produced using SLM showed better strength and elongation properties, compared to die cast Al-alloys of similar composition. Creep results showed better rupture life than cast alloy, with a good agreement with the Larson–Miller literature data for this alloy composition. 相似文献
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Previous studies have reported that high carbon contents in FeCoCrNiMn high-entropy alloys lead to carbides precipitating from the alloys. Typically, carbides are used to improve the strength of alloys but also lead to decreased ductility. However, the strength and ductility of alloys can be improved when carbides shape, size and distribution are carefully controlled. Therefore, a carbide-containing FeCoCrNiMn alloy with 2?at.-% carbon was prepared by arc melting, and its microstructure and mechanical properties were further tuned by cold rolling with subsequent annealing treatment. The yield strength and uniform elongation of the resultant alloy were excellent, reaching 581?MPa and 25%, respectively, due to the additive combination of various strengthening mechanisms, such as solid-solution hardening, grain-boundary hardening and precipitation hardening. 相似文献
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为改善激光熔化沉积TC31高温钛合金力学性能,本文通过光学显微镜、SEM、TEM和力学性能测试的方法研究了退火温度对合金中组织演化行为的影响,及其与合金室温和650 ℃高温力学性能的关系。结果表明:组织中初生α相含量随着退火温度升高而降低,其溶解主要发生在950 ℃以上,980 ℃退火后含量仅为29%。当退火温度超过930 ℃时,初生α相片层宽度明显增加。随着退火温度升高,α/β界面处析出的(Ti, Zr)6Si3相尺寸增加,且进入α相片层内部。合金在800~1 000 ℃退火时,合金室温拉伸屈服强度随退火温度升高趋于降低。受相界面析出的硅化物聚合长大及α相片层尺寸增加等因素影响,合金高温屈服强度随退火温度升高先降低后增加。合金经过1 000 ℃退火后,呈现良好的高温性能,其650 ℃下抗拉强度达657 MPa、屈服强度约为466 MPa、延伸率27%。 相似文献
5.
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. 相似文献
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Two Fe–Mn alloys with relatively low Mn content were designed. The microstructure characteristics and resultant mechanical properties were investigated in detail by means of electron back-scattered diffraction, transmission electron microscopy and X-ray diffraction. The results show that the formation of α′-martensite is effectively suppressed and the yield strength and total elongation are significantly enhanced by increasing Mn content from 12 to 13 mass%. A great amount of α′-martensite can effectively enhance strain hardening rate, but they deteriorate ductility. The austenite grain is always divided by multiple-variant ?-martensite plate. In addition, the prior austenite grain boundaries and austenite/?-martensite interfaces can act as obstacle to suppress the growth of ?-martensite plates. 相似文献
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《Materials Science & Technology》2013,29(1):449-452
AbstractThis study details the development of microstructure of Ti14 alloy as a function of the forging temperature and forging ratio in semisolid state and influence of resulting microstructure on the mechanical properties. The results reveal that dynamic recrystallisation occurred during semisolid forging, and the grain refinement was attained. Grain size increased in the forging temperature and decreased in the forging ratio. High ultimate tensile strengths and low elongation have been achieved after semisolid forging. The strength decreased with increasing forging temperature, while the ductility increased with increasing forging ratio. The relative contributions of tensile properties were attributed to the varieties of grain size obtained by thixoforging. 相似文献
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In this study, mechanical behaviour and microstructural evolution in friction stir processing (FSP) of casting hypereutectic A390 aluminium alloy have been investigated. The mechanical behaviour of FSP samples was investigated by measuring the strain rate sensitivity using shear punch testing. The room-temperature shear punch tests were conducted at shear strain rates in the range of 10?4–10?1?s?1. The results indicate that the strain rate sensitivity index increases from about 0.015 to 0.120 for as-cast A390 after third FSP pass and then experiences a further growth in FSP passes. The increase in the grain size and CuAl2 intermetallic particle size result in a reduction in strain sensitivity index as well as shear strength after third FSP pass. 相似文献
10.
Zhengwen Yu Mengdie Hu Mingsong Wu Jiejun He Zhengyuan Gao 《Materials Science & Technology》2017,33(17):2086-2096
In this paper, the effect of aluminium on microstructure and mechanical properties of as-cast magnesium–manganese alloy has been investigated by means of X-ray diffraction, optical microscopy and scanning electron microscopy. The results reveal that various Al–Mn intermetallic compounds form with an increase of Al content. As a result, microstructure of AM11 alloy has been effectively refined due to the formation of Al8Mn5 phase along the grain boundary, while Al addition is explained as the main reason on refining the microstructure of AM91 alloy due to its higher grain growth restriction factor value of ~4.32. The tensile yield strength (TYS) has been improved steadily from 27.4 to 122.9?MPa with increasing Al content, because of the combined effects of grain boundary strengthening, solid solution strengthening and precipitation hardening behaviours. 相似文献
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为了研究Nb元素对Ti-10Mo合金组织和性能的影响,采用钨电极熔化、离心浇注工艺制备了4种钛合金(Ti-10Mo-XNb,X=0,3,7,10),分析并测试了Nb元素对Ti-10Mo合金铸态组织和力学性能的影响.研究结果表明:随着Nb含量的增加,3种Ti-Mo-Nb合金的铸态组织和相组成发生了改变,Ti-10Mo-3Nb合金由等轴的α+β晶粒组成,Ti-10Mo-7Nb合金由等轴的β晶粒组成,Ti-10Mo-10Nb合金由少量等轴和大量枝状的β晶粒组成.另外,随着Nb含量的增加,3种Ti-Mo-Nb合金的维氏硬度、压缩强度、弹性模量降低,压缩率和抗弯强度升高,压缩断口和弯曲断口由脆性断裂向韧性断裂转变.Ti-Mo-Nb合金有望成为新型的生物医用材料. 相似文献
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Selective laser melting technology is used to manufacture porous and solid AZ91D alloys. The effects of laser power and hatch spacing on the density, blowholes, microstructure and mechanical properties of AZ91D alloy are studied. The laser power and hatch spacing play a significant role in the density and blowholes of AZ91D specimens. The grains size of specimens increases from 1 μm–2 μm to 8 μm–10 μm from the bottom to the top in single molten pool. Compared with grain size of die‐casting alloy (30 μm), that of selective laser melted gets refinement. There is no significant change in microstructure in the bottom, middle and top of specimens. The micro‐hardness of AZ91D alloy, reaching up to 115.3 HV 0.1, is superior to that of die‐casting alloy (56 HV 0.1). The compression properties of porous and solid specimens reach the degree of die‐casting solid magnesium alloy. AZ91D alloy shows the potential in the application of medical biodegradable materials. 相似文献
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A series of Al–7Si–(0–5)Zn alloys were produced by permanent mould casting and their microstructure, mechanical and tribological properties were investigated in as-cast state. The microstructure of Al–7Si alloy consisted of α-Al dendrites surrounded by eutectic Al–Si mixture and a small amount of primary silicon particles. Addition of zinc into Al–7Si alloy resulted in the formation of α-solid solution and an increase in size and volume fraction of primary silicon particles. Moreover, these particles gathered inside interdendritic regions of the ternary Al–7Si–Zn alloys. The density, strength and hardness of Al–7Si–Zn alloys increased continuously with increasing zinc content, but their elongation to fracture and impact energy showed a reverse trend. It was also observed that zinc had no significant effect on the friction coefficient of the alloys, but their wear volume decreased with increasing zinc content up to 4%, above which the trend reversed. The wear surfaces of the alloys were characterized mainly by smearing layer with some degree of oxidation. In addition, delamination and fine scratches were observed on the worn surface. It was concluded that the addition of zinc up to 4% improves both mechanical and wear behaviour of Al–7Si alloy. 相似文献
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Paul Stavroulakis Anagnostis Toulfatzis Athanasios Vazdirvanidis Spyros Papaefthymiou 《Materials Science & Technology》2020,36(8):939-948
ABSTRACTCu–Ni–Si alloys exhibit a good combination of strength and electrical conductivity and may be a potential candidate for utilisation in electrotechnical applications. In this work, the mechanical behaviour and its relation to the microstructure of a Cu–Ni–Si alloy, subjected to different solution heat treatment cycles, were investigated. Tensile, bend and hardness testing, in addition to Optical and Scanning Electron Microscopy, were employed, as the main analytical techniques, in the context of the present investigation.This paper is part of a Thematic Issue on Copper and its Alloys. 相似文献
16.
The effects of Sn addition on the as-cast microstructure, mechanical properties and casting fluidity of the ZA84 magnesium alloy are investigated. The results indicate that adding 0.5–2.0 wt.%Sn to the ZA84 alloy not only can result in the formation of Mg2Sn phase but also can refine the Mg32(Al, Zn)49 phase and suppress the formation of Mg32(Al, Zn)49 phase, and with the increase of Sn amount from 0.5 wt.% to 2.0 wt.%, the morphology of Mg32(Al, Zn)49 phase gradually changes from coarse continuous and/or quasi-continuous net to relatively fine quasi-continuous and/or disconnected shapes. In addition, adding 0.5–2.0 wt.%Sn to the ZA84 alloy can improve the tensile and creep properties, and casting fluidity of the alloy. Among the Sn-containing ZA84 alloys, the ZA84 alloy added 1.0 wt.%Sn exhibits the best ultimate tensile strength, elongation and casting fluidity while the ZA84 alloy added 2.0 wt.%Sn has the best yield strength and creep properties. 相似文献
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S. Raghavan Baicheng Zhang Pei Wang Mui Ling Sharon Nai Tao Li 《Materials and Manufacturing Processes》2017,32(14):1588-1595
The microstructure and tensile properties of selective laser melted (SLM) Inconel 718 alloy were studied in the as-printed and different heat treat conditions. The SLM as-print microstructures exhibited columnar grain structures with very fine dendritic structure with segregation of elements. Apart from the standard heat treatment, three other heat treat cycle variants were carried out in an attempt to remove the extensive segregation of elements and modify the textured grain structure of the SLM as-print microstructure. Increasing the homogenization temperature reduced the segregation and coarsened the grain structure. However, the grains still remained columnar, and the material became softer with reduction in strength. After the ageing treatment, the tensile strength improved significantly for all the heat treated samples, which is typical for precipitation hardening of IN718 alloy. The microstructures of the heat treated samples exhibited the needle shaped δ, carbides, and finely dispersed γ″, γ′ phases. 相似文献
19.
Friction stir welding (FSW) was used to join Ti–6Al–4V alloy in air and under intense cooling conditions. The results show that the application of liquid nitrogen is beneficial in decreasing the peak temperature and in reducing the extent of the high-temperature region during welding, leading to a smaller stir zone (SZ). Intense cooling can lead to refined and homogeneous grains in the SZ, resulting in increased microhardness. The FSW joint produced with intense cooling had a tensile strength of 1020?MPa, which is nearly equivalent to that of the base material and is up to 2.6% higher than for the air-cooled joint. The fractographs for both types of joint were characterised by dimples, indicating that the fractures were ductile. 相似文献
20.
研究了Al含量变化对高Nb-TiAl合金的凝固组织与力学性能的影响.结果表明:随着Al含量的增加,TiAl合金晶粒尺寸呈增加趋势;当Al含量为45.7%时,凝固过程中局部区域发生包晶转变,使晶粒尺寸显著增大;室温及700℃高温拉伸强度随着Al含量的增加而呈增加的趋势,但发生包晶转变致使室温及700℃高温拉伸强度下降约200MPa;Al含量对延伸率不敏感,持久性能随Al含量的增加呈增加趋势.为控制铸锭凝固后的组织与力学性能,尽量避开包晶转变区,合金中Al含量应低于45.7%. 相似文献