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China Foundry 2025年第1期22卷 33-44页

作者： Wei Yuan Hai-dong Zhao Xu Shen Chun Zou Yuan Liu Qing-yan Xu national engineering research Center of near-net-shape forming for metallic materials South China University of TechnologyGuangzhou 510640China Key Laboratory for Advanced materials Processing Technology(Ministry of Education) Tsinghua UniversityBeijing 100084China

Microporosity formed in the solidification process of Al alloys is detrimental to the alloy properties.A two-dimensional cellular automaton(CA)model was developed to simulate the microstructure and microporosity formation in Al-Cu alloys,considering variations in Cu content and solidification *** results indicate that the Cu content primarily influences the growth of *** validate the model,directional solidification experiments were conducted on Al-Cu alloys with varing Cu contents and withdrawal *** experimental results of dendrites and microporosity characteristics agree well with the predictions from the developed model,thus confirming the validity of the *** alloy’s liquidus temperature,dendrite morphology,and hydrogen saturation solubility arising from different Cu contents have significant effects on microporosity *** withdrawal rate primarily affects the nucleation of hydrogen microporosity by altering cooling rates and dendritic growth rates,resulting in different microporosity characteristics.

关键词： microporosity dendrites cellular automaton Al-Cu alloys directional solidification

Bonding mechanism of X10CrNi18-8 with Ni/Al_2O_3 composite ceramic by pressureless infiltration

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Journal of Central South University 2011年第4期18卷 953-959页

作者：杨少锋陈维平韩孟岩杨超朱德智 national engineering research Center of near-net-shape forming for metallic materials South China University of Technology

Abstract： An alloy steel/alumina composite was successfully fabricated by pressureless infiltration of X10CrNil8-8 steel melt on 30% （mass fraction） Ni-containing alumina based composite ceramic （Ni/Al2O3） at 1 600 ℃. The infiltration quality and interfacial bonding behavior were investigated by SEM, EDS, XRD and tensile tests. The results show that there is an obvious interfacial reaction layer between the alloying steel and the Ni/Al2O3 composite ceramic. The interfacial reactive products are （FexAly）3O4 intermetallic phase and （AlxCry）2O3 solid solution. The interracial bonding strength is as high as about 67.5 MPa. The bonding mechanism of X10CrNi 18-8 steel with the composite ceramic is that Ni inside the ceramic bodies dissolves into the alloy melt and transforms into liquid channels, consequently inducing the steel melt infiltrating and filling in the pores and the liquid channels. Moreover, the metallurgical bonding and interfacial reactive bonding also play a key role on the stability of the bonding interface.

关键词： pressureless infiltration steel/alumina composites interface bonding infiltration mechanism

Strength and ductility optimization of HPDC AlSi8MgCuZn2 alloys by modifying pre-aging treatment

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China Foundry 2024年第4期21卷 343-351页

作者： Yuan-hang Jiang Hui-ting Zheng Fei Liu Hai-dong Zhao national engineering research Center of near-net shape forming for metallic materials South China University of TechnologyGuangzhou 510641China

Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further improve their mechanical *** this study,two-stage aging treatment with different pre-aging times was designed and employed to further improve the mechanical properties of HPDC Al8SiMgCuZn *** characteristics of precipitates were evaluated by a transmission electron microscope(TEM),and the precipitation strengthening mechanism was *** results reveal that the strengthening is mainly contributed by the precipitation ofβ″phase after two-stage aging,and the number density and size of the precipitates are significantly depended on the pre-aging *** number density of precipitates is increased with the pre-aging time prolonged from 0 h to 4 h,and then decreases with the further increase of pre-aging time from 4 h to 6 *** precipitates with the highest density and smallest size are observed after pre-aging for 4 *** pre-aged at 100℃for 4 h and then artificial aged at 200℃for 30 min,the yield strength of 207 MPa,ultimate tensile strength of 325 MPa and elongation of 7.6%are achieved.

关键词： high pressure die cast aluminum alloy microstructural heterogeneity mechanical properties precipitation strengthening two-stage aging

Effect of zirconium on microstructures and mechanical properties of squeeze cast Al-5.0Cu-0.4Mn-0.1Ti-0.1RE alloy

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Journal of Central South University 2017年第10期24卷 2231-2237页

作者： MENG Fan-sheng ZHANG Wei-wen HU Yuan ZHANG Da-tong YANG Chao national engineering research Center of near-net-shape forming for metallic materials South China University of TechnologyGuangzhou 510640China

Al–5.0Cu–0.4Mn alloys with different Zr additions have been prepared by direct squeeze *** effects of Zr on microstructures and mechanical properties of the as-cast and T6 heat-treated alloys were investigated by tensile test,optical microscope(OM),scanning electron microscope(SEM)and transmission electron microscope(TEM).The results show that the optimal tensile property of the as-cast alloy occurs at the Zr content of 0.15%(mass fraction)due to the"Zr poisoning"action and the appearance of bulky primary Al_3Zr,which decreases the grain refinement strengthening effect of the as-cast *** peak values of ultimate tensile strength and yield strength of the T6 alloy occur at the Zr content of 0.25%,and that of the elongation occurs at Zr content of 0.05%.This is mainly attributed to the strengthening effect of dispersed precipitation of Al_3Zr and??*** optimal mechanical properties of T6 heat-treated alloy are the tensile strength of 429 MPa,the yield strength of 327 MPa and the elongation of 18%,respectively when the squeeze pressure is 100 MPa and Zr content is 0.25%.

关键词： Zr squeeze pressure mechanical property microstructure

Enhanced strength and ductility in Al-Zn-Mg-Cu alloys fabricated by laser powder bed fusion using a synergistic grain-refining strategy

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Journal of materials Science & Technology 2022年第29期124卷 41-52页

作者： Xiaohui Liu Yunzhong Liu Zhiguang Zhou Qiangkun Zhan national engineering research Center of near-net-shape forming for metallic materials South China University of TechnologyGuangzhou 510641China

Grain refinement is critical to surpassing the bottlenecks of inherent hot tearing of high-strength aluminum alloys fabricated by additive manufacturing(AM).In this study,a synergistic grain-refining strategy including heterogeneous nucleation,solute-driven growth restriction and nanoparticle-induced growth restriction was introduced to control the microstructure of Al-Zn-Mg-Cu alloys during the laser powder bed fusion(LPBF)***-free Al-Zn-Mg-Cu alloys with significantly refined grains were safely fabricated via LPBF by coincorporation of Ti C and ***-situ L1-AlTi particles were produced to promote the heterogeneous *** grain growth was restricted by adding Ti solute,while introduced TiC nanoparticles(NPs)improved the density of heterogeneous nucleation sites and blocked grain growth *** resultant elimination of columnar grains and hot cracks in the(1 wt.%)TiC-and(0.8 wt.%)TiH-modified Al-Zn-Mg-Cu alloy resulted in excellent ultimate tensile strength(UTS)of 593±24 MPa,yield strength(YS)of 485±41 MPa and elongation(EL)of 10.0%±2.5%under the T6 *** study provides new insights into improving the grain microstructure and mechanical properties of high-strength aluminum alloys during LPBF.

关键词： Grain refinement High-strength aluminum alloys Laser powder bed fusion(LPBF) Al-Zn-Mg-Cu alloy

Microstructure and mechanical properties of TiAl/Ni-based superalloy joints vacuum brazed with Ti-Zr-Fe-Cu-Ni-Co-Mo filler metal

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Rare Metals 2021年第8期40卷 2134-2142页

作者： Bao Wan Xiao-Qiang Li Cun-Liang Pan Dong-Yu Li Sheng-Guan Qu Chao Yang national engineering research Center of near-net-shape forming for metallic materials South China University of TechnologyGuangzhou510640China

For the purpose of elevated temperature service and weight reduction in aerospace vehicle applications,a novel Ti-Zr-Fe-Cu-Ni-Co-Mo filler metal was employed to join TiAl to Ni-based superalloy(GH536).The effects of brazing temperature on interfacial microstructure and chemical composition of the joints were *** representative joint microstructure from TiAl substrate to GH536 substrate was primarily composed of four characteristic layers in order:B_(2);Al_(3)NiTi_(2);AlNi_(2)Ti containing Cr-rich(Cr,Ni,Fe)_(ss)(subscript ss represents solid solution),Ni-rich(Ni,Cr,Fe)_(ss) and TiNi3;Cr-rich(Cr,Ni,Fe)_(ss)containing AlNi_(2)Ti,Ni-rich(Ni,Cr,Fe)_(ss) and *** IV has the majority of the brazing seam,while LayerⅡwas the *** the thickness of LayerⅡwas not affected by brazing *** the increase in brazing temperature in the range of 1110-1170℃,both the shear strength and the thickness of brazing seam firstly increased and then *** joint performance was jointly controlled by the thickness of brazing seam,the amounts of microcracks and intermetallic compounds formed in brazing *** maximum shear strength of 183 MPa at room temperature was obtained together with a peak thickness when the joint was brazed at 1150℃for 10 min and the shear fracture mainly occurred in the thinnest LayerⅡAl_(3)NiTi_(2).

关键词： TiAl alloy Ni-based superalloy Brazing Microstructure Shear strength

Microstructure and properties of ultra-fine tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering

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Transactions of Nonferrous Metals Society of China 2010年第3期20卷 443-449页

作者：李小强辛红伟胡可李元元 national metallic materials net-shape forming engineering research Center South China University of Technology

The microstructure and properties of the 93W-4Ni-2Co-1Fe(mass fraction,%) tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering from mixed elemental powders were *** 15 h milling,the average W grain size in the powders is decreased to 120 *** the powders milled for 15 h,the density,hardness and transverse rupture strength of the alloys sintered only by an intensive pulse electric current are the *** the total sintering time keeps constant,the properties of the sintered alloys can be obviously improved by optimizing the sintering time of pulse-and constant-currents.A bulk ultrafine alloy with an average W grain size of about 340 nm can be obtained by sintering 15 h-milled powders in a total sintering time of 6 *** corresponding sintered density,hardness and transverse rupture strength reach 16.78 g /cm3,HRA84.3 and 968 MPa,respectively.

关键词： 93W-4Ni-2Co-1Fe alloy mechanical alloying electric current activated sintering

Effect of Rolling on a Warm Compacted Ti_3SiC_2 Particulate Reinforced Cu Matrix Composite

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稀有金属材料与工程 2011年第S3期40卷 56-58页

作者： Ngai Tungwai national engineering research Center of near-net-shape forming Technology for metallic materials South China University of Technology

Warm compaction was employed to fabricate a Ti3SiC2 particulate reinforced copper matrix composite for electro-friction application. Copper matrix composite reinforced with 5wt% of copper-coated Ti3SiC2 particulates were prepared by compacting mixed powder with a pressure of 700 MPa at 145 ℃, and then sintered at 1000 ℃ under cracked ammonia atmosphere for 60 min. In order to improve the density, rolling process was applied on the sintered samples, their density, hardness, electrical conductivity, ultimate tensile strength and tribological behaviors were studied. Results showed that the rolled composite with 30% deformation has a density of 8.28 g/cm3, a hardness of 1060 MPa (HB), an ultimate tensile strength of 288 MPa, an electrical resistivity of 7.0 ×10-8 Ω·m and a friction coefficient of 0.17.

关键词： Cu-Ti3SiC2 composite powder metallurgy electro-friction material

Post-treatment Process of Semi-solid Powder Rolling

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Acta Metallurgica Sinica(English Letters) 2015年第10期28卷 1305-1315页

作者： Xia Luo Yun-Zhong Liu Bin Wang national engineering research Center of near-net-shape forming for metallic materials South China University of Technology School of materials Science and engineering Southwest Petroleum University

Semi-solid powder rolling is a strip manufacturing process, which combines powder rolling with semi-solid rolling in one step to prepare high-performance metallic strips. A total of 7050 aluminum alloy strips were prepared by semi-solid powder rolling and then used to study the post-treatment process and evaluate qualities of post-treated *** post-treatment processes involving sintering, pre-sintering-cold deformation-sintering, and hot rolling were used to process the semi-solid powder rolled strips. The results show that both swelling of pores and densification occur during solid-state sintering while microhardness increases. The decrease in density is due to that the swelling of pores has a larger effect on the density change than that of densification. The relative density reaches 92.6% with the maximum microhardness of 300 HV after ＇＇pre-sintering-cold deformation-sintering＇＇ process. High microhardness is due to the ultrafine secondary particles uniformly distributed within the grains. The microhardness and relative density of a hot rolled strip are 176 HV and 99%, respectively, and the secondary particles disappear. Occurrence of recrystallization in these three post-treatment processes makes the grains finer.

关键词： Semi-solid powder rolling Post-treatment Sintering Hot rolling Pore swelling

Simulation of α-Al grain formation in high vacuum die-casting Al-Si-Mg alloys with multi-component quantitative cellular automaton method

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China Foundry 2022年第2期19卷 99-108页

作者： Yong-zhi Hao Hai-dong Zhao Xu Shen Xue-ling Wang Hui-ting Zheng national engineering research Center of near-net-shape forming for metallic materials South China University of TechnologyGuangzhou 510641China

Al-Si-Mg alloys are the most commonly used material in high vacuum die-casting(HVDC),in which the morphology and distribution ofα-Al grains have important effect on mechanical properties.A multi-component quantitative cellular automaton(CA)model was developed to simulate the microstructure and microsegregation of HVDC Al-Si-Mg alloys with different Si contents(7%and 10%)and cooling rates during *** grain number and average grain size with electron backscatter diffraction(EBSD)analysis were used to verify the *** relationship between grain size and nucleation order as well as nuclei density was investigated and *** is found that the growth of grains will be restrained in the location with higher nuclei *** influence of composition and cooling rate on the solute transport reveals that for AlSi7Mg0.3 alloy the concentration of solute Mg in liquid is higher at the beginning of eutectic *** comparison between simulation and experiment results shows that externally solidified crystals(ESCs)have a significant effect for samples with high cooling rate and narrow solidification interval.

关键词： Al-Si-Mg alloys high vacuum die-casting cellular automaton α-Al grains external solidification crystals