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Effects of sonication amplitude on the microstructure and mechanical properties of AZ91E magnesium alloy

Journal of Magnesium and Alloys 2022年第12期10卷 3397-3405页

作者： P.Emadi B.Andilab C.Ravindran centre for near-net-shape processing of materials Ryerson University350 Victoria StreetTorontoON M5B 2K3 Canada

Light metals are gaining increased attention due to ecological sustainability concerns and strict emission regulations. Magnesium(Mg)is one such metal that has the potential to replace high density components, which can reduce emissions through lightweighting. However,the mechanical properties of Mg alloys must be improved for them to become viable candidates for structural applications. To this end, the current study examines the effect of sonication vibrational amplitude on the microstructure and mechanical properties of AZ91E Mg *** molten alloys were subjected to ultrasonic treatment at a frequency of 20 kHz, 180 s of processing time and vibrational amplitudes ranging from 1.25 to 15 μm. The resultant castings were characterized using optical microscopy, scanning electron microscopy and tensile testing. It was found that sonication with amplitudes up to 7.5 μm was able to effectively refine the secondary phases of the alloy. Similar trends were observed for grain size and yield strength. The refinement in microstructure was likely caused by the finer grain size and cavitation induced undercooling of the liquid metal. In addition, it was also noted that even the lowest level of amplitude(1.25 μm) was able to increase the density, improve the ultimate tensile strength and ductility of the castings. The tensile strength and ductility were thought to have been enhanced by ultrasonic degassing and refinement in microstructure, while the yield strength was improved through the Hall-Petch effect. The results from this study provided a basis for optimizing the sonication process and promoting its use in industry. As a result, Mg alloys improved through ultrasonic processing have the potential to replace higher density components, with consequent energy efficiency and environmental and ecological benefits.

关键词： Magnesium Casting and solidification Ultrasonic processing Vibrational amplitude Grain refinement Mechanical properties

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Research status and prospects of the fractal analysis of metal material surfaces and interfaces

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International Journal of Minerals,Metallurgy and materials 2025年第1期32卷 20-38页

作者： Qinjin Dai Xuefeng Liu Xin Ma Shaojie Tian Qinghe Cui Beijing Advanced Innovation Center for materials Genome Engineering University of Science and Technology BeijingBeijing 100083China Beijing Laboratory of Metallic materials and processing for Modern Transportation University of Science and Technology BeijingBeijing 100083China Laboratory for Advanced materials processing of Ministry of Education University of Science and Technology BeijingBeijing 100083China School of Mechanical and Electrical Engineering Xinjiang Institute of EngineeringUrumqi 830023China

As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine *** analysis has been used to characterize the shapes of metal materials at various scales and *** methods make it difficult to quantitatively describe the relationship between the regular characteristics and properties of metal material surfaces and ***,fractal analysis can be used to quantitatively describe the shape characteristics of metal materials and to establish the quantitative relationships between the shape characteristics and various properties of metal *** the perspective of two-dimensional planes and three-dimensional curved surfaces,this paper reviews the current research status of the fractal analysis of metal precipitate interfaces,metal grain boundary interfaces,metal-deposited film surfaces,metal fracture surfaces,metal machined surfaces,and metal wear *** relationship between the fractal dimensions and properties of metal material surfaces and interfaces is *** from three perspectives of fractal analysis,namely,research scope,image acquisition methods,and calculation methods,this paper identifies the direction of research on fractal analysis of metal material surfaces and interfaces that need to be *** is believed that revealing the deep influence mechanism between the fractal dimensions and properties of metal material surfaces and interfaces will be the key research direction of the fractal analysis of metal materials in the future.

关键词： metal material surfaces and interfaces fractal analysis fractal dimension homogeneity

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Effect of short-time low-temperature austenitizing on microstructure and mechanical properties of DT300 ultra-high strength steel fabricated by laser powder bed fusion

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Journal of Iron and Steel Research International 2024年第7期31卷 1763-1777页

作者： Chen-yang Jiang Xiao-qiang Li Jin-tao Wang Hao Luo Sheng-qing Gao Sheng-guan Qu Chao Yang National Engineering Research centre of near-net-shape Forming for Metallic materials South China University of TechnologyGuangzhou 510640GuangdongChina Institute of New materials Guangdong Academy of ScienceGuangzhou 510650GuangdongChina

To address the inhomogeneous microstructure and improve the mechanical properties of DT300 ultra-high strength steel specimens fabricated by laser powder bed fusion,different post-heat treatment schedules are *** the increase in austenitizing temperature and time,the migration rate of austenite grain boundaries continuously increases with the dissolution of nano-carbides,and the formation of nano-oxides and twin martensite is also inhibited *** rapid growth in the size of prior austenite grains and martensite laths,as well as the decrease in the content of nano-oxides and twin martensite,led to a rapid decrease in the strength(yield strength and ultimate tensile strength)from HT2 to HTF *** HT1 specimens(austenitizing at 830℃for 30 min,then oil quenching and tempering at 300℃for 120 min and finally air cooling)display excellent mechanical properties of yield strength of 1572 MPa,ultimate tensile strength of 1847 MPa,elongation of 9.84%,and fracture toughness of 106 MPa m^(1/2),which are counterparts to those of conventional DT300 steel forgings after heat treatment.

关键词： DT300 ultra-high strength steel Laser powder bed fusion-Short-time low-temperature austenitizing Microstructure Mechanical property

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Effect of sintering temperature on the preparation of Cu-Ti3 SiC2 metal matrix composite

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Progress in Natural Science:materials International 2013年第1期23卷 70-76页

作者： Tungwai L.Ngai Wei Zheng Yuanyuan Li National Engineering Research Center of near-net-shape Forming Technology for Metallic materials South China University of Technology

Ti3SiC2 has the potential to replace graphite as reinforcing particles in Cu matrix composites for applications in brush,electrical contacts and electrode *** this paper the fabrication of Cu-Ti3SiC2 metal matrix composites prepared by warm compaction powder metallurgy forming and spark plasma sintering(SPS) was *** stability of Ti3SiC2 at different sintering temperatures was also *** present experimental results indicate that the reinforcing particles in Cu-Ti3SiC2 composites are not stable at and above 800℃.The decomposition of Ti3SiC2 will lead to the formation of TiC and/or other carbides and *** purity is the major concern,the processing and servicing temperatures of the Cu-Ti3SiC2 composite should be limited to 750℃ or *** composites prepared by warm compaction forming and SPS sintering at 750℃ have lower density when compared with the composites prepared by SPS sintering at 950℃,but their electrical resistivity values are very close to each other and even lower.

关键词： Warm compaction Spark plasma sintering Electrical conductivity Mechanical property Impurity

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Improvement of impact properties of Al-Si-Mg alloy via solution treatment and joint modification with Sr and La

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Rare Metals 2024年第7期43卷 3301-3313页

作者： Xiong-Ling Zheng Shao-Xiang Li Jia-Le Ma Qing-Yan Xu Hai-Dong Zhao Zhi-Qiang Han Key Laboratory for Advanced materials processing Technology Ministry of EducationSchool of Materials Science and EngineeringTsinghua UniversityBeijing 100084China National Engineering Research Center of near-net shape Forming for Metallic materials South China University of TechnologyGuangzhou 510641China

An effort to obtain superior impact properties for Al-7Si-0.35 Mg alloy is presented,where modification with 0.02 wt% Sr and 0.1 wt% La as well as solution treatment was jointly *** samples were solution treated at 535℃ for 15 min to 12 *** microstructure,fracture mechanism,and their correlation with the impact properties of the alloy were studied in detail mainly through optical microscopy(OM),scanning electron microscopy(SEM) and oscillography impact *** results show that the addition of Sr and La refined the eutectic Si particles significantly from~ 2.05 μm(modified with Sr alone) to~ 0.75 μm in as-cast microstructure,leading to a very homogeneous distribution of spheroidized Si particles in the alloy solution treated at 535℃ for 8 *** alloy exhibits excellent impact toughness up to 75 J·cm^(-2),which is much higher than the maximum impact toughness of the alloys modified by Sr alone(~ 46 J·cm^(-2)).The major reason for this remarkable increase in the impact property is the dramatic increase in crack initiation *** dispersoid-free zones(DFZs)near the eutectic regions mainly consist of the ductile Al-matrix,which exhibits excellent *** ductile Al-matrix of the DFZs hinders the crack propagation,resulting in a significant increase in crack propagation energy.

关键词： Aluminum alloys Modification Solution treatment Microstructure Impact properties Fracture mechanism

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Wetting behaviors and interfacial characteristics of molten Al_(x)CoCrCuFeNi high-entropy alloys on a WC substrate

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Journal of materials Science & Technology 2021年第19期78卷 192-201页

作者： Wenyan Luo Yunzhong Liu Cheng Tu Guangdong Provincial Key Laboratory for processing and Forming of Advanced Metallic materials South China University of TechnologyGuangzhou510641China National Engineering Research Center of near-net-shape Forming for Metallic materials South China University of TechnologyGuangzhou510641China

The wettability of molten Al_(x)CoCrCuFeNi(x is from 0 to 1.5,mol.%)high-entropy alloys(HEA)on a WC substrate was measured using a modified sessile drop method at 1823 K in an argon *** wetting behaviors and interfacial characteristics between HEAs and WC were *** wettability with final equilibrium contact angles of 0.5°-4.6°is obtained,and addition of Al deteriorates the wettability of the *** wetting of Al_(x)CoCrCuFeNi/WC system can be roughly divided into an initially sharp spreading stage and a subsequent steady-state *** the first stage,the adsorption of Cr atoms at the solid-liquid interface primarily contributes to the wetting,and the contact angle drastically ***,both the wetting behavior and interfacial microstructure are determined by the Al content of the HEA in the next *** x≤0.5,the wetting is mainly driven by the dissolution of WC,although a few reaction products of(W,Cr)_(2)C are ***,an obvious dissolution pit appears at the surface of the *** the Al content of x≥1,the interfacial reaction is dominant in competition with the dissolution of WC,and massive reaction products precipitate at the HEA/WC interface,which leads to the formation of a continuous reaction layer.

关键词： Wetting High-entropy alloy Interface Microstructure Tungsten carbide

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Microstructural evolution and mechanical properties of Alloy 718 fabricated by selective laser melting following different post-treatments

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Rare Metals 2021年第11期40卷 3222-3234页

作者： Hao Luo Xiao-Qiang Li Cun-Liang Pan Peng-Jiang He Ke-Li Zeng National Engineering Research Center of near-net-shape Forming for Metallic materials South China University of TechnologyGuangzhou 510640China Institute of materials and processing Guangdong Academy of SciencesGuangzhou 510650China Dongguan Hyperpowder Co.Ltd. Dongguan 523808China

In this study,Alloy 718 specimens were fabricated via selective laser melting(SLM),and the effects of different post-treatments on microstructures and mechanical properties of the alloy were systematically *** post-treatment techniques investigated were solid solution+dual aging(SA) and hot isostatic pressing+solid solution+dual aging treatment(HIP+SA).The results indicate that the specimens treated using SA have a columnar crystal structure similar to the as-built sample,the microstructure is partially recrystallized,and the grain size increases ***,the grain morphology is dominated by equiaxed crystals in samples treated using HIP+SA,and the microstructure is completely recrystallized,with distinct grain coarsening and a large number of twins *** treated using SA and HIP+SA show high tensile strength and yield strength and excellent elongation at room temperature,which can be primarily attributed to the strengthening of the γ’ and γ "precipitated *** number of γ" precipitated phases are reduced due to the consumption of Nb to form a large amounts of δ phase and(Ti,Nb)C carbides,resulting in the strength of HIP+SA specimens being lower than that of SA specimens.

关键词： Selective laser melting Alloy 718 Post-treatments Microstructural evolution Mechanical properties

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Modeling the hot working behavior of near-α titanium alloy IMI 834

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Progress in Natural Science:materials International 2013年第6期23卷 598-607页

作者： I.Balasundar T.Raghu B.P.Kashyap near net shape Group Aeronautical Materials DivisionDefence Metallurgical Research Laboratory Department of Metallurgical Engineering and materials Science Indian Institute of Technology Bombay

The hot working behavior of near-a titanium alloy IMI 834 with a duplex starting microstructure was studied using the technique of processing *** processing map was interpreted in terms of the microstrucmral processes occurring during deformation,based on the values of dimensionless parameter η which represents the energy dissipation through microstructural *** instability criterion(ξprocessing *** the parameters(η and ξ) were computed using the experimental data generated by carrying out hot compression tests over a range of temperatures(850-1060℃) and strain rates(3×10-1/s).The deterministic domains observed under the investigated temperature and strain rate conditions were attributed to continuous dynamic recrystallization or globularisation of a lamellae,dynamic recrystallization and growth of β grains through microstructural *** unified strain compensated constitutive equation was established to describe the hot working behavior of the material in the selected temperature-strain rate *** established constitutive equation was validated using standard statistical parameters such as correlation coefficient and average absolute relative error.

关键词： Titanium alloys IMI 834 Hot working processing maps Constitutive modeling

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Microstructures and mechanical properties of WE43 magnesium alloy prepared by friction stir processing

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Rare Metals 2020年第11期39卷 1267-1272页

作者： Jin Li Da-Tong Zhang Fang Chai Wen Zhang National Engineering Research Center of near-net-shape Forming for Metallic materials South China University of TechnologyGuangzhou510640China

Mg-3.99Y-3.81Nd-0.53 Zr(WE43)casting alloy was subjected to single-pass friction stir processing(FSP)at a constant processing speed of 60 mm-min^(-1)and various rotation speeds of 400,800,1200,and 1500 r·min^(-1),and microstructures and mechanical properties of the experimental materials were *** results in the generation of fine-grained microstructure,and fundamental breakage and dissolution of the coarse second *** the rotation speeds increasing,the average grain size of the FSP specimen in the stir zone first decreases and then increases,and the finest microstructure(~2μm)was prepared at the rotation speed of 800 r·min^(-1).Owing to the finer and more uniform microstructure,the mechanical properties of WE43 alloy after FSP are significantly *** variation tendency of the tensile properties is consistent with the change of the grain *** maximum tensile strength,elongation,and average microhardness of the FSP WE43 alloy obtained at 800 r·min^(-1)are 290 MPa,17.2%,and HV92.9,*** fracture morphology shows that small dimples can be observed on the FSP specimens,while the as-cast alloy fails through cleavage fracture.

关键词： WE43 magnesium alloy Friction stir processing Microstructure mechanical property Rare earth elements

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processing and mechanical properties of network ceramic/steel composites by pressureless infiltration

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Journal of Central South University 2014年第7期21卷 2560-2566页

作者：杨少锋陈维平王再友蔡云杰 School of Material Engineering Nanjing Institute of Technology National Engineering Research Center of near-net-shape Forming for Metallic materials South China University of Technology

A new style Ni-containing alumina ceramic foam based continuous three-dimensional interconnected skeleton was prepared by impregnating a polymeric sponge with aqueous ceramic ***,alumina ceramic foam/steel metal matrix composites(MMCs) were prepared successfully by sand mold casting *** microstructure and mechanical properties of MMCs were investigated by SEM,EDS and compressive *** results show that the depth of infiltration is about 40 μm to the bonding interface of ceramic/steel and the fracture strength σmax and plastic strain limit εp of composite are 520 MPa and 11.2%,*** fretting wear mechanism of MMCs is mainly performed at the oxidative wear mode with lower load/friction frequency and the predominant oxidation wear together with slight adhesive wear and abrasive wear multiple mode with higher load/ friction ***,the infiltration bonding and continuous three-dimensional interconnected ceramic skeleton play a vital role in the stability of the bonding interface and excellent mechanical properties.

关键词： network ceramic steel composite bending strength fretting wear

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