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Characteristics and distribution of microstructures in high pressure die cast alloys with X-ray microtomography:A review

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China Foundry 2024年第5期21卷 427-444页

作者： hai-dong zhao Xue-ling Wang Qian Wan Wen-hui Bai Fei Liu School of Mechanical and Automotive Engineering South China University of TechnologyGuangzhou 510640China

Al and Mg alloy high pressure die castings(HPDC)are increasingly used in automotive *** microstructures in the castings have decisive effect on the casting mechanical properties,in which the microstructure characteristics are fundamental for the investigation of the microstructure-property *** the past decade,the microstructure characteristics of HPDC Al and Mg alloys,especially micro-pores andα-Fe,have been investigated from two-dimensional(2D)to threedimensional with X-ray micro-computed tomography(μ-CT).This paper provides an overview of the current understanding regarding the 3D characteristics and formation mechanisms of microstructures in HPDC alloys,their spatial distributions,and the impact on mechanical ***,it outlines future research directions for the formation and control of heterogeneous microstructures in HPDC alloys.

关键词： high pressure die casting microstructure three-dimensional characteristics distribution Al and Mg alloys

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

Three-dimensional characteristics of Fe-rich intermetal ics in gravity-cast Al-6Si alloys

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China Foundry 2017年第5期14卷 379-385页

作者： Chen Hu Wen-feng Luo hai-dong zhao National Engineering Center for Metallic Materials Net-shape Forming South China University of TechnologyGuangzhou 510640China

Fe-rich intermetallics, especially β-Fe phase, usually forming in the microstructure of cast aluminum alloys, are very detrimental to mechanical properties. In the present work, the effects of Fe content on phase transformation and microstructures were analyzed using a 3D X-ray microscope. Based on the highresolution 3D X-ray computed tomography, the 3D characteristics of Fe-rich intermetallics and micropores in the gravity-cast Al-6 Si alloys with different Fe contents were investigated. In addition, the effect of intermetallics on the microporosity was discussed. The results show that with increasing the Fe content from 0.10 wt.% to 0.60 wt.%, the volume fraction of Fe-rich intermetallics and the volume of the largest size Fe-rich intermetallic increased, and the 3D morphology of intermetallics changed from fine flake to network aggregation. As the Fe contents increased, the shrinkage pores were characterized, which were rather complex due to the micropores promoted by the intermetallics interactions.

关键词： Fe-rich intermetallics 3D X-ray computed tomography micropores Al-Si alloy

Cu含量和热处理工艺对Al-Si-Mg-Mn-xCu铸造铝合金显微组织和力学性能的影响

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Transactions of Nonferrous Metals Society of China 2024年第3期34卷 737-754页

作者：贾志宏周广文周宏宇刘飞丁立鹏翁瑶瑶向开云赵海东南京工业大学先进轻质高性能材料研究中心南京211816 重庆大学材料科学与工程学院重庆400044 江苏大学材料科学与工程学院镇江212013 华南理工大学国家金属材料近净成形工程技术研究中心广州510640 南京工程学院材料科学与工程学院南京211167

采用三维X射线显微镜、光学显微镜、扫描电子显微镜、透射电子显微镜及硬度测试系统研究Cu含量及热处理工艺对真空压铸Al-Si-Mg-Mn-xCu合金显微组织和力学性能的影响。研究发现,虽然Cu含量增加会提高铸锭中气孔的密度和尺寸,但是Cu添加... 详细信息

采用三维X射线显微镜、光学显微镜、扫描电子显微镜、透射电子显微镜及硬度测试系统研究Cu含量及热处理工艺对真空压铸Al-Si-Mg-Mn-xCu合金显微组织和力学性能的影响。研究发现,虽然Cu含量增加会提高铸锭中气孔的密度和尺寸,但是Cu添加将促进凝固过程中含Cu初生相(Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu)的形成,从而提高合金性能。合金中形成5种不同结构的初生相,包括共晶Si、α-Al(Fe,Mn)Si、β-Mg_(2)Si、Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu相。随着Cu含量增加,θ相的面积分数迅速增加,α-Al(Fe,Mn)Si相面积分数首先降低,随后缓慢增加,而Q相的变化趋势与α-Al(Fe,Mn)Si相相反。这些初生相在热处理过程中会出现不同的演变规律。在随后的时效处理过程中,Q'和θ'相的协同析出能显著提高合金的时效硬化潜力。

关键词：铝硅铸造合金真空压铸热处理显微组织力学性能初生相

Influence of intensification pressures on pores in die-cast ADC12 alloys

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China Foundry 2019年第3期16卷 184-189页

作者： Chun-tao Wang Jie Yao hai-dong zhao Run-sheng Yang Ningbo Heli Mould Technology Co. Ltd. Industrial Park Xiangshan County Ningbo 315700 China National Engineering Research Center of Near-net Shape Forming for Metallic Materials South China University of Technology Guangzhou 510641 China

Die casting process is widely applied in making Al parts. However, due to high speed of liquid metal flow in the die cavity, gases are prone to be entrapped in the filling, resulting in porosity defects. The X-ray computed tomography scanning technique was used to detect the pores in die-cast ADC12 alloys with different intensification pressures. The three-dimensional features of pores including pore size, number, sphericity have been obtained. The effect of different intensification pressures on two different kinds of pores, namely gas-pores and shrinkage pores, was analyzed. The results show that with increasing the pressure, the pore fractions and quantity gradually decrease. When the pressure increased to 85 MPa, the pores from gas entrapment during the mold filling were compressed, leading to a lower porosity fraction. The pressure cannot affect the pores in the samples with a thin wall (2 mm) due to a great solidification rate.

关键词： die casting intensification pressure porosity X-ray computed tomography

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

Greatly enhanced mechanical properties of thermoelectric SnSe through microstructure engineering

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Journal of Advanced Ceramics 2023年第5期12卷 1081-1089页

作者： Chen Chen Bin-Hao Wang Chen Chen hai-dong zhao Bin Zhang Dan Wang Tao Shen Peng-Hui Li Song zhao dong-Li Yu Yong-Jun Tian Bo Xu Center for High Pressure Science(CHiPS) State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China School of Physical Sciences Great Bay UniversityDongguan 523000China

The outstanding thermoelectric material, SnSe, is also known for its inferior mechanical properties, which bring great inconvenience for its application in thermoelectric devices. In this work, SnSe bulks were prepared via a sequential procedure of high-pressure synthesis (HPS), ball milling, and spark plasma sintering (SPS). The produced polycrystalline samples with a unique microstructure of tightly-bound quasi-equiaxed grains exhibited excellent mechanical properties. The Vickers hardness (HV), compressive strength (σ_(c)), and bending strength (σ_(b)) reached 1.1 GPa, 300 MPa, and 90 MPa, respectively, all of which are far superior to those of ordinary polycrystalline SnSe. Furthermore, the microstructures did not deteriorate thermoelectric performance. This work demonstrated an effective procedure to prepare polycrystalline microstructure-engineered SnSe materials, which not only show advantages in device applications but also shed light on property enhancement for other layer-structured thermoelectric materials.

关键词： thermoelectric materials SnSe mechanical properties hardness

Hydrogen storage thermodynamics and kinetics of as-cast Ce-Mg-Ni-based alloy

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Journal of Iron and Steel Research International 2024年第3期31卷 752-766页

作者： Yan Qi Xin Zhang Jun Li dong-liang zhao Shi-hai Guo Yang-huan Zhang Department of Functional Material Research Central Iron and Steel Research InstituteBeijing 100081China China Rare Earth New Material(Weishan)Co..Ltd. Jining 277600ShandongChina Collaborative Innovation Center of Integrated Exploitation of Bayan Obo Multi-Metal Resources Inner Mongolia University of Science and TechnologyBaotou 014010Inner MongoliaChina

The reaction kinetics of alloys based on magnesium are known to be greatly improved by the partial substitution of Mg with rare earths and transition metals,particularly *** enhanced superficial hydrogen dissociation rate,the weakened Mg-H bond and the lower activation energy following element replacement are thought to be related to the better *** experimental alloys Ce5Mg_(95-x)Ni_(x)(x=5,10,15)were smelted by the vacuum induction *** phase transformation and structural evolution of experimental alloys before and after reaction with hydrogen were char-acterized by X-ray diffraction,scanning electron microscopy and transmission electron *** cast specimens contain CeMg_(12),Mg and Mg_(2)Ni phases,and the increase in Ni content results in an obvious growth of Mg_(2)Ni *** isothermal and non-isothermal hydrogenation and dehydrogenation kinetics of the experimental specimens were investi-gated using the Sievert apparatus,differential scanning calorimetry and thermal gravimetric *** activation energy may be calculated using the Arrhenius and Kissinger *** experimental alloys have been shown to have good activation properties,with a reversible hydriding and dehydriding capacities of around 5.0 wt.%in the first *** initial dehydrogenation temperature of MgH_(2) decreases from 557.5 to 537.7 K with changing Ni content from 5 to 15 at.%.The dehydrogenation activation energy also reduces from 77.09 to 62.96 kJ/mol,which explains the improved hydrogen storage performance caused by Ni *** can be shown that the impact of Ni on the decomposition enthalpy of MgH_(2) is quite modest,with the absolute enthalpy(ΔHr)only decreasing from 78.48 to 76.15 kJ/mol.

关键词： Mg-based alloy Ni content Hydrogen storage kinetics Thermodynamic property Activation energy

Caseinolytic mitochondrial matrix peptidase X is essential for homologous chromosome synapsis and recombination during meiosis of male mouse germ cells

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Asian Journal of Andrology 2024年第2期26卷 165-174页

作者： hai-Wei Feng Yu zhao Yan-Ling Gao dong-Teng Liu Li-Jun Huo Key Laboratory of Agricultural Animal Genetics Breeding and ReproductionEducation Ministry of ChinaCollege of Animal Science and TechnologyHuazhong Agricultural UniversityWuhan 430070China Shenzhen Key Laboratory of Fertility Regulation Reproductive Medicine CenterThe University of Hong Kong-Shenzhen HospitalShenzhen 518053China Maternal-Fetal Medicine Institute Department of Obstetrics and GynaecologyShenzhen Baoan Women's and Children's HospitalJinan UniversityShenzhen 518100China Department of Obstetrics and Gynaecology Li Ka Shing Faculty of MedicineThe University of Hong KongHong Kong SARChina

Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various *** mitochondrial protease complex(ClpXP),which consists of caseinolytic mitochondrial matrix peptidase X(ClpX)and caseinolytic protease P(ClpP)and mediates the degradation of misfolded,damaged,and oxidized proteins,is essential for maintaining mitochondrial *** has been implicated in meiosis regulation,but its precise role is currently *** this study,we engineered an inducible male germ cell-specific knockout caseinolytic mitochondrial matrix peptidase X(Clpx^(cKO))mouse model to investigate the function of ClpX in *** found that disrupting Clpx in male mice induced germ cell apoptosis and led to an absence of sperm in the ***,it caused asynapsis of homologous chromosomes and impaired meiotic recombination,resulting in meiotic arrest in the zygotene-to-pachytene transition *** loss of ClpX compromised the double-strand break(DSB)repair machinery by markedly reducing the recruitment of DNA repair protein RAD51 homolog 1(RAD51)to DSB *** dysfunction may be due to an insufficient supply of energy from the aberrant mitochondria in Clpx^(cKO) spermatocytes,as discerned by electron ***,ubiquitination signals on chromosomes and the expression of oxidative phosphorylation subunits were both significantly attenuated in Clpx^(cKO) *** together,we propose that ClpX is essential for maintaining mitochondrial protein homeostasis and ensuring homologous chromosome pairing,synapsis,and recombination in spermatocytes during meiotic prophase I.

关键词： ClpX homologous chromosome meiosis mitochondrial recombination synapsis