Prof. Dr. YongKun Li
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Academic Career Length
9Years (2018-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications1 September 2021 in Journal of Materials Research and Technology
Journal Article
YongKun LiSXShuaiying Xi
Shuaiying Xi
GMGuodong Ma
Guodong Ma
YXYing Xiao
Ying Xiao
LLLu Li
Lu Li
YJYehua Jiang
Yehua Jiang
+3
Journal Article
LZLingzhi Zhang
Lingzhi ZhangYongKun LiRZRongfeng Zhou
Rongfeng ZhouXWXiao Wang
Xiao WangQWQiansi Wang
Qiansi WangBXBin Xu
Bin Xu +2
In order to explore the mechanism of the influence of Sn contents on the relevant properties of Cu–Sn alloys, the structure, elasticity, electronic, and thermal properties of Cu–Sn alloys doped with different proportions of Sn (3.125 at%, 6.25 at%, and 9.375 at%) were established using the first-principles calculation based on density functional theory. Firstly, their lattice constants and Sn concentration comply with Vegard’s Law. From the mixing enthalpy, it can be seen that Sn atoms can be firmly dissolved in the Cu matrix, and the structure is most stable when the Sn content is 3.125 at%. In addition, the introduction of mismatch strain characterized their solid solution strengthening effect. The elastic and electronic properties showed that when the Sn content is 6.25 at%, the Cu–Sn alloy has the best plasticity and the highest elastic anisotropy; when the Sn content is 3.125 at%, the Cu–Sn alloy is the most stable and has stronger bulk and shear modulus, which was mainly due to a stronger Cu-Cu covalent bond. Finally, the Debye temperature, thermal conductivity, and melting point were calculated. It is estimated that the thermal conductivity of Cu–Sn alloy is relatively good when the Sn content is low.
Journal Article
GBGeng Baoyu
Geng BaoyuRZRongfeng Zhou
Rongfeng ZhouLLLu Li
Lu LiHLHaiyang Lv
Haiyang LvYongKun LiYJYeHua Jiang
YeHua Jiang +1
In this work, an electric current pulse (ECP) of 500A was applied on a hypereutectic high chromium cast iron (HHCCI) melt before it began to solidify, and the effect of ECP on primary carbides was investigated. The characteristics of the primary carbides were analyzed by X-ray diffraction (XRD), electron probe micro-analyzer (EPMA), transmission electron microscopy (TEM), micro hardness tester, and other techniques. The results showed that ECP not only refined the primary (Cr, Fe)7C3 carbides, but also decreased the average content of Cr in the primary carbides. At the same time, the average value of micro hardness of the primary carbides increased by about 84 Kgf/mm2, which contradicts existing knowledge that hardness increases with an increase in Cr content. XRD analysis showed that the crystal structure of the primary carbides did not change. The results of EPMA indicated that the Cr/Fe ratio gradually decreased from the center to the edges of the carbide particles. Further investigation revealed that the uneven distribution of elements caused by ECP led to an increase in defects (including twins, antiphase boundaries, and dislocations). This increase in defect density is the main reason for the increase in micro hardness instead of the expected decrease. The mechanism of the change in primary carbides was analyzed in detail in this paper, which has provided a new method for the refinement of primary carbides and for improving the properties of primary carbides.
4 January 2024 in Metals and Materials International
Journal Article
LXLingzhi Xie
Lingzhi Xie
YongKun LiRZRongfeng Zhou
Rongfeng ZhouZLZhaoqiang Li
Zhaoqiang Li
QWQiansi Wang
Qiansi Wang
BXBin Xu
Bin Xu
+2
Journal Article
YongKun LiRZRongfeng Zhou
Rongfeng ZhouLLLu Li
Lu LiHXHan Xiao
Han XiaoYJYeHua Jiang
YeHua JiangSemi-solid ZCuSn10P1 alloy slurry was fabricated by a novel enclosed cooling slope channel (ECSC). The influence of pouring length of ECSC on the microstructures of ZCuSn10P1 alloy semi-solid slurry was studied with an optical microscope an optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). Liquid squeeze casting and semi-solid squeeze casting were performed under the same forming conditions, and the microstructure and properties were compared. The results show that primary α-Cu phase gradually evolved from dendrites to worm-like or equiaxed grains under the chilling action of the inner wall of the ECSC. The mass fraction of tin in the primary α-Cu phase increased from 5.85 to 6.46 after the ECSC process, and intergranular segregation was effectively suppressed. The finest microstructure can be obtained at 300 mm pouring length of ECSC; the equivalent diameter is 46.6 μm and its shape factor is 0.73. The average ultimate tensile strength and average elongation of semi-solid squeeze casting ZCuSn10P1 alloy reached 417 MPa and 12.6%, which were improved by 22% and 93%, respectively, as compared to that of liquid squeeze casting.
Journal Article
ZLZhaoqiang Li
Zhaoqiang LiYongKun LiRZRongfeng Zhou
Rongfeng ZhouLXLingzhi Xie
Lingzhi XieQWQiansi Wang
Qiansi WangBXBin Xu
Bin Xu +2
In this study, an enclosed cooling slope channel (ECSC) was used to produce a semi-solid slurry of the 7075 aluminum alloy. The effects of the pouring temperature and the rate of cooling water on the microstructure of the semi-solid slurry were studied. The microstructure, solidification behavior, mechanical properties, and fracture mechanism of rheological squeeze casting (Rheo-SC) and liquid squeeze casting (LSC) samples were compared. The results indicate that lowering the pouring temperature and increasing the rate of cooling water can refine the crystals of the semi-solid slurry. The best process is a pouring temperature of 670 °C and a rate of cooling water of 200 L/h. The microstructure of the LSC samples was made up of coarse dendritic crystals, but the microstructure of the Rheo-SC samples was made up of almost spherical primary α1-Al and refined secondary α2-Al under this method. The ultimate tensile strength, yield strength, and elongation of the Rheo-SC samples were 238 MPa, 151 MPa, and 5.2%, respectively, which were 10%, 10.5%, and 44.4% higher than those of the LSC sample. The key factor contributing to the increased performance of the Rheo-SC samples is the combination of decreased casting flaws, strengthened grain refinement, and improved segregation.
About Me
Li Yongkun, Ph.D. / Postdoctoral, associate professor at Kunming University of Science and Technology, is a young top-notch talent under the "Xingdian Talent" program of Yunnan Province, China. Devoted to the research on the solidification and forming control of non-ferrous metals, focusing on the refinement of grains, forming control, and strengthening and toughening mechanisms of non-ferrous metals like aluminum, copper, and titanium.
He has presided over projects such as the National Science Foundation of China for Young Scholars, the China Postdoctoral Science Foundation General Project, the Yunnan Province "Xingdian Talent Support Program" Youth Talent Project, the Yunnan Province Applied Foundation Enterprise Joint Special Project, and the Yunnan Province Applied Foundation Youth Projec. He has also participated in research on more than ten projects including the National Natural Science Foundation of China, Major Science and Technology Projects of Yunnan Province, International Joint Projects of Yunnan Province, and general projects of the Yunnan Provincial Department of Science and Technology. As the first author, more than 20 academic papers such as SCI and EI have been published in academic journals such as Materials Characterization, Journal of Materials Research and Technology, and JMR. Four national authorized invention patents and eight utility model patents have been obtained. Published a monograph titled "Semi-solid Rheological Forming of Tin Bronze".