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Atomic insights into heterogeneous nucleation and growth kinetics of Al on tib_(2) particles in undercooled Al-5Ti-1B melt

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Journal of Materials Science & Technology 2023年第25期156卷 72-82页

作者： Jing Feng Yanfeng Han Xiaocang Han Xiaodong Wang Shuangxi Song Baode Sun Mingwei Chen Pan Liu Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming State Key Laboratory of Metal Matrix Composites School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Department of Materials Science and Engineering Johns Hopkin UniversityBaltimoreMD 21218USA

Titanium diboride(tib_(2))is an effective grain refiner of Al alloys in the industry that facilitates casting processes by forming uniformly refined *** our understanding of the underlying refinement mechanisms has advanced,the atomic kinetics of heterogeneous nucleation of Al on tib2 remains ***,we report atomic-scale observations of the heterogeneous nucleation and growth kinetics of Al on self-formed tib_(2) particles by in situ heating of undercooled Al-5Ti-1B *** demonstrate that an ordered Al monolayer forms on the Ti-terminated{0001}tib_(2) surface;then,the surrounding Al atoms are initiated to form an island-shaped Al nucleus with face-centered cubic{111}stacking without the assistance of a Ti-rich buffer *** interfacial lattice mismatch between{111}Al and{0001}tib_(2) causes remarkable out-of-plane strain that decreases gradually with Al nucleus layers increasing to 6 atomic *** elastic strain energy originating from this interfacial strain increases the free energy of the Al/tib2 heterostructure,hence impeding the rapid growth of the Al *** found that tib2 particles stabilize the Al nuclei rather than activating their free growth into grains when the experimental undercoolingΔT is lower than the onset undercoolingΔT fg in Greer's free growth *** findings provide an atomic-scale physical image of the heterogeneous nucleation and growth mechanisms of Al with inoculator participation and elucidate the strain-dependent growth kinetics of Al nuclei.

关键词： In situ tem Heterogeneous nucleation Lattice strain Aluminum tib2 particles

Kinetic behaviour of tib particles in Al melt and their effect on grain refinement of aluminium alloys

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Transactions of Nonferrous Metals Society of China 2020年第8期30卷 2035-2044页

作者： Li-li ZHANG Hong-xiang JIANG Jie HE Jiu-zhou ZHAO Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

Solidification experiments were carried out to investigate the kinetic behaviour of tib2 particles in Al melt and their effect on the grain refinement of commercially-pure Al.A model was proposed to describe the kinetic behaviour of tib2 particles during the whole process from the addition of tib2 to the melt to the freezing of the *** results indicate that tib2 particles are not stable in Al *** may dissolve and coarsen during the holding period and grow during the cooling period of the *** kinetic behaviour of tib2 particles in the melt has a great influence on their number density and the grain *** Ti addition can suppress the dissolution,Ostwald ripening and growth behaviours of tib2 particles.

关键词： tib2 particles kinetic behaviour grain refinement aluminium alloy

Microstructural evolution of copper-titanium alloy during in-situ formation of tib_2 particles

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Transactions of Nonferrous Metals Society of China 2013年第10期23卷 2994-3001页

作者： M.SOBHANI H.ARABI A.MIRHABIBI R.M.D.BRYDSON Center of Excellence for Advanced Materials and Processing School of Metallurgy and Materials Engineering Iran University of Science and Technology Center of Excellence for Ceramic Materials in Energy and Environmental Applications Iran University of Science and Technology Institute for Materials Research University of Leeds

Bulk Cu-Ti alloy reinforced by tib2 nano particles was prepared using in-situ reaction between Cu 3.4%Ti and Cu-0.7%B master alloys along with rapid solidification and subsequent heat treatment for 1-10 h at 900 ℃. High-resolution transmission electron microscopy （HRTEM） characterization showed that primary tib2 nano particles and tib whiskers were formed by in-situ reaction between Ti and B in the liquid copper. The formation of tib whiskers within the melt led to coarsening of tib2 particles. Primary tib2 particles were dispersed along the grain boundaries and hindered grain growth at high temperature, while the secondary tib2 particles were formed during heat treatment of the alloy by diffusion reaction of solute titanium and boron inside the grains. Electrical conductivity and hardness of the composite were evaluated during heat treatment. The results indicated that the formation of secondary tib2 particles in the matrix caused a delay in hardness reduction at high temperature. The electrical conductivity and hardness increased up to 8 h of heat treatment and reached 33.5% IACS and HV 158, respectively.

关键词： in-situ reaction tib whiskers tib2 particles Cu-Ti alloy composite

Microstructure, mechanical properties and wear behaviour of Zn-Al-Cu-tib_2 in situ composites

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Transactions of Nonferrous Metals Society of China 2015年第1期25卷 103-111页

作者：陈飞王同敏陈宗宁毛丰韩强曹志强大连理工大学材料科学与工程学院大连116024

Zn-Al-Cu-tib2（ZA27-tib2） in situ composites were fabricated via reactions between molten aluminum and mixed halide salts（K2TiF6 and KBF4） at temperature of 875 °C. The microstructure, mechanical properties and wear behavior of the composites were investigated. Microstructure analysis shows that fine and clean tib2 particles distribute uniformly through the matrix. The mechanical properties of the composites increase with the increase in tib2 content. As tib2 content increases to 5%（mass fraction）, an improvement of HB 18 in hardness and 49 MPa in ultimate tensile strength（UTS） is achieved. The overall results reveal that the composites possess low friction coefficients and the wear rate is reduced from 5.9×10-3 to 1.3×10-3 mm3/m after incorporating 5% tib2. Friction coefficient and worn surface analysis indicate that there is a change in the wear mechanism in the initial stage of wear test after introducing in situ tib2 particles into the matrix.

关键词： in situ composites tib2 particles friction coefficient wear rate mechanical properties