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Grain Size Distribution and Interfacial Heat Transfer Coefficient during Solidification of Magnesium Alloys Using High Pressure Die Casting Process

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Journal of materials Science & Technology 2018年第2期34卷 324-334页

作者： P. Sharifi J. Jamali K. Sadayappan J.T. Wood Western University London Ontario Canada canmet materials Hamilton ON Canada

The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASTTM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. The simulation results were used to estimate the centerline cooling curve at various locations through the casting. The centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. The effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. The grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. The prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.

关键词： High pressure die casting Grain size lnterfacial heat transfer coefficient Solidification of magnesium alloys Process parameters

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Mixed graphite cast iron for automotive exhaust component applications

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China Foundry 2017年第6期14卷 519-524页

作者： De-lin Li canmet materials Natural Resources CanadaHamiltonONCanada

Both spheroidal graphite iron and compacted graphite iron are used in the automotive industry. A recently proposed mixed graphite iron exhibits a microstructure between the conventional spheroidal graphite iron and compacted graphite iron. Evaluation results clearly indicate the suitability and benefits of mixed graphite iron for exhaust component applications with respect to casting, machining, mechanical, thermophysical, oxidation, and thermal fatigue properties. A new ASTM standard specification(A1095) has been created for compacted, mixed, and spheroidal graphite silicon-molybdenum iron castings. This paper attempts to outline the latest progress in mixed graphite iron published.

关键词： SiMo iron spheroidal graphite compacted graphite mixed graphite exhaust components brittleness at medium temperature thermal fatigue cycles

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Microstructure,texture and mechanical behavior characterization of hot forged cast ZK60 magnesium alloy

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Journal of materials Science & Technology 2017年第9期33卷 907-918页

作者： S.M.H.Karparvarfard S.K.Shaha S.B.Behravesh H.Jahed B.W.Williams Department of Mechanical & Mechatronics Engineering University of Waterloo canmet materials Natural Resources Canada

structure with a significant reduction in casting porosity, while the texture changed to sharp basaMeasured mechanical properties of the forged alloy showed that strength did not change, howductility improved by 75%. The analysis of the fracture surface of the forged alloy under tension rea ductile fracture with dimple morphology, while the as-cast alloy displayed a brittle fracture with pores. This demonstrated that the reduction of casting defects and dendritic morphology, as well evolution of recrystallized grains, enhanced ductility, while partial dynamic recrystallization throuforging process resulted in only marginal modification of strength in the forged condition.. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of materials SciTechno

关键词： Magnesium Forging Ductility Texture Recrystallization

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A critical examination of robustness and generalizability of machine learning prediction of materials properties

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npj Computational materials 2023年第1期9卷 1787-1795页

作者： Kangming Li Brian DeCost Kamal Choudhary Michael Greenwood Jason Hattrick-Simpers Department of materials Science and Engineering University of Toronto27 King’s College CirTorontoONCanada Material Measurement Laboratory National Institute of Standards and Technology100 Bureau DrGaithersburgMDUSA Theiss Research La JollaCA 92037USA canmet materials Natural Resources Canada183 Longwood Road southHamiltonONCanada

Recent advances in machine learning(ML)have led to substantial performance improvement in material database benchmarks,but an excellent benchmark score may not imply good generalization performance.Here we show that ML models trained on materials Project 2018 can have severely degraded performance on new compounds in materials Project 2021 due to the distribution shift.We discuss how to foresee the issue with a few simple tools.Firstly,the uniform manifold approximation and projection(UMAP)can be used to investigate the relation between the training and test data within the feature space.Secondly,the disagreement between multiple ML models on the test data can illuminate out-of-distribution samples.We demonstrate that the UMAP-guided and query by committee acquisition strategies can greatly improve prediction accuracy by adding only 1%of the test data.We believe this work provides valuable insights for building databases and models that enable better robustness and generalizability.

关键词： prediction adding critical

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Repairing of exit-hole in friction-stir-spot welded joints for 2024-T4 aluminum alloy by resistance welding

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International Journal of Minerals,Metallurgy and materials 2023年第4期30卷 660-669页

作者： Lipeng Deng Pengliang Niu Liming Ke Jinhe Liu Jidong Kang School of Aeronautical Manufacturing and Engineering Nanchang Hangkong UniversityNanchang 330063China School of Material Science and Engineering Northwestern Polytechnical UniversityXi’an 710072China canmet materials Natural Resources Canada183 Longwood Road SouthHamiltonON L8P0A5Canada

The exit-hole in friction stir spot welded(FSSWed) 2024-T4 aluminum alloy joints was successfully repaired by using a three-phase secondary rectification resistance spot welding machine, which is termed as filling exit-hole based on resistance welding(FEBRW). The filling dynamic behavior of force was recorded by a device monitoring. Optical microscope(OM), electron backscatter diffraction(EBSD), and tensile shear tests and finite element modelling were conducted to investigate the repairing stages and bonding mechanisms of the repaired joints in detail. Results showed that exit-hole was completely filled and repaired experiencing three stages. Metallurgical bonding was achieved between plug and exit-hole wall in two forms, including melting bonding in the middle of the joints and partial diffusion bonding on both the upper and bottom of the joints. The highest tensile shear strength of the repaired joints was 7.43 kN, which was 36.3% higher than that of the as welded joints. Resistance welding paves an efficient way to repair the exit-hole in FSSWed joints.

关键词： resistance welding exit-hole repairing bonding mechanisms

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Enhancement of the nickel converter slag-cleaning operation with the addition of spent potlining

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International Journal of Minerals,Metallurgy and materials 2018年第8期25卷 881-891页

作者： Dawei Yu Kinnor Chattopadhyay School of Metallurgy and Environment Central South University canmet MINING Natural Resources Canada Process Metallurgy & Modelling Group Department of Materials Science and EngineeringUniversity of Toronto

The slag cleaning(or matte settling) process was experimentally investigated at 1573 K using a fayalitic nickel converter slag containing spinel and matte/alloy particles.The addition of various amounts of spent potlining(SPL) was studied in terms of its influence on matte settling and the overall metal recoveries.The slags produced were characterized by scanning electron microscopy,energy-dispersive spectroscopy,and wet chemical analysis using inductively coupled plasma optical emission spectrometry.The presence of solid spinel particles in the molten slag hindered coalescence and settling of matte/alloy droplets.Matte settling was effectively promoted with the addition of as little as 2 wt% SPL because of the reduction of spinel by the carbonaceous component of the SPL.The reduced viscosity of the molten slag in the presence of SPL also contributed to the accelerated matte settling.Greater metal recoveries were achieved with larger amounts of added SPL.Fast reduction of the molten slag at 1573 K promoted the formation of highly dispersed metal particles/clusters via accelerated nucleation in the molten slag,which increased the overall slag viscosity.This increase in viscosity,when combined with rapid gas evolution from accelerated reduction reactions,led to slag foaming.

关键词： converter slag spent potlining matte nickel matte settling fayalite

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超细晶钒微合金化双相钢性能

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钢铁钒钛 2017年第4期38卷 94-104页

作者： C.P.Scott F.Fazeli B.Shalchi I.Pushkareva 杨雄飞 canmet materials Natural Resources Canada

研究了钒微合金化对高强双相钢微观组织及性能的影响。与Fe-0.186C-1.5Mn-0.3Si-0.008N参照钢相比,加入0.14%V带来如下效果:(1)在冷轧及退火状态铁素体晶粒高度细化;(2)严重推迟在连续退火过程中铁素体向奥氏体转变的初始动力学;(3)慢... 详细信息

研究了钒微合金化对高强双相钢微观组织及性能的影响。与Fe-0.186C-1.5Mn-0.3Si-0.008N参照钢相比,加入0.14%V带来如下效果:(1)在冷轧及退火状态铁素体晶粒高度细化;(2)严重推迟在连续退火过程中铁素体向奥氏体转变的初始动力学;(3)慢冷条件下铁素体开始转变温度稍微提高,但珠光体和贝氏体转变被抑制,导致淬透性提高;(4)在临界退火温度≤740℃时观察到未溶渗碳体;(5)750℃/180 s退火后铁素体相中发现大量V(C,N)析出(平均直径7.4 nm),而马氏体(奥氏体)中析出物稀少,尺寸更大(平均直径13.4 nm);(6)不含钒参照钢抗拉强度随马氏体体积分数增量为~16 MPa/%,而含钒钢由于晶粒细化和铁素体选择强化,强度随马氏体含量变化增量相当低(~4 MPa/%),在马氏体体积分数>45%变软。

关键词： DP钢 AHSS 超细晶钒微合金化

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Chemical Potential of Vacancies in Metal Crystals

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材料科学与工程学报 2000年第Z1期20卷 109-111页

作者： SUN Jun State Key Laboratory for Mechanical Behavior of materials School of materials Science and Engineering Xi'an Jiaotong University Xi'an 710049 China Materials Technology Laboratory MTL/CANMET Ottawa Canada

In this paper, a concept, the chemical potential of vacancies in metal crystals, has been derived from the partial mole free energy of vacancies based on a model of an atom-vacancy binary solution.For a pure metal crystal containing the mole concentration of vacancies, Cv and it's value in thermal equilibrium,C0, at temperature T the chemical potential can be expressed respectively as: μ v(Cv)=RT[1+1n(C√Co)]and μ v (Co)=RT The second term in μ v(Cv) is the chemical potential of the vacancies referred to the standardstate concentration given by J. P. Hirth [1] and first term is the standard-state one presented in this paper.

关键词： chemical potential thermal equilibrium temperature T metal crystal free energy

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EFFECT OF RARE EARTH ADDITIONS ON FRACTURE PROPERTIES OF 2.25Cr-1Mo STEELS

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Acta Metallurgica Sinica(English Letters) 1989年第1期2卷 63-68页

作者： W.R.TYSON B.FAUCHER Physical Metallurgy Research Laboratories CANMETOttawaCanada

The inclusion parameters,fracture surface morphology and void growth characteristics of ten- sile and fracture toughness specimens of 2.25Cr-1Mo steels with and without rare-earth (RE)additions have been investigated by quantitative metaltography(QTM),scanning elec- tron microscopy(SEM)and energy dispersive spectroscopy(EDS).There is a substantially higher density of inclusions in the RE-treated steel,which has lower values of fracture proper- ties including critical values of COD and J integral(δ_c and J_(IC)),fracture strain(ε_f) and Charpy V-notch energy(CVN).The fracture surface of the RE-treated steel comprises equiaxed dimples of diameters comparable with its inclusion spacing,whereas for the non-RE-treated steels,a wide range of dimple sizes is found with average diameter much smaller than the corresponding inclusion spacing.The investigation indicates that the lower values of fracture properties for the steel with RE at room temperature may be ascribed to its large content of RE-containing inclusions.

关键词： Cr-Mo steel fracture properties inclusion parameters fracture morphology

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Mineralogical Characterization of Sieved and Un-Sieved Samples

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Journal of Minerals and materials Characterization and Engineering 2014年第1期2卷 40-48页

作者： Rolando Lastra William Petruk NRCan-canmet Mining Ottawa Canada

Mineralogical characterization applied to mineral processing is now widespread. The first step for a mineralogi- cal characterization study is usually size fractionation. Preparation of polished sections is done on size fractions to reduce complications in making representative cross sections of particles with large size differences. A sample is commonly fractionated into five or six size intervals. The drawback of this procedure is that it makes liberation studies more expensive, because one sample actually produces five or six sub-samples that need to be studied, i.e. one from each size interval. Thus to reduce cost of liberation studies, it would be desirable to study the un-sized sample. This paper provides a comparative liberation study of a set of samples both using size fractions and using the un-sized samples. The samples studied are the feed, the concentrate and the tails of a lead rougher flotation circuit. The results consistently show significant differences between the sized and the un-sized samples. Nevertheless, the results indicate that un-corrected liberation data from un-sized samples can be used for comparative studies that involve several related samples. Thus, it is possible to improve (or further understand) a concentrator circuit by using mineralogical data from un-sized samples around such circuit.

关键词： Mineral Liberation Sieved Un-Sieved

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