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thermomechanical treatment of austempered ductile iron

China Foundry 2007年第4期4卷 304-309页

作者： A.A.Nofal H.Nasr El-din M.M.Ibrahim Central Metallurgical Research and Development Institute (CMRDI)CairoEgypt

The production of lightweight ferrous castings with increased strength properties became unavoidable facing the serious challenge of lighter aluminum and magnesium castings. The relatively new ferrous casting alloy ADI offers promising strength prospects, and the thermo-mechanical treatment of ductile iron may suggest a new route for production of thin-wall products. This work aims at studying the influence of thermomechanical treatment, either by ausforming just after quenching and before the onset of austempering reaction or by cold rolling after austempering. In the first part of this work, ausforming of ADI up to 25% reduction in height during a rolling operation was found to add a mechanical processing component compared to the conventional ADI heat treatment, thus increasing the rate of ausferrite formation and leading to a much finer and more homogeneous ausferrite product. The kinetics of ausferrite formation was studied using both metallographic as well as XRD-techniques. The effect of ausforming on the strength was quite dramatic （up to 70% and 50% increase in the yield and ultimate strength respectively）. A mechanism involving both a refined microstructural scale and an elevated dislocation density was suggested. Nickel is added to ADI to increase hardenability of thick section castings, while ausforming to higher degrees of deformation is necessary to alleviate the deleterious effect of alloy segregation on ductility. In the second part of this work, the influence of cold rolling （CR） on the mechanical properties and structural characteristics of ADI was investigated. The variation in properties was related to the amount of retained austenite （7~） and its mechanically induced transformation. In the course of tensile deformation of ADI, transformation induced plasticity （TRIP） takes place, indicated by the increase of the instantaneous value of strain-hardening exponent with tensile strain. The amount of retained austenite was found to decrease due to

关键词： ADI ausforming cold-rolling thermomechanical treatment transformation induced plasticity

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Effect of thermomechanical treatment on microstructure and properties of Cu-Cr-Zr-Ag alloy

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Rare Metals 2011年第6期30卷 650-656页

作者： XIE Haofeng MI Xujun HUANG Guojie GAO Baodong YIN Xiangqian LI Yanfeng State Key Laboratory of Nonferrous Metals and Processes General Research Institute for Nonferrous Metals Beijing 100088 China

The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920℃ for 1 h, cold drawing to 96% deformation, followed by aging at 400℃ for 3 h. TEM analysis revealed two kinds of finely dispersed precipitates of Cr and CuaZr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.

关键词： Cu-Cr-Zr-Ag alloy thermomechanical treatment microstructure tensile strength electrical conductivity

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Effect of thermomechanical treatment on microstructure and hardness behavior of AZ63 magnesium alloy

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Acta Metallurgica Sinica(English Letters) 2009年第6期22卷 401-407页

作者： H. Jafari M.H. Idris A. Ourdjini G. Payganeh Department of Materials Engineering Faculty of Mechanical EngineeringUniversiti Teknologi Malaysia Department of Materials Engineering Faculty of Mechanical EngineeringShahid Rajaee Teacher Training University Department of Materials Engineering Faculty of Mechanical Engineering Shahid Rajaee Teacher Training University

Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments （TMTs）. For the first TMT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃and 250 ℃ for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase （MglTA112） in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TMT, aging at 250 ℃ exhibited the best hardness values.

关键词： thermomechanical treatment Magnesium alloys Cold work Aging AZ63

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Manipulating Precipitation Through thermomechanical treatment to Control Corrosion Behavior of an Al–Cu–Mg Alloy

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Acta Metallurgica Sinica(English Letters) 2022年第9期35卷 1547-1558页

作者： Xiu-Rong Zhu Jun Wang Wei-Ning Shi Xue-Bing Liu Xin-Fang Zhang Hai-Fei Zhou Ningbo Branch Ordnance Science Institute of ChinaNingbo315103China School of Metallurgical and Ecological Engineering Metallurgical University of Science and Technology of BeijingBeijing100083China Zhejiang Electric Power Corporation Research Institute Hangzhou310000China

Controlling the precipitation through thermomechanical treatment is an important method to improve the corrosion resistance of Al–Cu–Mg alloys. In this study, the corrosion behaviors of Al–Cu–Mg alloys in the solution-treated state and retrogressiontreated state under cold rolling deformation and then natural aging were investigated. In the solution-treated series alloys, the cold-rolled deformation improved the resistance to intergranular corrosion by suppressing the precipitation of the S-phase on the grain boundaries. The increased pitting potential and corrosion potential were related to the increased concentration of solute atoms within the grain interiors and the eliminated S-phase on grain boundaries. In the retrogression-treated series alloys, the 30% cold rolling deformation stimulated the growth of the S-phase and transformed the S-phase distribution from discontinuous to continuous on the grain boundaries, thereby changing the pitting corrosion to the network corrosion morphology. The precipitation of the S-phase with large dimension within the grain interiors contributed to the decreased pitting potential and corrosion potential.

关键词： thermomechanical treatment Precipitation Intergranular corrosion Pitting corrosion

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Effect of thermomechanical treatment Temperature on Structure and Properties of CFB/M Ultra-High Strength Steel

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Journal of Iron and Steel Research International 2010年第4期17卷 66-72页

作者： XU Xue-xia BAI Bing-zhe LIU Dong-yua YUAN Ye Laboratory of Advanced Materials Department of Materials Science and Engineering Tsinghua UniversityBeijing 100084 China Hebei Electric Power Research Institute Shijiazhuang 050021 Hebei China School of Energy and Power Engineering North China Electric Power University Beijing 102206 China Northwest Electric Power Design Institute Xi’an 710075 Shaanxi China

Modified CCT diagram of carbide-flee bainite-martensite （CFB/M） ultra-high strength steel was established by applying controlled cooling of small samples. In addition, the influence of thermomechanical treatment tem- perature on the structure and properties was discussed. The experimental results showed that when deformed at 860℃ and below, ferrite transformation occurred due to strain. With the decrease of ausforming temperature, the quantity of ferrite increased and strength and toughness were deteriorated. Therefore, certain information was provided for optimizing technical parameter of ausforming process., firstly, the thermomechanical treatment temperature should not be lower than 860 ℃ in order to avoid ferrite formation induced by deformation; secondly, rapid cooling rate is also significant after deformation in order to avoid ferrite precipitation during subsequent cooling stage.

关键词： thermomechanical treatment carbide-free bainite/martensite (CFB/M) ultra-high strength steel

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Microstructure and mechanical properties of an Mg-4.0Sm-1.0Ca alloy during thermomechanical treatment

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Journal of Rare Earths 2016年第11期34卷 1134-1138页

作者：罗小萍房大庆李秋书柴跃生 College of Materials Science and Engineering Taiyuan University of Science and Technology

The microstructure and mechanical properties of an as-cast Mg-4.0Sm-1.0Ca alloy were investigated during thermome-chanical treatments consisting of hot extrusion, rolling, and aging at 473 K. Mg41Sm5 phases containing Ca and needle-like Mg2Ca phases formed in the Mg matrix, and the average grain size and elongation were 4.2μm and 27%, respectively, after hot extrusion, which implied an increase in ductility. In addition, after the rolling, the grain size was further refined, and the tensile strength in-creased to 293 MPa. A new precipitate Mg3Sm was found in the peak-aged Mg-4.0Sm-1.0Ca alloy and this alloy displayed the best mechanical properties, with a peak hardness of 83 HV and ultimate tensile strength of 313 MPa; these properties were attributed to grain refinement strengthening, solid solution strengthening, work hardening, and precipitation strengthening.

关键词： Mg-Sm-Ca alloy thermomechanical treatment microstructure mechanical properties rare earths

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Effects of thermomechanical treatment on the Mechanical Properties and Microstructures of 6013 Alloy

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Journal of Wuhan University of Technology(Materials Science) 2009年第2期24卷 198-201页

作者：何立子 Key Lab of Electromagnetic Processing of Materials Ministry of Education Northeastern University

The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy （TEM）. The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness （HVmax） increases, the time to HV shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment.

关键词： 6013 alloy thermomechanical treatment aging dislocation

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Properties improvement and microstructure changes during thermomechanical treatment in sintered Cu-Au alloy

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Transactions of Nonferrous Metals Society of China 2014年第2期24卷 431-440页

作者： Ivana MARKOVIC Svetlana NESTOROVIC Desimir MARKOVIC Dragoslav GUSKOVIC Technical faculty in Bor University of BelgradeVJ 12 19210 Bor Serbia

The changes in hardness, microhardness, electrical conductivity and microstructure of the sintered Cu-4%Au （mole fraction） alloy during thermomechanical treatment were studied. Following the primary strain hardening, an annealing of rolled alloy in the temperature range of 60-350 ℃ provided additional strengthening due to the anneal hardening effect. An increase in properties took place in two stages, and the best combination of properties was achieved in the alloy pre-rolled with 40% reduction after annealing at 260 ℃. Significant microstructural changes followed the changes of properties in the course of the thermomechanical treatment.

关键词： Cu-Au alloys anneal hardening thermomechanical treatment hardness microhardness electrical conductivity

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Microstructure characterization and mechanical properties of TC4-DT titanium alloy after thermomechanical treatment

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Transactions of Nonferrous Metals Society of China 2014年第3期24卷 682-689页

作者：彭小娜郭鸿镇石志峰秦春赵张龙西北工业大学材料学院西安710072

Influence of thermomechanical treatments （mill annealing, duplex annealing, solution treatment plus aging and triple annealing） on microstructures and mechanical properties of TC4-DT titanium alloy was investigated. Results showed that thermomechanical treatments had a significant influence on the microstructure parameters and higher annealing and aging temperature and lower cooling rate led to the decrease of the volume fraction of primaryαand the size of prior-βand the increase of the width of grain boundary αand secondary α. The highest strength was obtained by solution treatment and aging due to a large amount of transformedβand finer grain boundaryαand secondaryαat the expense of slight decrease of elongation and the ultimate strength, yield strength, elongation, reduction of area were 1100 MPa, 1030 MPa, 13%and 53%separately. A good combination of strength and ductility has been obtained by duplex annealing with the above values 940 MPa, 887.5 MPa, 15%and 51%respectively. Analysis between microstructure parameters and tensile properties showed that with the volume fraction of transformedβphase and the prior-βgrain size increasing, the ultimate strength, yield strength and reduction of area increased, but the elongation decreased. While the width of grain boundary α and secondary α showed a contrary effect on the tensile properties. Elimination of grain boundaryαas well as small prior-βgrain size can also improve ductility.

关键词： TC4-DT titanium alloy thermomechanical treatment microstructures tensile properties

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Effect of thermomechanical cyclic quenching and tempering treatments on microstructure,mechanical and electrochemical properties of AISI 1345 steel

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International Journal of Minerals,Metallurgy and Materials 2021年第4期28卷 688-698页

作者： Muhammad Arslan Hafeez Ameeq Farooq Kaab Bin Tayyab and Muhammad Adnan Arshad School of Civil and Environmental Engineering National University of Sciences and TechnologyIslamabad 44000Pakistan Department of Metallurgy&Materials Engineering University of the Punjab54590 LahorePakistan

thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction *** effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was *** samples heated to 1050℃,rolled,quenched to room temperature,and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1,TMCT-2,and TMCT-3 samples,*** analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes(2.8–7.9μm).Among all the tested samples,TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40%in tensile strength and reduced 34%elongation compared with the non-treated *** results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51%improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated *** electrochemical properties were analyzed in 0.1 M NaHCO_(3) solution by potentiodynamic polarization and electrochemical impedance *** a result of TMCT,the minimum corrosion rate was 0.272 mm/a,which was twenty times less than that of the nontreated *** impedance results showed the barrier film mechanism,which was confirmed by the polarization results as the current density decreased.

关键词： thermomechanical treatment cyclic heat-treatment nanoindentation potentiodynamic polarization electrochemical impedance spectroscopy

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