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您的检索式：作者名="Taha Mattar"
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| 1 | Effect of cooling rate and composition on microstructure and mechanical properties of ultrahigh-strength steels显示文摘The influence of cooling rate on the microstructure and mechanical properties of two new ultrahigh-strength steels(UHSSs)with different levels of C,Cr and Ni has been evaluated for the as-cooled and untempered condition.One UHSS had higher contents of C and Cr,while the other one had a higher Ni content.On the basis of dilatation curves,microstructures,macrohardness and microhardness,continuous cooling transformation diagrams were constructed as a guide to heat treatment possibilities.Cooling rates(CRs)of 60,1 and 0.01°C/s were selected for more detailed investigations.Microstructural characterization was made by laser scanning confocal microscopy,field emission scanning electron microscopy combined with electron backscatter diffraction,electron probe microanalysis and X-ray diffraction.Mechanical properties were characterized using macrohardness,tensile and Charpy V-notch impact tests.UHSS with the higher C and Cr contents showed lower transformation temperatures and slower bainite formation kinetics than that with the higher Ni content.Higher cooling rates led to lower volume fractions and carbon contents of retained austenite together with finer prior austenite grain size,as well as effective final grain size and lath size.These changes were accompanied by higher yield and tensile strengths.The best combinations of strength and toughness were obtained with martensitic microstructures and by avoiding the formation of granular bainite accompanied by proeutectoid carbides at low CR.For the cooling rates studied,UHSS with the higher C and Cr contents showed the higher hardness and strength but at the cost of toughness. | Mohammed Ali David Porter Jukka Komi Mamdouh Eissa Hoda El Faramawy Taha Mattar | 2019 | Journal of Iron and Steel Research(International)2019，26，12： | 1 |
| 2 | Effect of Tempcore Processing on Mitigating Problems of Tramp Elements in Low C Steel Produced from Recycled Material显示文摘The effect of tramp elements in the steel was intensively studied.It was found that the solubility of tramp elements decreased as the temperature decreased under normal cooling conditions.The tramp elements(Cu,Pb,and Sn)diffused toward the grain boundaries,and intermetallic compounds or rich phases which have low melting points were formed,causing reduction in ductility and failure during the bending test.Rebars with Cu content which were left to air cooling after the last step showed drop in elongation,up to 32%.On contrast,the samples with high percentage of tramp elements(Cu,Pb,and Sn)in the billet,which were rolled and subjected to Tempcore process,did not show drop in elongation or failure in bending test(especially for rebar with diameter less than 32mm);however,copper must be less than 0.35mass%to prevent the precipitation of Cu-rich zones of critical size in 32 mm.When quenching was applied,the tramp elements remained in the interstitial supersaturated solid solution positions inside the grains and would not have the chance to diffuse and form precipitates,hindering the copper precipitates from reaching the critical size necessary for impairing the properties.This would hinder the occurrence of the harmful effect of the tramp elements on the elongation or the hot shortness after rolling. | Ahmed RAMADAN A.Y.SHASH I.S.EL-MAHALLAWI D.SENK Taha MATTAR | 2015 | Journal of Iron and Steel Research(International)2015，22，7： | 0 |
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