A device based on a high pressure die-casting(HPDC) machine was constructed,with a capacity to produce thixo-casts from steel.After inductive heating to the required semi-solid temperature range,the samples were trans...A device based on a high pressure die-casting(HPDC) machine was constructed,with a capacity to produce thixo-casts from steel.After inductive heating to the required semi-solid temperature range,the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die.Bearing steel 100Cr6(after forging) was used as the feedstock material.The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 μm and 8 μm.Differential scanning calorimetry(DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 ?C which was attributed to about 45% of a liquid phase.With such technological parameters after the semi-solid processing the microstructure consisted of globular grains of size from 15 μm to 40 μm.The microstructure of globules indicated predominant presence of martensite(about 76% volume fraction) with residual austenite between plates.X-ray analysis confirmed that the thixo-cast samples contain mainly martensite and residual austenite.The hardness of the initial forged sample was HRC 27 and after the thixoforming process it was HRC 60,which confirms the presence of martensite and carbides.The thixo-casts were subjected to low tempering,at temperature of 150 °C for a period of 2 h,in order to remove stresses created during the process of thixoforming and to increase plasticity.The hardness after tempering was HRC 62.3.Additionally,in order to identify phases present in the thixo-casts,transmission electron microscopy(TEM) was carried out.展开更多
In this paper, the results of the investigation of the morphology and phase composition of the oxide layers formed on the surface of the 1H18N9T acid proof steel foil by confocal Raman micro-spectroscopy with optical ...In this paper, the results of the investigation of the morphology and phase composition of the oxide layers formed on the surface of the 1H18N9T acid proof steel foil by confocal Raman micro-spectroscopy with optical microscopy, SEM, XRD and TEM-EDS-SADP are presented. The foil oxidation was performed by thermo-programmed heating up to 823, 1023 or 1113 K and next annealing at the final temperatures in the air flow for 48 h, 4 h and 4 h, respectively. The great advantages of the use of the Raman spectroscopy for the phase determining in the oxide layers on the acid proof steel foil are shown. Moreover the possibility of applying the optical microscopy for investigation of the surface morphology of both the initial steel foil and the oxide layers is pointed out.展开更多
文摘A device based on a high pressure die-casting(HPDC) machine was constructed,with a capacity to produce thixo-casts from steel.After inductive heating to the required semi-solid temperature range,the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die.Bearing steel 100Cr6(after forging) was used as the feedstock material.The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 μm and 8 μm.Differential scanning calorimetry(DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 ?C which was attributed to about 45% of a liquid phase.With such technological parameters after the semi-solid processing the microstructure consisted of globular grains of size from 15 μm to 40 μm.The microstructure of globules indicated predominant presence of martensite(about 76% volume fraction) with residual austenite between plates.X-ray analysis confirmed that the thixo-cast samples contain mainly martensite and residual austenite.The hardness of the initial forged sample was HRC 27 and after the thixoforming process it was HRC 60,which confirms the presence of martensite and carbides.The thixo-casts were subjected to low tempering,at temperature of 150 °C for a period of 2 h,in order to remove stresses created during the process of thixoforming and to increase plasticity.The hardness after tempering was HRC 62.3.Additionally,in order to identify phases present in the thixo-casts,transmission electron microscopy(TEM) was carried out.
基金the financial support by the European Regional Development Fund under the Innovate Economy Operational Program 2007-2013,POIG.01.01.02-12-112/09 project.
文摘In this paper, the results of the investigation of the morphology and phase composition of the oxide layers formed on the surface of the 1H18N9T acid proof steel foil by confocal Raman micro-spectroscopy with optical microscopy, SEM, XRD and TEM-EDS-SADP are presented. The foil oxidation was performed by thermo-programmed heating up to 823, 1023 or 1113 K and next annealing at the final temperatures in the air flow for 48 h, 4 h and 4 h, respectively. The great advantages of the use of the Raman spectroscopy for the phase determining in the oxide layers on the acid proof steel foil are shown. Moreover the possibility of applying the optical microscopy for investigation of the surface morphology of both the initial steel foil and the oxide layers is pointed out.
