S K Ghosh
,
P Mallick
,
P P Chattopadhyay
钢铁研究学报(英文版)
Abstract： The effects of cold deformation on the formation of strain induced α′ martensite and mechanical properties of an austenitic stainless steel have been examined. X-ray diffraction analysis has revealed that 30% and 40% cold rolling have resulted in the formation of 24% and 315% martensite respectively. Microstructural investigation has demonstrated that the formation of martensite is enhanced with increase in the percent deformation at 0 ℃. Investigation of mechanical properties reveals that hardness, yield strength and tensile strength values increase where as percent elongation drops with increasing deformation. The fractographic observation corroborates the tensile results. Examination of sub-surface at the fractured end of the tensile sample manifests that void/microcrack nucleation occurs in the interfacial regions of the martensite phase as well as at the austenite-martensite interface.
关键词:
Key words: austenitic stainless steel
,
cold deformation
,
martensite
,
mechanical property
JIANG Hai-tao
,
DING Wei
,
TANG Di
,
HUANG Wei
钢铁研究学报(英文版)
Mechanical properties and microstructure in high strength hot dip galvanizing TRIP steel were investigated by optical microscope (OM), transmission electron microscope (TEM), X-ray diffraction (XRD), dilatometry and mechanical testing. On the heat treatment process of different intercritical annealing (IA) temperatures, isothermal bainitic transformation (IBT) temperatures and IBT time, this steel shows excellent mechanical properties with tensile strength over 780 MPa and elongation more than 22%. IBT time is a crucial factor in determining the mechanical properties as it confirms the bainite transformation process, as well as the microstructure of the steel. The microstructure of the hot dip galvanizing TRIP steel consisted of ferrite, bainite, retained austenite and martensite during the short IBT time. The contents of ferrite, bainite, retained austenite and martensite with different IBT time were calculated. The results showed that when IBT time increased from 20 to 60 s, the volume of bainite increased from 14.31% to 16.95% and the volume of retained austenite increased from 13.64% to 16.28%; meanwhile, the volume of martensite decreased from 7.18% to 1.89%. Both the transformation induced plasticity of retained austenite and the hardening of martensite are effective, especially, the latter plays a dominant role in the steel containing 7.18% martensite which shows similar strength characteristics as dual-phase steel, but a better elongation. When martensite volume decreases to 1.89%, the steel shows typical mechanical properties of TRIP, as so small amount of martensite has no obvious effect on the mechanical properties.
关键词:
TRIP steel
,
isothermal bainitic transformation
,
martensite
,
mechanical property
SONG Ren-bo
,
XIANG Jian-ying
,
HOU Dong-po
钢铁研究学报(英文版)
A comparative study on mechanical properties and microstructure of 316L austenitic stainless steel between solution treated specimen and hot rolled specimen was conducted. After a specimen was subjected to solution treatment at 1050 ℃ for 6 min, its mechanical properties were determined through tensile and hardness tests. Based on the true stress vs true strain and engineering stress vs engineering strain flow curves, the work hardening rate has been explored. The results show that the solution treated specimen has an excellent combination of strength and elongation, and that this steel is easy to work-hardening during deformation. Optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffraction examinations were conducted, these reveal that twins in 316L austenitic stainless steel can be divided into suspended twin and transgranular twin which have different formation mechanisms in growth, and that the deformation induced martensite nucleated and grown in the shear band intersections can be observed, and that the fracture surfaces are mainly composed of dimples and exhibit a tough fracture character.
关键词:
316L
,
mechanical property
,
twin
,
martensite
,
fracture morphology
Fatih Hayat
,
Hüseyin Uzun
钢铁研究学报(英文版)
Grade A (GA) and high strength steel DH36 ship steels possessing different chemical compositions were used, and strength properties of GA steel and DH36 steel were compared. Additionally, 4 types of dual phase (DP) steels with different martensite volume fractions (MVFs) were produced from GA steel by means of heat treatment and they were compared with other steels through conducting microstructure, microhardness, tensile and impact tests. The fracture surfaces of specimens (DH36, GA and DP steels) exposed to tensile and Charpy impact tests were investigated by scanning electron microscope. Furthermore, it was found that the specimens quenched from 800 and 900 ℃ had better strength than DH36 steel. The tensile test results indicated that the tensile strength of DP steel water quenched from 900 ℃ was 3 times that of GA steel and twice that of DH36 steel.
关键词:
Grade A ship steel
,
DH36 ship steel
,
dual phase steel
,
martensite
,
mechanical property
,
fracture
