Advanced Materials Research Vols. 146-147

Abstract: The welding cold cracking tendencies of Ca microalloyed HSLA steel was evaluated using crack sensitivity index Pcm, oblique Y-groove cracking test and the hardness of simulation CGHAZ(coarse grain heat affected zone) in this paper. The organizational structure and mechanical properties of simulation CGHAZ at different t8/5 was analysised in this paper two. The results show that:steel welding cold crack is less sensitive; the CaO pinning austenite grain boundaries effectively, fining the grain size of CGHAZ, increasing the amount of IFA, and improving the toughness of CGHAZ.The weldability of Ca microalloyed HSLA steel is good.

Abstract: The effect of post weld heat treatment on microstructures, tensile and corrosion properties of Inconel601 weld seam was investigated. The results indicated that the microstructure of weld metal consisted of coarser columnar grains with (Nb, Ti)-rich precipitations and laves phase distributed in them. Tensile and corrosion test displayed that the weld seam without any heat treatment exhibit the lowest mechanical and corrosion properties. Solution treatment at 1050°C was found to result in the considerable refinement of grain size and finally the improvement of mechanical and corrosion properties. It was also found that the specimens had the best mechanical and corrosion properties after heat treatment at 1150°C. However, with the treatment temperature increasing to 1200°C, the grain began to grow up, leading to the decrease of tensile strength and corrosion resistance.

Abstract: To understand the effects and mechanism of heat treatment to the high-pressure vessel performance, a series of different closed-shaped cavity heat treatment tests were conducted. Through tensile test, impact test, hardness test, OM and SEM test and so on, the heat treatment effects and micro mechanism of high-pressure vessel with different closed-shaped cavity were studied along the wall thickness direction. The results indicate that: with increase of volume of the closed-shaped cavity, the strength of container middle cross-section increases in the beginning and decreases afterward, the toughness falls first and then rises, and the plasticity changes little. The strength, plasticity and hardness increase gradually from inside to outside along the wall thickness direction. The hardness increases a little in the beginning, but then rises quickly when it comes close to the outer wall. After being quenched at 930°C and tempered at 580°C, the microstructure of the vessel material is mainly tempered sorbite. The structure grain boundary becomes more and more blur from inside to outside of the wall. Inner wall contains a small amount of residual austenite and tempered martensite. The fracture surface is toughness one.

Abstract: The geometrically frustrated material-deuteroxyl cobalt chlorides Co2(OD)3Cl sample was first, to the best of our knowledge, successfully synthesized in the same single phase as the famous Co2(OH)3Cl, and their mid-infrared absorption spectra (4000-400cm–1) and Raman spectra (4000-95 cm–1) are first, to the best of our knowledge, measured respectively by FTIR spectroscopy and Micro-Raman spectroscopy to study the corresponding relationship between their spectral properties and crystal structure. Through the comparative analysis of the four spectra we definitely assign or tentatively suggest the vibration modes of hydroxyl/deuteroxyl groups in the trimeric hydrogen bond environment, (OH/D)–Co–(OH/D), and (H/D3···Cl)–Co–(Cl···H/D3). These results can be propitious to the low temperature spectral properties of Co2(OH)3Cl and Co2(OD)3Cl which must help to understand the underlying physics of their exotic geometric frustration phenomenon.

Abstract: The principal purpose of this paper are to determine the viscosity of refining slag with the features of high crystallinity and strongly oxidizability, and to solve the problem that slag sticked onto the RH immersion tube during the RH refining process. Then, the fluid length method was used to determine the viscosity, and the effect of compositions on melting point and viscosity of refining ladle slag was studied. Overall, the relationship between viscosity and fluid length was acquired, and it achieved the slag with lower melting point and good fluidity which can avoid slag building-up on RH immersion tube by adjusting the basicity of refining slag to 4-5, the content of Al2O3 to 14-15% with additives.

Abstract: Basic copper chloride Cu2(OH)3Cl and Cu2(OD)3Cl polycrystalline sample were successfully synthesized in the same single phase of clinoatacamite-structure, and the latter’s mid-infrared absorption spectra (4000-400cm–1) and Raman spectra (4000-95cm–1) were first, to the best of our knowledge, measured respectively by FTIR spectroscopy and Micro-Raman spectroscopy to study the corresponding relationship between their spectral properties and crystal structure. Through the comparative analysis of the four spectra we definitely assign or tentatively suggest the vibration modes of OH/D groups in the trimeric hydrogen bond environment, (H/DO)–Cu–(OH/D), Cl–Cu–Cl. These results can be propitious to their low temperature spectral properties which must help to understand the underlying physics of their exotic geometric frustration phenomenon.

Abstract: From more than one uniaxial tension test curve, it can be found that mechanics property of sheet metal is inhomogeneous. Based on this truth, a new method for prediction of forming limit of sheet metal is proposed. Using this method, theoretical FLDs are obtained under proportional loading path based on Hill48 yield criterion. The effects of several material parameters on forming limit are obtained. Similarities and differences between this method and M-K instability theory are analyzed and some advices on the application of this method are given.

Abstract: Continuous casting has been widely applied in the production of steels and other metals. However, it has been rarely used in producing high speed steels, which are still manufactured by the conventional method of mould-casting. Thus, little is known about the microstructure of high speed steels made by the continuous casting technology. In the present work, AISI M2 steel is produced by horizontal continuous casting and the difference of solidification microstructure of ingots by different casting technologies has been examined. The results show that the networks of M2C eutectic carbides are greatly refined in the ingot by continuous casting compared to that by mould casting. Meanwhile, the morphology of M2C eutectic carbides changes from the plate-like type to the fibrous one, due to the increasing cooling rates. Compared with the plate-like M2C, the fibrous M2C in continuous casting ingots is less stable and decomposes faster at high temperatures, spheroidizing obviously after heating and refining dimensions of carbides.

Abstract: The different dilatometric curves of continuous cooling transformation with the different cooling rates were determined by means of Gleeble-2000 thermal simulation machine. The CCT curve of BVRE heavy rail steel was obtained by measuring the dilatometric curves and metallographic analysis. And the effects and mechanisms of vanadium on the phase transformation and microstructure of BVRE heavy rail steel were investigated. It is found that, the BVRE heavy rail steel only takes place pearlite and martensite transformation during continuous cooling. The CCT curve of BVRE heavy rail steel is moved to lower right with increasing vanadium content, which indicates that vanadium can obviously improve the stability of super cooled austenite and delay the pearlite transformation. When the content of vanadium is increased from 0.052% to 0.12%, the shortest incubation time of pearlite transformation is increased from 30s to 59s. When the cooling rate ≤ 5 ·s-1, with increasing vanadium content, both starting and finishing temperatures of pearlite transformation are decreased at different extent, meanwhile the pearlite is refined and the pearlite percentage is notably decreased. When the cooling rate is 2 ·s-1, the pearlite percentage is decreased from 65.7% to 35.9% with increasing vanadium content. When the content of vanadium is increased from 0.052% to 0.12%, the critical cooling rate of quenching is decreased from 13 ·s-1 to 7 ·s-1, thus the hardenability of BVRE heavy rail steel is improved.

Abstract: The Mg matrix composite (Mg2Si/Mg-5Zn-2.5Er) was prepared using repeated plastic working (RPW) technique. and the effects of the number of RPW cycles on the microstructure and mechanical properties of these composites were investigated. The results indicated that the added silicon particles fully reacted with the magnesium matrix, and theMg2Si/Mg-5Zn-2.5Er composites were successfully achieved. When the number of RPW cycle increased, the size of the Mg2Si particles decreased, and the grain size of the matrix alloy reached the minimum when 200 RPW cycles was used. The best mechanical properties were also identified as 394 MPa ultimate strength, and 363 MPa yield strength, when 200 RPW cycles were used.