Advanced Materials Research Vols. 915-916

Abstract: Uniaxial creep tests on micro-regions of P92 steel base metal and welding HAZ specimens were carried out at 923 K and under different stress levels. The creep equation of index of B and n was obtained from the test data fitted by using least square method. Then, creep crack growth tests based on the reference stress method on P92 steel base metal and welding HAZ compact tensile samples were carried out at 923 K and under stress intensity factor K of 18 MPa·m^1/2. From the calculated and experimental data, it was found that a good relationship existed between the creep crack growth rate da/dc and high temperature creep fracture parameter C*. The reference stress method was verified to calculate the C* of compact tension specimens and can predict the creep crack growth rate of the P92 steel base metal and welding HAZ materials under steady state creep conditions. At the same time, high temperature defect evaluation parameters of D₀ and Φ were obtained by fitting the linear parts in the relation curves using the log-log method. This study provides tests data on the defects evaluation and life prediction of P92 steel welding materials.

Abstract: The character of microstructure in the segregation of 82B wire with two different stelmor control cooling procedures and kinetics of eutectoid transformation of segregation through thermal simulation in the range of 400-600°C were researched. The longitudinal section segregation microstructure and composition were analyzed by OMSEMWDS. The thermal simulation results show that the length of martensite segregation bands is decreased holding 10-40s above 500°C, and martensite band in the core of wire where the content of Mn and Cr elements is higher than matrix because of segregation. Furthermore, Stelmor control cooling experiments in the high speed wire mill confirms that there is a critical temperature500°C to 82B wire above which the eutectoid transformation in the segregation is possible, and enough time above the critical temperature in the Stelmor control cooling lids is the key to optimizing procedure.

Abstract: Stainless steel products are used in some building for excellent performance. But actually using in complex environment and influencing by several factors, the products may be eroded. The objective of this study was to account for the cause of the corrosion of the submitted funnel sample. In general, the approach is to formulate and conduct a series of laboratory tests, and interpret the results. Based on the findings, corrosion of the submitted stainless steel funnel could be attributed to three factors, such as material factor, site condition and corrosion.

Abstract: The pure copper tube with strong axial orientation columnar grain and equiaxed grain respectively were rolled using a three-roller precision tube mill. Optical microscope, hardness testing machine and universal testing machine were used to investigate the microstructure and mechanical properties of the pure copper tube rolled with different deformation degrees. The results show that the pure copper tube with two kinds of microstructure can be directly rolled from the dimension of Φ68.5mm×57.9mm to Φ34.7×30.4mm by 8 passes with accumulated deformation degree nearly 80% and without intermediate annealing. With the increasing deformation degree, the primary columnar grain boundaries of the pure copper tube with columnar grain blurred gradually until completely disappeared. However, the microstructures of pure copper tube with equiaxed grain completely transformed into fibrous microstructures when the deformation degree reaches to 79.11%. The columnar grain is without transverse grain boundaries but with small-angle boundary, which is conducive to axial deformation. It is also found that with the increasing deformation degree, the tensile strength of pure copper tube increased steadily, while the elongation decreased gradually. The elongation of pure copper tube with columnar grains is higher and the microhardness is lower than that of equiaxed grains, indicating that the cold deformation properties of pure copper tube with columnar grain was more excellent.

Abstract: The dynamic mechanical property and microstructure evolution in localized shear deformation was investigated in the Al-5.6%Mg-0.75%M-0.25%Er alloy cold rolled to 80% reduction by using Gleeble 3500 compression at the strain rate of 0.01~500s^-1. The results show that both a critical strain rate and strain were required for the formation of local shear band under high strain rate compression. The initial Lamellar Boundaries (LBs) in the matrix region are parallel to the rolling direction (RD), with average boundary spacing of 0.25μm; The LBs within the shear bands region have a angle of 20° with RD, whose boundary spacing is ranging from 0.1 to 0.2μm. The LBs gradually rotate to an angle of 20° with RD and finally become wavy shape during the dynamic deformation.

Abstract: The level of ferrite/pearlite banding in gear steel can be affected significantly by cooling rates, however, different sizes own diverse bands in the same cooling rate. The lower-level degree banding was got under the faster cooling speed, whereas the higher-level degree banding under the slower cooling speed. The alloying elements segregation can be characterized in the fixed speed according to the banding. Banded segregation in a hot rolled SAE8620 gear steel was investigated by DIL805A dilatometer, OM, electron microprobe analysis(EPMA). The transformation temperature of rich solute and poor solute were calculated by JMatPro software. Meanwhile, the diffusion distance of carbon was also figured by DICTRA. Results showed that the difference of Ar3 temperatures for solute-depleted and solute-rich zones will impact the banded intensity, while the diffusion distance of carbon decrease with an increasingly of cooling rate, the banded structure relieved. The corresponding band adopted 0.2 °C/s cooling rate can characterize the first banded segregation of alloy elements.

Abstract: The effect of the alloying elements Cu and Mg, the solution and artificial aging process on the microstructure and property were investigated. Solution treatment was carried out at 535 ± 5°C in different time for the Al-Si-Cu-Mg casting alloy, and the artificial aging was carried out at 160 ± 5°C and 175 ± 5°C and190 ± 5°C in different time. The microstructure has been investigated by Optical Microscopy, Scanning Electron Microscopy (SEM). We found that most of Cu and Mg element in the alloy gathered and formed multivariate composite phase at grain boundaries. With the increasing of solid solution time, the intermetallic phases will be dissolution into the matrix, and if the solid solution time is long enough, they will be distributed uniformly in alloy. With the increase of the aging temperature, the time for aging peak will be shorter, but the peak will be lower. Finally, we determine the optimum heat treatment process is 535°C × 12h + 175°C × 8h。

Abstract: A Cu-24 wt % Ag composite alloy is prepared to reveal the evolutions of microstructures, mechanical properties and textures formed by cold rolling. A typical alternating distribution of Cu and Ag phase layers is observed, which becomes much finer with increasing cold rolling reduction. Copper texture ((112)<11-1> texture) and Goss texture ((110)<001> texture) with high intensities are found in the Cu phase of cold rolled samples. Ag phase containing strong Goss texture and weak Brass texture are observed, quite different from the case in cold rolled pure Ag. Significant change of textures, from the Goss texture to (111) textures with increasing rolling reduction, has been found of Ag phase. The strengthening mechanism of this Cu-Ag composite is described by a equation similar to the HallPetch relationship, the fitted results based on which shows good agreement with the experimental data when the layer thickness is lower than 100-200 nm.

Abstract: The optimal control of carbon content is one of the most important factors of excellent properties of tungsten steel material. The control of carbon content in tungsten steel materials could be started from several ways. This paper discusses the control of carbon content of tungsten steel material in sintering process. In this paper, that is the main measure to control the carbon content in the sintering process: The control of balance between hydrogen and carbon in pre sintering process; The control of balance between carbon and oxygen in vacuum sintering.

Abstract: The 2D axisymmetric smoothed particle hydrodynamics (ASPH) has been adopted to study the perforation of AA5083-H116 aluminum plates with ogive-nose hard steel projectiles. The deceleration history curves of the projectile by the ASPH were presented for three impact conditions. Impact vs. residual velocity curves were constructed and the ballistic limit velocity was determined. The computational residual velocities and the ballistic limit velocities from the ASPH agree well with available experimental data. The study shows that the ASPH is able to emulate the perforation of aluminum plates as observed in the experimental investigations of high velocity impact.