Yiyu Wang

Iron nutrition in childhood malignancy

Status of iron nutrition along with demographic, anthropometric, dietary, and biochemical parameters were recorded in 98 pediatric cancer patients at the time of referral. Dietary intake in each patient was analyzed for calories, protein, and iron. Blood specimens were analyzed for hemoglobin (Hgb), hematocrit (Hct), iron, total iron-binding capacity (TIBC), transferrin, and ferritin. Dietary intake measures were assessed according to each subjects Recommended Dietary Allowance (RDA). The results were compared among three diagnostic groups, namely, benign, solid tumor, and hematopoietic. The nutrient lowest in intake was iron. The overall measures revealed significant differences between the benign and hematopoietic groups in all parameters except TIBC and transferrin. A correlation coefficient of 0.55 (p less than 10(-5) between transferrin and TIBC was generated in our patients. Significant differences were noted for ferritin in the acute lymphocytic leukemia (p = 0.0001) and lymphoma (p = 0.0007) groups when compared with the benign group. A correlation coefficient of 0.55 (p less than 10(-5) was generated in our patients. A 3-month follow-up assessment was conducted in order to document the effects of therapy. Tumor response and progression was compared to changes in ferritin levels from baseline to follow-up. Our results support the literature, that ferritin is a sensitive tumor marker in various malignancies.

Identification of Inverse Bainite in Fe-0.84C-1Cr-1Mn Hypereutectoid Low Alloy Steel

A unique dilatation trend is observed for isothermal bainite transformation in Fe-0.84 pct C-1 pct Cr-1 pct Mn steel. The dilatation is found to occur in two stages with volumetric contraction dominating the first stage, followed by volumetric expansion dominating the second stage. Through electron microscopic characterization, bainitic microstructure is identified as inverse bainite with cementite (Fe3C) nucleating first from supersaturated austenite followed by the transformation of ferrite and secondary carbides (Fe3C, Fe2C, and Fe5C2) from carbon-depleted austenite.

Correlation Between Intercritical Heat-Affected Zone and Type IV Creep Damage Zone in Grade 91 Steel

A soft zone in Cr-Mo steel weldments has been reported to accompany the infamous Type IV cracking, the highly localized creep damage in the heat-affected zone of creep-resistant steels. However, the microstructural features and formation mechanism of this soft zone are not well understood. In this study, using microhardness profiling and microstructural verification, the initial soft zone in the as-welded condition was identified to be located in the intercritical heat-affected zone of P91 steel weldments. It has a mixed structure, consisting of Cr-rich re-austenitized prior austenite grains and fine Cr-depleted, tempered martensite grains retained from the base metal. The presence of these further-tempered retained grains, originating from the base metal, is directly responsible for the hardness reduction of the identified soft zone in the as-welded condition. The identified soft zone exhibits a high location consistency at three thermal stages. Local chemistry analysis and thermodynamic calculation show that the lower chromium concentrations inside these retained grains thermodynamically decrease their potentials for austenitic transformation during welding. Heterogeneous grain growth is observed in the soft zone during postweld heat treatment. The mismatch of strengths between the weak Cr-depleted grains and strong Cr-rich grains enhances the creep damage. Local deformation of the weaker Cr-depleted grains accelerates the formation of creep cavities.

A dilatometric analysis of inverse bainite transformation

The unique two-stage dilatation curve observed during the inverse bainite transformation of a hypereutectoid low alloy steel is analyzed to understand the transformation kinetics. A new algorithm is proposed to extract the bainitic phase fractions from the raw dilatometry data. The proposed data extraction algorithm is generic that relies only on the density of phases involved in the transformation. To verify the extracted phase fraction, a kinetics model is developed using the principles of diffusion and Johnson–Mehl–Avrami–Kolmogorov kinetics. The predicted phase fractions by the kinetics model agree fairly well with the experimental phase fraction results from dilatometry, metallography, and XRD. The two-stage transformation can be explained by the kinetics of inverse bainite as a diffusion-controlled transformation product. The transformation proceeds in a para-equilibrium mode, involving only the diffusion of carbon at the inverse bainite/parent austenite interface

Microstructural analysis of fracture in heat-affected zone of two ×70 pipeline steel weldments

ABSTRACT In the previous study, different crack propagation behaviours (ductile fracture and brittle cleavage fracture) were observed in two ×70 pipeline steel weldments (13.4 and 17.8-mm-thick) during single-edge notched bend testing. To further understand these two fracture behaviours, detailed microstructures of the base metal (BM), fine-grained heat-affected zone (FGHAZ), and coarse-grained heat-affected zone (CGHAZ) of these two ×70 pipeline steel weldments have been analysed. The results show that the initial structure of the two pipe BMs and different welding cooling rates owing to different thicknesses contributed to structural variations of the correlated sub-regions of the HAZ. For both weldments, the FGHAZ close to the BM has the highest fraction of the high-angle grain boundaries, the finest grain size, the lowest local strain levels, and the highest fraction of recrystallised ferrite grains. The CGHAZ of the 17.8-mm-thick pipe welds exhibits the lowest toughness with the highest hardness, a high frequency of deformed grains, the highest local strain level, and the highest density of preferred {100} cleavage planes than the other sub-regions in the HAZ. The high density of the {100}<011> texture components in the HAZ may cause the cleavage micro-cracks to propagate toward the BM at an approximate 45° angle to the original crack plane during bending tests.

Homogenisation of austenite during non-equilibrium heating in hypereutectoid steels

ABSTRACT The homogenisation (Stage III) of austenite during non-equilibrium heating of hypereutectoid steels has been characterised for the first time through dilatometric strain measurements and electron microscopic techniques. It has been found that the homogenisation temperature (Ach) is significantly higher than the cementite dissolution temperature (Acm). Though there is a complete conversion of low-temperature constituents to austenite above the Acm, a significant segregation of carbon in the austenite is observed below the Ach. Performing heat treatment with an incomplete austenitisation between the Acm and the Ach temperature can affect the subsequent on-cooling phase transformations. It is proposed that the Ach temperature should be used as the full austenitisation temperature in hypereutectoid steels.