The Reaction Products of the Al–Nb–B2O3–CuO System in an Al 6063 Alloy Melt and Their Influence on the Alloy’s Structure and Characteristics

To meet aero-engine aluminum skirt requirements, an experiment was carried out using Al–Nb–B₂O₃–CuO as the reaction system and a 6063 aluminum alloy melt as the reaction medium for a contact reaction, and 6063 aluminum matrix composites containing in situ particles were prepared with the near-liquid-phase line-casting method after the reaction was completed. The effects of the reactant molar ratio and the preheating temperature on the in situ reaction process and products were explored in order to determine the influence of in situ-reaction-product features on the organization and the qualities of the composites. Thermodynamic calculations, DSC analysis, and experiments revealed that the reaction could continue when the molar ratio of the reactants of Al–Nb–B₂O₃–CuO was 6:1:1:1.5. A kinetic study revealed that the Al thermal reaction in the system produced Al₂O₃ and [B], and the [B] atoms interacted with Nb to generate NbB₂. With increasing temperature, the interaction between the Nb and the AlB₂ produced hexagonal NbB₂ particles with an average longitudinal size of 1 μm and subspherical Al₂O₃ particles with an average longitudinal size of 0.2 μm. The microstructure of the composites was reasonably fine, with an estimated equiaxed crystal size of around 22 μm, a tensile strength of 170 MPa, a yield strength of 135 MPa, an elongation of 13.4%, and a fracture energy of 17.05 × 10⁵ KJ/m³, with a content of 2.3 wt% complex-phase particles. When compared to the matrix alloy without addition, the NbB₂ and Al₂O₃ particles produced by the in situ reaction had a significant refinement effect on the microstructure of the alloy, and the plasticity of the composite in the as-cast state was improved while maintaining higher strength and better overall mechanical properties, allowing for industrial mass production.     

Association of glycated hemoglobin at an early stage of pregnancy with the risk of gestational diabetes mellitus among non‐diabetic women in Japan: The Japan Environment and Children’s Study

Aims/IntroductionGestational diabetes mellitus (GDM) is one of the most common complications of pregnancy and is associated with adverse pregnancy outcomes. This study aimed to explore the associations between glycated hemoglobin (HbA1c) levels at the early stage of pregnancy and the GDM risk among non‐diabetic women in a nationwide study in Japan. In addition, the relationship between GDM and adverse pregnancy outcomes was also analyzed.Materials and MethodsThis cohort study (n = 89,799) used data from the Japan Environment and Children’s Study. We stratified the participants into four groups according to HbA1c levels at an early stage of pregnancy. We investigated the association of HbA1c at an early stage of pregnancy with the risk of GDM, and of GDM with the risk of some representative adverse pregnancy outcomes, using the multiple logistic regression model with adjustment for potential confounders.ResultsThe adjusted odds ratio for GDM per 0.1 percentage point increase in HbA1c (%) was 1.20. The adjusted odds ratio for developing GDM was significantly increased in women from the HbA1c 5.0–5.4% category. GDM significantly increased the adjusted odds ratio for adverse pregnancy outcomes, such as hypertensive disorders of pregnancy, polyhydramnios and premature birth.ConclusionsHigh‐normal HbA1c levels at the early stage of pregnancy are significantly associated with GDM risk in women in Japan. GDM was significantly associated with adverse pregnancy outcomes.