Evolution of Annealing Twins in a Hot Deformed Nickel-Based Superalloy.

The hot deformation characteristics of a GH4169 superalloy are investigated at the temperature and strain rate ranges of 1193-1313 K and 0.01-1 s-1, respectively, through Gleeble-3500 simulator. The hot deformed microstructures are analyzed by optical microscopy (OM), transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD) technology. The effects of deformation parameters on the features of flow curves and annealing twins are discussed in detail. It is found that the shapes of flow curves are greatly affected by the deformation temperature. Broad peaks appear at low deformation temperatures or high strain rates. In addition, the evolution of annealing twins is significantly sensitive to the deformation degree, temperature, and strain rate. The fraction of annealing twins first decreases and then rises with the added deformation degree. This is because the initial annealing twin characters disappear at the relatively small strains, while the annealing twins rapidly generate with the growth of dynamic recrystallized grains during the subsequent hot deformation. The fraction of annealing twins is relatively high when the deformation temperature is high or the strain rate is low. In addition, the important role of annealing twins on dynamic recrystallization (DRX) behaviors are elucidated. The obvious bulging at initial twin boundaries, and the coherency of annealing twin boundaries with dynamic recrystallized grain boundaries, indicates that annealing twins can motivate the DRX nucleation during the hot deformation.

[Manipulative reduction and lateral percutaneous K-wire fixation for treatment of supracondylar humerus fractures in 128 children].

OBJECTIVE: To explore the clinical effect of manipulative reduction and lateral percutaneous K-wire fixation on supracondylar humerus fractures. METHODS: From Feb. 2004 to Jun. 2010,128 cases of supracondylar humeros fractures in children (96 boys and 32 girls) were treated by manipulative reduction and lateral percutaneous K-wire fixation. The average age of the children was 8 years old ranging from 2 to 15 years. Among them, 112 cases were extension fractures, 16 were flexion type; 102 cases belonged to ulnar deviation, and 26 cases belonged to radial deviation. After treatment, the elbow flexion range and carrying angle of the children were measured under the Flynn evaluation standard while considering the postoperative complications status to analyze the clinical effect on manipulative reduction and lateral percutaneous K-wire fixation. RESULTS: All these children were followed up from 2 to 36 months (16 months on average). According to Flynn evaluation standard,the result were excellent in 116 children (90.6% of the total patients), good in 11 (8.6%), fair in 1 (0.8%). No infection, no ischemic muscular atrophy and no nerve damage had been found during the treatment. CONCLUSION: The manipulative reduction and lateral percutaneous K-wire fixation of supracondylar humerus fractures in children has small wound, is stable and reliable, easy to be operated, safe and effective and low cost. What's more, it can also avoid the complication caused by conservative treatment and operation. It is a good treatment of supracondylar humerus fractures in children.