The effects of the wavelength and orientation of machined grooves on a mold surface, casting speed, and melt superheat on the formation of surface marks on as-cast ingots were studied with an immersion casting tester ...The effects of the wavelength and orientation of machined grooves on a mold surface, casting speed, and melt superheat on the formation of surface marks on as-cast ingots were studied with an immersion casting tester and copper mold chill blocks. The mold surface topographies included a polished smooth surface, and those with machined unidirectional parallel contoured grooves oriented either parallel (vertical) or perpendicular (horizontal) to the casting direction. The unidirectional grooves were 0.232 mm deep with wavelength or spacing between 1 and 15 mm. The casting speed and melt superheat were between 1 and 200 mm/s, and 10 and 50 K, respectively. Two primary types of surface marks were observed on ingots cast with the copper mold with smooth surface topography, namely the finer and closely spaced ripples (Type I), and the widely spaced but coarser laps (Type II). The latter were more prevalent at the higher casting speeds and melt superheats. Qualitatively, formation of both types of surface marks on the as-cast ingots of the aluminum alloy 3003 appeared to be alleviated by increase in casting speed and melt superheat, and by the use of molds with grooved surface topography. In fact, casting with a mold surface with 1 mm spaced grooves that are perpendicular to the casting direction eliminated the formation of surface marks at casting speeds greater than 1 mm/s. It also improved the uniformity of the ingot subsurface microstructure and eliminated the associated subsurface segregation.展开更多
Reliable information on the solubility of hydrogen in aluminum and its alloys is critical to the effort of the aluminum industry to control and ameliorate the usually deleterious effects of hydrogen on the properties ...Reliable information on the solubility of hydrogen in aluminum and its alloys is critical to the effort of the aluminum industry to control and ameliorate the usually deleterious effects of hydrogen on the properties and performance of pure aluminum and aluminum alloy products. Unfortunately, there is a significant disparity between published values of hydrogen solubility in pure aluminum and aluminum alloys. This is because the measurement of the extremely low soluble hydrogen concentration in aluminum and its alloys is experimentally difficult. Also, the reproducibility, accuracy, and reliability of the hydrogen solubility values are very sensitive to the measurement techniques, test conditions, chemical composition, and state of the aluminum sample. Thus, no serious discussion of the reliability of reported values of hydrogen solubility in aluminum and its alloys can be undertaken without a critical assessment of the fundamental principles of the experimental techniques used in the determination of the reported values. In this article, a critical review of the fundamental principles of the experimental techniques used in the measurement of hydrogen solubility in liquid and solid pure aluminum and aluminum alloys is presented. In addition, the reliability and possible accuracy of reported values of hydrogen solubility in solid and liquid pure aluminum are critically assessed. Empirical equations for calculating hydrogen solubility in liquid and solid pure aluminum as a function of temperature and pressure, derived from the most reliable sets of data are recommended. At 101.3 kPa (1 atm.) hydrogen partial pressure, the most reliable values of hydrogen solubility at the melting point (833 K) of pure aluminum are 0.71 cm<sup>3</sup>/100g (i.e., 6.32 × 10<sup>-5</sup> wt.% H) and 0.043 cm<sup>3</sup>/100g (i.e., 3.81 × 10<sup>-6</sup> wt.% H), in the liquid and solid state, respectively. So, the partition coefficient of hydrogen in pure aluminum is 0.061.展开更多
文摘The effects of the wavelength and orientation of machined grooves on a mold surface, casting speed, and melt superheat on the formation of surface marks on as-cast ingots were studied with an immersion casting tester and copper mold chill blocks. The mold surface topographies included a polished smooth surface, and those with machined unidirectional parallel contoured grooves oriented either parallel (vertical) or perpendicular (horizontal) to the casting direction. The unidirectional grooves were 0.232 mm deep with wavelength or spacing between 1 and 15 mm. The casting speed and melt superheat were between 1 and 200 mm/s, and 10 and 50 K, respectively. Two primary types of surface marks were observed on ingots cast with the copper mold with smooth surface topography, namely the finer and closely spaced ripples (Type I), and the widely spaced but coarser laps (Type II). The latter were more prevalent at the higher casting speeds and melt superheats. Qualitatively, formation of both types of surface marks on the as-cast ingots of the aluminum alloy 3003 appeared to be alleviated by increase in casting speed and melt superheat, and by the use of molds with grooved surface topography. In fact, casting with a mold surface with 1 mm spaced grooves that are perpendicular to the casting direction eliminated the formation of surface marks at casting speeds greater than 1 mm/s. It also improved the uniformity of the ingot subsurface microstructure and eliminated the associated subsurface segregation.
文摘Reliable information on the solubility of hydrogen in aluminum and its alloys is critical to the effort of the aluminum industry to control and ameliorate the usually deleterious effects of hydrogen on the properties and performance of pure aluminum and aluminum alloy products. Unfortunately, there is a significant disparity between published values of hydrogen solubility in pure aluminum and aluminum alloys. This is because the measurement of the extremely low soluble hydrogen concentration in aluminum and its alloys is experimentally difficult. Also, the reproducibility, accuracy, and reliability of the hydrogen solubility values are very sensitive to the measurement techniques, test conditions, chemical composition, and state of the aluminum sample. Thus, no serious discussion of the reliability of reported values of hydrogen solubility in aluminum and its alloys can be undertaken without a critical assessment of the fundamental principles of the experimental techniques used in the determination of the reported values. In this article, a critical review of the fundamental principles of the experimental techniques used in the measurement of hydrogen solubility in liquid and solid pure aluminum and aluminum alloys is presented. In addition, the reliability and possible accuracy of reported values of hydrogen solubility in solid and liquid pure aluminum are critically assessed. Empirical equations for calculating hydrogen solubility in liquid and solid pure aluminum as a function of temperature and pressure, derived from the most reliable sets of data are recommended. At 101.3 kPa (1 atm.) hydrogen partial pressure, the most reliable values of hydrogen solubility at the melting point (833 K) of pure aluminum are 0.71 cm<sup>3</sup>/100g (i.e., 6.32 × 10<sup>-5</sup> wt.% H) and 0.043 cm<sup>3</sup>/100g (i.e., 3.81 × 10<sup>-6</sup> wt.% H), in the liquid and solid state, respectively. So, the partition coefficient of hydrogen in pure aluminum is 0.061.
