Abstract
Al-Mn-Fe-Si strips were fabricated via both the twin-roll casting(TRC)and the more conventional route,direct-chill casting(DC).The two types of strips prepared were subjected to thermal exposure at a series of temperatures.Uniaxial tensile tests after the thermal exposure showed that while the DC strip pre-sented a～74％decrease in the yield strength and～35％decrease in the ultimate tensile strength(UTS)after being exposed to 350℃for 12 h,the TRC strip,in contrast,maintained its strength at tempera-tures up to～460℃for the same duration.Systematic microstructure characterization revealed that the different thermal stability in the strength of the two types of strips arised from their distinct evolution in grain morphology and second phase particles during the thermal exposure.The calculation based on Cahn-Lucke-Stuwe(CLS)model suggested that due to the highly supersaturated solute atoms,at the be-ginning of the thermal exposure,the TRC strip experienced a strong solute drag which reduced the grain boundary migrating velocity to a value that is orders of magnitude smaller than that in the DC strip.With the progress of the thermal exposure,the solute atoms precipitated out,forming densely distributed sec-ond phase particles.For one thing,these particles stabilized the grain structure by inducing Zener pinning pressure which could be ten times higher than that in the DC strip,depending on the temperature.For another,they acted as dislocation obstacles and compensated for the strength loss owing to decreasing solution hardening.Both effects contributed to the TRC strip's fairly stable strength regarding thermal exposure below 460℃.The present work could guide the direct application of the TRC strips in the in-dustry.The results should also be helpful for the development of a fundamental framework for designing advanced TRC Al strips with improved mechanical properties at elevated temperatures.
基金项目
National Natural Science Foun-dation of China(51790482)
National Natural Science Foun-dation of China(51801147)
National Natural Science Foun-dation of China(51722104)
National Natural Science Foun-dation of China(51625103)
National Natural Science Foun-dation of China(51621063)
National Key Research and Development Pro-gram of China(2017YFB0702301)
NETL
NSTL
维普
万方数据