Impact strength and structural refinement of A380 aluminum alloy produced through gas-induced semi-solid process and Sr addition

Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid (GISS) process. The effects of argon inert gas flow rate, starting temperature and duration of gas purging as key GISS parameters and also modification with Sr on the structural refinements, hardness and impact strength of GISS alloys were investigated. Microstructural evolution shows that there is an important effect of the pouring temperature and Sr addition on the morphology and size of primary alpha(A1) in the alloy to change from coarse dendritic to fine globular structure. The best sample which has fine grains of 51.18 mu m in average size and a high level of globularity of 0.89 is achieved from a GISS processing of Sr modified alloy in which the gas purging started at 610 degrees C. The impact strength of the GISS optimized samples ((4.67 +/- 0.18) J/cm(2)) shows an increase of about 40% with respect to the as-cast sample due to the globular structure and fibrous Si morphology. Moreover, the hardness of the optimized GISS sample ((89.34 +/- 2.85) HB) increases to (93.84 +/- 3.14) HB by modification with the Sr and GISS process. The fracture surface of Sr modified alloy is also dominated by complex topography showing typical ductile fracture features.

Automated summary

In this study, gas induced semi-solid (GISS) process was used for semi-solid processing of A380 aluminum alloy. The effects of argon inert gas flow rate, starting temperature, and duration of gas purging as key GISS parameters, as well as modification with Sr, on the structural refinements, hardness, and impact strength of GISS alloys were investigated. The results showed that the morphology and size of primary alpha(A1) in the alloy can be changed from coarse dendritic to fine globular structure by adjusting the pouring temperature and adding Sr. The optimized GISS sample obtained from Sr modified alloy with gas purging starting at 610 degrees C exhibited fine grains and a high level of globularity, resulting in significantly increased impact strength and hardness.