How Slight Solidification Rate Variations within Cast Plate Affect Mechanical Response: A Study on As‐Cast A356 Alloy with Cu Additions

Abstract

e present work investigates a narrow range of secondary dendrite arm spacing (SDAS), in an as-cast A356 alloy with and without copper (Cu) additions. Cu was added to the base A356 alloy melt to reach the target concentration of 0.5 and 1 wt.%. Samples were selected from 3 different positions within the cast plate, offering 30, 35, and 40 μm SDAS variants. Tensile curves revealed a strong influence between the specimen cutting position and strength, with a pronounced effect in the Cu-containing alloys. Hardness measurements did not confirm the tensile response; hence, to understand the phenomenon, microstructural features have been investigated in detail. Eutectic silicon (Si) particle equivalent diameter (ED) size decreased from the top (T) to the bottom (B) position of the cast. Eutectic Si particle surface area (A%) was found to be denser at the B as compared to the T and simultaneously in the Cu-containing alloy as compared to the Cu-free reference alloy. Backscattered electron (BSE) images were employed to investigate the nature of the Cu-rich intermetallic phases. In conclusion, electrical conductivity measurements were performed to confirm the trends observed.

The Influence of Copper Addition on Crack Initiation and Propagation in an Al-Si-Mg Alloy During Cyclic Testing

“…The percentage increase of YS was comparable to the results reported by Seifeddine et al [6] , who investigated alloys with chemical compositions, modification treatments, and solidification conditions similar to those described in the present work. Moreover, a drop in UTS occurs for samples with a Cu content of 3.2 wt%, whereas other authors reported this drop at lower Cu contents of around 1.5-2 wt% [3][4][5][6][7] . The increased quantity of Q and 𝜃 phases in Alloy Cu 3.0 was responsible for this significant drop in UTS and elongation, as highlighted by the analysis of fracture profiles and surfaces ( Fig.…”

“…As the investigated specimens were directionally solidified, the mechanical properties were beneficially influenced by Cu contents of greater than 1.5 wt%. Di Giovanni et al [7] observed an increase in the range of 25-30% for UTS with 1 wt% of Cu content, for SDAS going from 30 to 40 𝜇m.…”

“…Several studies of as-cast Al-Si-Mg alloys to which Cu was added investigated the influence of melt quality, porosity, and Cu intermetallic phases on tensile properties [4][5][6][7][8] . The results showed discrepancies due to the fact that the increases in yield strength (YS) and ultimate tensile strength (UTS) were not of similar magnitude for the same Cu contents.…”

The Influence of Foundry Scrap Returns on Chemical Composition and Microstructure Development of AlSi9Cu3 Alloy

“…This was due to the nature of the analysis, which also analysed the background of the sample. The phases were determined on the basis of EDS analyses and previous reports [17,18,[20][21][22][23].…”