Negative strain rate sensitivity of yield strength of Al-Si alloy additive-manufactured using laser powder bed fusion. (May 2022)

• Record Type: Journal Article
• Authors: Takata, Naoki; Liu, Mulin; Suzuki, Asuka; Kobashi, Makoto; Kato, Masaki
• Is Part Of: Scripta materialia. Number 213(2022)
• Publication Date: 2022-05
• Subjects: Laser powder bed fusion -- Selective laser melting -- Aluminum alloy -- Strain-rate sensitivity -- Dynamic precipitation; Materials -- Periodicals; Metallurgy -- Periodicals; Metalen; Legeringen; Materiaalkunde; Metals, metalworking and machinery industries; Metals; Electronic journals; 620.11
• DOI: 10.1016/j.scriptamat.2022.114635
• Languages: English
• ISSNs: 1359-6462

Abstract

Abstract: This article reports an unexpected finding of the mechanical behavior of Al-12%Si alloy manufactured using the laser powder bed fusion (L-PBF) process. The as-manufactured specimen has a negative strain rate sensitivity of flow stress at an early stage of tensile deformation (below 3% in strain). The post heat-treated specimens exhibited a positive strain-rate sensitivity and none of these specimens exhibited a serrated stress-strain curve, indicating a mechanism different from the Portevin–LeChatelier effect. Transmission electron microscopy revealed the dynamic precipitation of the nano-sized Si-phase inside the supersaturated solid solution of the α-Al matrix in the as-manufactured specimen deformed at ambient temperatures. The dynamically precipitated Si phase interacted with the introduced dislocations, enhancing the flow stress during the early stages of plastic deformation. The dynamic precipitation could contribute to the negative strain-rate sensitivity of the flow stress at an early stage of tensile deformation (including the yield strength). Graphical abstract: Image, graphical abstract