The role of eutectic colonies in the tensile properties of a Sn-Zn eutectic solder alloy

Autor(es)

Ramos, Lidiane Silva ^[1] ; Reyes, Rodrigo Valenzuela ^[2] ; Gomes, Leonardo Fernandes ^[2] ; Garcia, Amauri ^[3] ; Spinelli, Jose Eduardo ^[4] ; Silva, Bismarck Luiz ^[1]

Afiliação do(s) autor(es)

^[1] Fed Univ Rio Grande do Norte UFRN, Dept Mat Engn, BR-59078970 Natal, RN - Brazil

^[2] Univ Fed Sao Carlos, Grad Program Mat Sci & Engn, BR-13565905 Sao Carlos, SP - Brazil

^[3] Univ Estadual Campinas, Dept Mfg & Mat Engn, UNICAMP, BR-13083860 Campinas, SP - Brazil

^[4] Fed Univ Sao Carlos UFSCar, Dept Mat Engn, BR-13565905 Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING; v. 776, MAR 3 2020.
• Citações Web of Science: 0

Resumo

The growth of eutectic colonies in Sn-Cu, Sn-Zn and Sn-Ag-Cu eutectic alloys has already been reported in the literature. However, relationships between this kind of microstructure and mechanical properties remain undetermined for solders. The use of water-cooled copper (Cu) and AISI 1020 low-C steel molds and the eutectic Sn9 wt.%Zn alloy make it possible to address this matter. The samples grown in the Cu mold demonstrated higher solidification rates than those developed in the low-C steel mold. Overall, the microstructure is constituted by Zn-lamellae embedded in a Sn-rich matrix. The Zn lamellae are not only uneven in thickness but also irregularly perforated. Due to Cu dissolution into the alloy, a small fraction of Cu5Zn8 intermetallic particles formed during solidification of the Sn-9 wt.%Zn alloy in the Cu mold. The contamination with Cu appears to be responsible for the improvement in the distribution of Zn-lamellae. The decrease in spacing between broken lamellae measured from SEM images, as well as a higher number of Zn particles per area, explain such occurrence. Ductility and tensile strength of different samples could allow the establishment of relationships among properties vs. eutectic colony spacing. For the Cu mold, the motion of Cu towards the alloy as well as higher solidification rates, allowed microstructures to be formed combining 6096 of strain to fracture and 52 MPa of ultimate tensile strength. These achievements are mainly due to the finest spacings of both the eutectic colony (lambda(c) = 36 mu m) and the Zn lamellae (lambda(L)=0.9 mu m), besides homogeneous distribution of Cu across the resulting microstructure. (AU)

• Processo FAPESP: 17/12741-6 - Aplicação de técnicas experimentais de solidificação, caracterização microestrutural e de propriedades na avaliação de ligas eutéticas e hipereutéticas à base de Al e Zn
• Beneficiário: José Eduardo Spinelli
• Modalidade de apoio: Auxílio à Pesquisa - Regular