Recrystallization during the Discontinuous Precipitation of β-Sn in 95Pb-5Sn and 85Pb-15Sn Solder Alloys

• Published in: Scripta materialia 1998-05, Vol.38 (11), p.1677-1684
• Main Authors: Kim, Jeong Seog, Kang, Min-Sik, Lee, Sung Bo
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Solid-phase precipitation
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/S1359-6462(98)00093-1

The 85Pb-15Sn and 95Pb-5Sn alloys show discontinuous precipitation behavior. The microstructure of 95Pb-5Sn alloy showing the DP cells growing concurrently with the migration of the original grain boundaries implies that the conventional cell growth mechanism operates in the Pb-Sn alloy. However, the variation of cell size with the alloy composition and the aging temperature was so extensive that the conventional mechanism is not sufficient to explain all the range of the cell size variation. The extraordinarily small cell size can be attributed only to the recrystallization during discontinuous precipitation. The recrystallization during DP reaction is similar to the CIR. A large degree of supersaturation in the solid solution results in a large misfit strain and provides a favorable condition for the recrystallization. In Pb-Sn alloys, DP cells become smaller with higher Sn-content and lower aging temperature consistently with the misfit strain model. The misfit strain for inducing the recrystallization during the DP is considered to be approx5x10 exp -3 judging from the calculated misfit strains of several materials showing the recrystallization and CIIM > The importance of this study is the observation of grain refinement by the DP and the proposition of a recrystallization mechanism during the discontinuous precipitation reaction.