Precipitation hardening in Pb–0.08wt.%Ca–x%Sn alloys—the role of the pre-ageing

The precipitation hardening mechanism in both supersaturated and pre-aged Pb–0.08%Ca–x%Sn alloys was investigated by means of hardness and calorimetric measurements (differential scanning calorimetry, DSC) and transmission electron microscopy observations. DSC studies have shown that a pre-ageing tr...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2003-10, Vol.358 (1), p.233-242
Main Authors: Maı̂tre, Alexandre, Bourguignon, G, Fiorani, J.M, Ghanbaja, J, Steinmetz, J
Format: Article
Language:English
Subjects:
Applied sciences
Cross-disciplinary physics: materials science
rheology
DSC
Exact sciences and technology
Hardening
Lead alloys
Materials science
Metals. Metallurgy
Physics
Pre-ageing treatment
Solid solution hardening, precipitation hardening, and dispersion hardening
aging
Solid solution, precipitation, and dispersion hardening
aging
TEM
Treatment of materials and its effects on microstructure and properties
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Summary:The precipitation hardening mechanism in both supersaturated and pre-aged Pb–0.08%Ca–x%Sn alloys was investigated by means of hardness and calorimetric measurements (differential scanning calorimetry, DSC) and transmission electron microscopy observations. DSC studies have shown that a pre-ageing treatment of the ternary alloys at 363 K has a favourable effect by reducing the driving force of the overaging process. Furthermore, this preliminary treatment seems to give a finer and denser particle distribution than for only quenched alloys. This latter effect could explain the higher hardness of the pre-aged alloys. For the tin-rich alloy (≈2.0 wt.%), the pre-ageing treatment considerably reduces the micro-segregation of Sn at the grain (sub-)boundary. This phenomenon is accompanied by an increase of the precipitate tin content and also by the appearance of a lattice parameter mismatch of 2.9% between the L1 2 precipitate and the lead matrix. From all of these experimental results, it appears that the processes leading to the reduction in interfacial energy are not the rate determining step for the overageing.
ISSN:0921-5093
1873-4936
DOI:10.1016/S0921-5093(03)00283-1