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Phase transformation behavior in a multipurpose dental casting gold alloy during continuous heating
H I Kim1, H J Seol, K Hisatsune
1Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739, Korea.
Journal of Materials Science. Materials in Medicine
|September 7, 2004
Summary
This study investigates phase transformation in dental gold alloys during heating. Discontinuous precipitation causes hardening, while growth leads to softening, due to a novel PtZn phase.
Area of Science:
- Materials Science
- Metallurgy
- Dental Materials Science
Background:
- Dental casting gold alloys are crucial in prosthodontics.
- Understanding their phase transformation behavior during heating is essential for optimizing mechanical properties and clinical performance.
- Previous studies often focused on traditional alloy compositions, necessitating research into newer formulations.
Purpose of the Study:
- To investigate the phase transformation mechanisms in a multipurpose dental casting gold alloy subjected to continuous heating.
- To correlate observed microstructural changes with alterations in electrical resistivity and hardness.
- To elucidate the role of the PtZn ordered phase in the alloy's behavior.
Main Methods:
- Electrical resistivity measurements
- Hardness testing
- X-ray diffraction (XRD)
- Scanning electron microscopy (SEM)
- Transmission electron microscopy (TEM)
Main Results:
- Phase transformation behavior was characterized by specific reaction sequences involving alpha1 (face-centred cubic) and alpha2 (L1(2)) phases, leading to the formation of a beta (L1(0)) phase.
- Discontinuous precipitation of very fine nodules was identified as the primary mechanism responsible for alloy hardening.
- Subsequent growth of these precipitates resulted in a softening effect, indicating a complex interplay between different microstructural evolution stages.
Conclusions:
- The studied multipurpose gold alloy exhibits unique phase transformation characteristics driven by the presence of a PtZn ordered phase with L1(0) structure.
- The observed hardening and softening phenomena are directly linked to the discontinuous precipitation and subsequent growth of microstructural phases.
- These findings provide critical insights for the development and application of advanced gold alloys in dentistry.