PUKYONG

Quantitative evaluation of hot tearing susceptibility in Al-Si-Cu casting alloy with different Co content

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Abstract
Al-Si-Cu alloys benefit from the addition of copper for better hardness and strength through precipitation hardening, which results in remarkably strong alloys. However, the addition of copper expands the solidification range of Al-Si-Cu alloys, and due to this, these alloys become more prone to hot tearing, which is one of the most common and serious fracture phenomena encountered during solidification. The conventional evaluation method of the hot tearing properties of an alloy is a relative and qualitative analysis approach that does not provide quantitative data about this phenomenon. In the present study, the mold itself part of a device developed in Instone et al. was partially modified to obtain more reliable quantitative data pertaining to the hot tearing properties of an Al-Si-Cu casting alloy. To assess the influence of the Cu element, four levels of Cu contents were tested (0.5, 1.0, 3.0, and 5.0wt.%) in the Al-Si-Cu system alloy, and the hot tearing properties were evaluated in each case. As the Cu content was increased, the hot tearing strength decreased to 2.26, 1.53, 1.18, and 1.04 MPa, respectively. At the moment hot tearing occurred, the corresponding solid fraction and solidification rate decreased at the same temperature due to the increase in the solid-liquid coexistence range as the Cu content increased. The morphology of the fracture surfaces was changed from dendrites to dendrites covered with residual liquid, and CuAl2 phases were observed in the vicinity of hot tearing.
Author(s)
MUNKHDELGER CHINBAT
Issued Date
2022
Awarded Date
2022. 2
Type
Dissertation
Keyword
hot tearing tendency Quantitative evaluation of hot tearing Al-Si-Cu casting alloy effect of copper
Publisher
부경대학교
URI
https://repository.pknu.ac.kr:8443/handle/2021.oak/24162
http://pknu.dcollection.net/common/orgView/200000606976
Affiliation
Pukyong National University, Graduate school of industry
Department
산업대학원 금속공학과
Advisor
KoMinSeong
Table Of Contents
1. Introduction 1
2. Literature review 4
2.1 Al-Si-Cu casting alloy 4
2.2 Hot tearing phenomenon and theories 6
2.2.1 Qualitative evaluation 12
2.2.2 Quantitative evaluation 13
2.3 Effect of Cu on solid fraction 14
2.4 Summary of literature review 20
3. Experimental procedure 26
3.1 Specimen preparation 26
3.2 Microstructure observation and Thermal analysis 28
3.3 Evaluation of hot tearing strength through mold modified device 28
4. Results and discussion 32
4.1 Microstructure observation 32
4.2 Evaluation of hot tearing strength 41
4.2.1 Thermodynamic analysis on the test alloys through a simulation S/W 41
4.2.2 Effect of Cu content on hot tearing strength 43
4.2.3 Effect of residual liquid on hot tearing strength 44
5. Conclusion 57
Degree
Master
Appears in Collections:
산업대학원 > 금속공학과
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