초음파 용탕 처리 및 냉각속도가 Al-18Si-4Cu-3Ni 피스톤용 합금의 미세조직과 고온인장특성에 미치는 영향

• Published in: 대한금속·재료학회지, 55(6) Vol. 55; no. 6; pp. 396 - 404
• Main Authors: 윤재희, Jea-hee Yoon, 조영희, Young-hee Cho, 정재길, Jae-gil Jung, 이정무, Jung-moo Lee, 박익민, Ik Min Park
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 05.06.2017; 대한금속·재료학회
• Subjects: elevated temperature tensile properties; hypereutectic Al-18Si casting alloy; interconnectivity; microstructure; ultrasonic melt treatment; 재료공학
• ISSN: 1738-8228; 2288-8241
• DOI: 10.3365/KJMM.2017.55.6.396

The influence of ultrasonic melt treatment (UST) combined with a change in cooling rates on the microstructure and elevated temperature mechanical properties of a hypereutectic Al-18Si-4Cu-3Ni piston alloy was investigated. Microstructural observation confirmed that UST effectively refined the sizes of primary Si and intermetallic compounds (e.g. ε-Al3Ni) while promoting their homogeneous distribution. Besides the refinement of the constituent phases, the size of the dendrite arm spacing (DAS), which was hardly affected by UST, significantly deceased with increasing cooling rates. The refinement of the solidification structure in the alloy achieved through both UST and increased cooling rates resulted in an improvement in tensile properties, ultimate tensile strength and elongation in particular, after T5 heat treatment followed by overaging at 350 ℃. However, the elevated temperature yield strength of the alloy was not associated with the refinement, but was rather correlated with the 3-D interconnectivity, morphology and volume fraction of the primary Si. (Received October 21, 2016; Accepted December 7, 2016)