Effect of Matrix Microstructure on Creep Properties of Squeeze Cast Magnesium Matrix Composites

Abstract Effect of matrix microstructure on creep behaviors of squeeze cast magnesium matrix composites was investigated. Aluminumborate whisker was used as reinforcement and AZ31, AS52 and Sr added AS52 Mg alloys were used for matrix alloys. The rein-forcement was distributed homogeneously and defect-free composite was manufactured. Creep tests were carried out at the tem-perature of 150 o C under the applied stress of 50 and 100 MPa for Mg alloys and Mg MMCs, respectively. The creep resistance ofMg MMCs was in this order: AS52-Sr > AS52 AZ31 MMCs. Void initiation during creep mainly occurred at Mg/Mg 17 Al 12 interfaceand propagation went along grain boundaries. On the other hand, Mg 2 Si phase was not attributed to the creep void initiation.Key words: Squeeze casting, Mg metal matrix composite, Creep properties, Void initiation.(Received August 4, 2009 ; Accepted August 24, 2009) 1. 서 론 마그네슘 합금은 실용 구조용 재료 중에서 가장 가볍고, 높은 비강도, 진동감쇠능 및 전자파 차폐성과 같은 우수한 고유특성들로 인해 경량화를 통한 연비향상이 기대되어지는 자동차및 항공기 등의 수송기기 부품 소재로서 많은 각광을 받고 있다[1-2]. 현재 마그네슘 합금은 자동차용 스티어링 코어, 시트프레임, 에어백 하우징 등에 본격적으로 적용되기 시작하고 있으며, 대표적인 상용화 합금으로는 Mg-Al-Zn 계열인 AZ91D합금, Mg-Al-Mn 계열인 AM60 합금등이 있다[3]. AZ91 Mg합금은 주조성이 좋으며, Mg