熱浸鍍鋅-鋁-鎂三元合金鍍層鋼板之微結構、高溫氧化與電化學行為

Abstract

先進高強度鋼與熱衝壓製程相輔相成應用，是目前車廠為落實車體減輕策略的方法。為保護鋼底材脫碳與氧化，且讓鋼材有一定障蔽保護與犧牲保護之效果，鋅基合金鍍層是當代對於熱衝壓製程開發必要發展。 三元鋅基合金鍍層之開發與運用評估更是鮮少的研究主題。本研究使用商用鋅鋁鎂三元合金鍍層，鍍層成分為6Al-3Mg-Zn與11Al-3Mg-Zn，進行鋅-鋁-鎂三元合金鍍層之鍍層微結構，以及沃斯田體化之後鍍層演變，進而影響其後續電化學行為的抗蝕能力，進行一系列評估，了解三元鍍層對於熱衝壓製程之可靠性。 實驗結果發現，熱浸鍍鋅-鋁-鎂三元合金鍍層系統中，在11Al-3Mg-Zn合金鍍層中，在沃斯田體化後會有有別於過往的鍍層結構。在底材與鍍層介面產生一連續的鐵鋁相，該鐵鋁相除了有效的避免液態鋅屬脆化的問題之外，也可以抑制鋼底材鐵原子的擴散，使鍍層內的鋅含量提高，可以有效的提升整體鍍層之障蔽保護與犧牲保護的效果。

Advanced high strength steel and hot stamping process are used complementarily for the demand of vehicle facilities to reduce the vehicle weight. To protect the steel substrate from decarbonizing and oxidizing and ensure that the steel substrate has enough effect of barrier and sacrificial anode protection, it is necessary to develop Zn-based coatings on steels for the hot stamping process. The development and application estimation of ternary Zn-based coatings are rarely research topic. In this study, different compositions of 6Al-3Mg-Zn and 11Al-3Mg-Zn, microstructure and phase evaluation after austenitizing of Zn-Al-Mg ternary coatings on steel and electrochemical behavior which affects the corrosion resistance are studied. It was estimated to understand the reliability for the hot stamping process. The result shows that there are different microstructures of Zn-Al-Mg coatings after austenitizing when the Al/Mg ratio is high in the ternary coating system. Continuous Fe-Al phase layers form between the coatings and the steel substrate. This Fe-Al phase not only avoids liquid metal enbrittlement but also restrains the Fe atoms from diffusing to the coatings so that the Zn content increases and enhance the barrier and sacrificial anode protection effectively.