史賓諾多新沃斯田鐵型鐵錳鋁碳合金之軋板和鑄件氮化處理、相變化、機械性質與抗腐蝕性研究

Abstract

五十年來γ-FeMnAlC合金研究均集中在0.7≦C≦1.3wt.%，固溶狀態(SHT)為單一γ相。眾多學者發 現，經550℃ 15~16小時時效可得最佳強度和延性組合(Y.S.:1094MPa, El.:26%)，強化因細密κ'-carbides 時效時在γ內析出。近年來，我們發現1.5≦C≦2.0wt.% FeMnAlC在淬火過程中藉史賓諾多相分解 （Spinodal Decomposition;SD）在γ內產生緻密奈米級κ'(~10nm)。此重大發現在學術和應用上均有豐碩 成果：(1)SHT下已有κ'-carbides，經450℃ 9~12小時時效，其 YS: 1119~1423MPa,和El: 40.3~25.8%。 在相同El下，強度比C≦1.3wt.%高30%；且強度和延性組合遠超過2012年美國能源部和鋼鐵協會宣佈 2017~2025年欲達到的第三代高強度鋼材(3GAHSS)之強度和延性組合。(2)首度發現：多晶金屬 「Bursting Dislocation Nucleation」之塑性變形機制。(3)首度觀察到Taylor lattice原子排列影像。 (4)2010~2012年成功開發前所未有「高強度、高延展性以及高耐腐蝕性鐵錳鋁碳合金」2012年申請台 灣、大陸和美國專利；此專利已技轉成立新公司。表面硬度、基材強度和延性及耐腐蝕性均遠優於經 最佳氮化後各類合金鋼、不銹鋼、工具模具鋼。(5)技轉高爾夫球桿，其中Power BILT 品牌，2007年 獲日本最佳鐵桿金質獎。(6)2009年製作國防部「高性能防護鋼板」，遠高最新抗彈FJ(SS109)規範。 本計畫第一至第三年主要研究目標分別：(1)探討SD-FeMnAlC合金最佳離子和氣體氮化條件； (2)SD-FeMnAlC基材和經最佳氮化處理後之低溫機械性質，和(3)SD-FeMnAlC鑄件經熱處理和氮化處 理後之各種性質。其詳細請參考本計畫研究目的內容。

Over the last 5 decades, most of the researches in austenitic FeMnAlC alloys have been focused on the alloy systems with 0.7C1.3 wt.%. In as-quenched condition, the microstructure is single austenite phase. For these alloys, the optimal combination of strength and ductility (YS: 1094 MPa; El: 26%) can be obtained after aging at 550 C for 1516 hrs. The primary strengthening mechanism is due to the precipitation of high density fine '-carbides formed within the austenite matrix during aging. Recently, we discovered for the first time that, for FeMnAlC alloys with 1.5C2.0 wt.%, a high density of nanosized (10 nm) '-carbides is formed within the austenite matrix by spinodal decomposition during quenching. This discovery has led to significant impacts to both academic and application aspects: (1) Since the '-carbides already exist in the as-quenched alloys, both the aging time and temperature for obtaining the optimal combination of strength and ductility can be significantly reduced. For instance, after aging at 450 C for 912 hrs, the obtained YS reaches 11191423 MPa and the El maintains to be 40.325.8%. Under the same elongation, our results showed over 30% enhancement in strength as compared with the aged C1.3 wt.% FeMnAlC alloys. More importantly, the obtained strength-ductility combination has evidently exceeded by a sizeable margin over the targeted specifications put forth by the US DOE in 2012 and by American Steel Association for the third generation advanced high-strength steels (3GAHSS) to be on market in 20172025. (2) We discovered, for the first time, a novel deformation mechanism in polycrystalline metals which is governed by “bursting dislocation nucleation”. (3) We are the first to directly observe the dislocation Taylor lattice in atomic resolution images. (4) Based on these pioneer research results, we have successfully developed unprecedented “high-strength, high-ductility and high corrosion resistance FeMnAlC alloys”, which had been filed in for patent applications in US, Taiwan and Mainland China. These alloys exhibit far superior surface hardness, matrix mechanical strength and ductility, and corrosion resistance as compared to all of the optimally nitrided alloy steels, stainless steels, and tool steels. Moreover, the patent has been transferred to a newly founded company. (5) We also successfully transferred the technology to several golf club companies. One of them with the brand name of Power BILT won the Japanese Golden Quality Award in 2007. (6) In 2009, we also prepared the high performance protective steel plate for the Ministry of Defense, which showed properties far better than the FJ (SS109) specifications for bullet resistance. The main research goals of the present proposal for the next three years are, respectively: (1) first year: investigate the optimal ion and gas nitriding conditions for the spinodal decomposition FeMnAlC alloys (SD-FeMnAlC); (2) second year: study the low-temperature mechanical properties of both the pristine and optimally nitrided SD-FeMnAlC alloys; (3) third year: explore the properties of the as-cast SD-FeMnAlC alloys, including heat-treated and nitrided. For the details, please refer to the main content of the present proposal.