Browsing by Author "Tsay, GowDong"

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A New Austenitic FeMnAlCrC Alloy with High-Strength, High-Ductility, and Moderate Corrosion Resistance
(2010-12-01)
Tsay, GowDong
;
Lin, ChihLung
;
Chao, ChuenGuang
;
Liu, TzengFeng
;
材料科學與工程學系
In this study, a new austenitic Fe-28%Mn-9%Al-6%Cr-1.8%C (in mass%) alloy is developed. Because the alloy contains a high density of fine (Fe,Mn)(3)AlC carbides within the austenite matrix, the alloy in the as-quenched condition exhibits an excellent combination of strength and ductility comparable to that of the aged FeMnAlC alloys. In addition, owing to the formation of a layer of Cr and Al oxides in the passive film formed on the alloys, the corrosion potential E(corr) (-538 mV) and the pitting potential E(pp) (-25 mV) of the present alloy in 3.5% NaCl solution are considerably higher than the E(corr) (-920 similar to-789 mV) and E(pp) (-500 similar to-240 mV) values of the as-quenched and aged FeMnAlC alloys. Whereas the tensile strength of the present alloy is almost the same as that of conventional AISI 410 martensitic stainless steel, the present alloy possesses superior ductility than AISI 410 martensitic stainless steel. Furthermore, in 3.5% NaCl solution, the E(pp) (-25 mV) of the present alloy is noticeably higher than that (-250 similar to-100 mV) of the conventional AISI 410 martensitic stainless steel. These results indicate that the present alloy in the as-quenched condition can possess high-strength and high-ductility as well as moderate corrosion resistance. [doi:10.2320/matertrans.M2010199]
Effect of Carbon on Spinodal Decomposition in Fe-26Mn-20Al-C Alloys
(2011-03-01)
Tsay, GowDong
;
Tuan, YiHsuan
;
Lin, ChihLung
;
Chao, ChuenGuang
;
Liu, TzengFeng
The supersaturated austenite (gamma) phase decomposed into fine C-rich ordered k' particles and C-depleted gamma(0) phase during quenching in alloys with 5.5 <= C <= 8.0 at%. The misfit between k' particles and gamma(0) phase decreased with increasing carbon content. The strain energy increased dramatically as carbon content approached slightly below 5.5 at%. Undercooling may be insufficient to overcome the strain energy effects, thus leading to the absence of spinodal decomposition and k' particles in the present and prior austemtic FeMnAlC alloys with 3.1 <= C <= 5.2 at% under the as-quenched condition. Additionally, both the amount of ordered k' particles and the carbon concentration in the k' particles increased with increasing carbon content of the alloy. These results revealed that a higher degree of carbon supersaturation in the initial gamma phase might promote a tendency toward C-rich k' particle formation during quenching. [doi:10.2320/matertrans.M2010255]
Phase Separation from L2(1) to (B2+L2(1)) in Fe-24.6Al-7.5Ti Alloy
(2010-10-01)
Tsay, GowDong
;
Su, ChunWei
;
Tuan, YiHsuan
;
Chao, ChuenGuang
;
Liu, TzengFeng
As quenched microstructure of the Fe 24 6 at% Al 7 5 at% Ti alloy was a mixture of (A2+L2(1)) phases When the as quenched alloy was aged at 1173 K for moderate times the L2(1) domains grew considerably and B2 phase was formed at a/2(100) anti phase boundaries (APBs) as well as phase separation from well grown L2(1) to (B2+L2(1)*) occurred basically contiguous to the APBs where L2(1)* is also a L2(1) type phase With continued aging at 1173K the phase separation would proceed toward the whole well grown L2(1) domains This microstructural evolution has not been reported in the Fe Al Ti alloy systems before [doi 10 2320/matertrans M2010167]