本論文研究鐵-30.2錳-1.72鋁-0.99碳( wt% )合金鋼的相變化。合金經1100℃固溶處理再經800至500℃之時效處理後，於沃斯田體的晶界處有共存的M3C與M23C6碳化物。當於溫度為600℃以下的時效處理，有層狀的波來體組織生成。M3C與M23C6碳化物亦可以各以層狀波來體組織的方式，共同存在於沃斯田體晶粒內。
於M3C碳化物組成的波來體組織中， M3C碳化物與鄰近的BCC肥粒體晶粒之間，具有未曾被發現過的二組新方位關係：第一組為：[-100]C//[-1-1-1]α ; (031)C//(10-1)α及(011)C//(11-2)α。而第二組為：[111]C//[-1-1-1]α; (-211)C//(0-11)α及(-110)C//(1-21)α。
M23C6碳化物所組成之層狀波來體，其初析M23C6碳化物是先於沃斯田體的晶界處成核，其與其旁的沃斯田體有立方晶對立方晶的方位關係。當此M23C6碳化物成長時，其主要之成長方向卻是往未有方向關係之沃斯田體晶粒內成長，其旁伴隨著肥粒體晶粒的成核與成長，而此肥粒體與M23C6碳化物間亦保持有方位關係。故以上三種晶體間皆有方位關係，目前已確定(110)α//(1-11)C6//(1-11)γ。
合金於800及750℃的時效處理後，層狀排列的M3C碳化物於沃斯田體晶粒內分佈，此情形類似於析出反應中之層狀反應。飽和狀態的沃斯田體晶粒(γ’)，藉由M3C碳化物的析出以成為穩定的沃斯田體狀態(γ)。而M3C碳化物以層狀方式往晶粒內成長，其結構是由M3C碳化物以層狀形貌分佈於沃斯田體相的晶粒內，其於金相的觀察亦顯示為似波來體的層狀組織。

This aim of the thesis is to study the phase transformations of a steel with the composition of Fe-30.2Mn-1.72Al-0.99C(wt%). The heat treatments included solution heat treatment at 1100℃ and aging at low temperatures ranging from 800 to 500℃. M3C and M23C6 carbides coexist at austenitic grain boundaries. Pearlite formed. M3C and M23C6 carbides coexist at different pearlite structures after the alloy was aged at temperatures under 600℃.
In a pearlite phase comprised of M3C carbide, there are two new orientation relationships between the M3C carbide and ferrite. The first one is [-100]C//[-1-1-1]α; (031)C//(10-1)α and (011)C//(11-2)α. The second one is [111]C//[-1-1-1]α; (-211)C//(0-11)α and (-110)C//(1-21)α.
For the pearlite layer phase composing of both M23C6 carbide and ferrite, the pro-eutectoid M23C6 carbide nucleated at austenitic grain boundaries with a cubic to cubic orientation relationship with one of the neighbor FCC grains. This M23C6 carbide grew into the FCC grain without the orientation relationship. The layer ferritic grain formed besides the M23C6 carbide. We found that there is an orientation relationship (110)α//(1-11)C6//(1-11)γ among the three different grains.
We observed cellular precipitation of M3C carbide within the austenitic grains for alloy specimens being aged at 800 and 750℃. This is a special type of precipitate reactions.

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