鐵-9鋁-30錳-(1,2)鈦-1碳合金相變化

Abstract

本篇論文是利用光學顯微鏡(OM)和穿透式電子顯微鏡(TEM)，研究 鐵-9.鋁-30.0錳-1.0碳合金的相變化。將這兩種合金在1050℃~1250℃溫度間沃斯田鐵化後淬火，其顯微結構為沃斯田鐵相與TiC碳化物相的混合。在之前的研究中知道，儘管在液相線下面增加沃斯田鐵化溫度到1250℃, 並不能把有極高熔點的矩形TiC碳化物在兩種合金中溶解在沃斯田鐵基材裡。這種TiC碳化物具有B1-型結構，其晶格常數為0.443 nm。沃斯田鐵相及TiC碳化物相間的方向關係為(100)TiC//(100)γ和(110)TiC//(110)γ，有著立方對立方的方向關係。電子顯微鏡觀察顯示(Fe, Mn, Ti)3AlCx碳化物的存在溫度會因鈦含量的增加而被降低。 因此,得出如下結論, 對鐵-鋁-錳-碳合金而言，增加鈦這種容易形成碳化物元素的含量 ,會使得(Fe, Mn, Ti)3AlCx碳化物的相存在區間明顯的被壓縮。

Phase transformations in Fe-9.0wt.%Al-30.0wt.%Mn-1.0 wt.%C alloys with 1.0 wt.% and 2.0 wt.% Ti have been investigated by means of optical microscopy and scanning transmission electron microscopy. In the present study, it was found that even the austenitizing temperature was increased to 1250℃, just below the liquidus, the rectangular TiC carbides could not be completely dissolved within the austenite matrix in both alloys. The TiC carbide has an B1-type structure with lattice parameter a = 0.443 nm. Therefore, when both of the alloys were austenitized at a temperature range from 1050℃to 1250℃ and then quenched, the microstructures was austenite phase containing retained TiC carbides. The orientation relationship between the TiC carbide and the austenite phase was determined to be (100)TiC//(100)γ and (110)TiC//(110)γ, which corresponds to the cubic to cubic orientation relationship. Transmission electron microscopy examinations also indicated that the existing temperature of the (Fe, Mn, Ti)3AlCx carbides would be lowered with increasing the titanium addition. Therefore, it is concluded that owing to the addition of the strong carbide-forming element of titanium to the Fe-Al-Mn-C alloys, the (Fe, Mn, Ti)3AlCx carbide phase-field region would be pronouncedly compressed.