Mn和V对TiAl合金热腐蚀的影响

Mn和V对TiAl金属间化合物在900℃(Na,K)_2SO_4熔盐中热腐蚀行为的影响有所不同。TiAl合金中加入Mn后,最外层的腐蚀产物为以Al_2O_3为主、另有少量TiO_2的混合物;内层是Al,Ti和Mn的混合氧化物以及Ti的硫化物,加Mn在一定程度上减弱了TiAl合金的耐蚀性。TiAl和TiAl-Mn合金中加入V后耐蚀性明显变差,最外层腐蚀产物以TiO-2为主,并含有少量Al_2O_3和微量的V_2O_5,腐蚀层中的V_2O_5引起Al_2O_3的酸性溶解,因而不能形成保护性的Al_2O_3层,形成的TiO_2和Al_2O_3混合膜的黏附性差,较易剥落。

Effect of high magnetic field on phase transformation temperature and microstructure of Fe-based Alloys

The effect of a high magnetic field up to 30T on phase transformation temperature and microstructure of Fe-based alloys has been reviewed. A high magnetic field accelerates ferrite transformation, changes the morphology of the transformed microstructures and increases the A3 and A1 temperature. In a magnetic field of 30T, the A1 temperature increases by about 37.1℃ for Fe-0.8C, the A3 temperature for pure Fe increases by about 33.1℃. The measured transformation temperature data are not consistent with calculation results using Weiss molecular field theory. Ferrite grains are elongated and aligned along the direction of magnetic field in Fe-0.4C and Fe-0.6C alloys by ferrite transformation, but elongated and aligned structure was not found in pure Fe, Fe-0.05C alloy and Fe-1.5Mn-0.11C-0.1V alloy.

微结构对中碳马氏体钢纳米硬度分布的影响

利用纳米力学探针对传统的淬火-回火中碳马氏体钢的微观硬度分布进行了评价.在1000μN载荷下,硬度的标准偏差与平均值之比为15.4%,而在9.8N下的维氏硬度该比值为1.5%.结合电子背散射分析和扫描电子显微镜观察表明,纳米硬度值的分散并非主要来源于马氏体板条的晶体取向,而是由于在亚微米尺度上微结构(如渗碳体的分布)的不均匀造成的.对具有不同取向的钨单晶(001),(101)和(111)的纳米力学探针测量表明,晶体取向造成的纳米硬度值分散性很小.对另一种具有相同化学成分但经过热轧变形导致渗碳体分布更加细小而均匀的马氏体钢的纳米力学探针测量表明,其纳米硬度值分散性比传统的马氏体钢要小得多.这两个结果都进一步佐证了上述结论.