Microstructure Investigation of Thermally Induced Phase Transformation in Fe–Mn– Mo–Si Alloys

Abstract

In this study, structural and crystallographic properties of phase transformations in Fe–Mn– Mo–Si (Mn = 15.14 wt.% and 18.45 wt.%) alloys were investigated. The effects of heat treatment temperature on microstructure were investigated by Scanning Electron Microscopy (SEM) and Metallurgical Microscopy (MM). In addition to this, crystallographic properties of phase transformations were revealed by using Transmission Electron Microscopy (TEM) and X–Ray Diffraction (XRD) methods. In the samples subjected to heat treatment at 750 C, it was observed that bainite structure was formed in the alloy where Mn amount was low and ferrite structure in the alloy where Mn amount was higher. In addition, it was found that both alloys heat–treated at 900 C had the same microstructure (pearlite structure) in SEM and MM microscopy. At the same time, microstructure observations revealed that bainite and pearlite structures contain a mixture of ferrite and cementite. In the TEM studies it was revealed by electron diffraction pattern analyses that bainite and ferrite phase crystallized in b.c.c. structure and cementite phase in orthorhombic structure. → type transformation was observed for –bainite formation, and orientation relationship was found as 〖(1 ̅11)〗_//〖(011)〗_ , 〖[101]〗_//〖[1 ̅11 ̅]〗_.

Keywords

• Bainite
• Ferrite
• Cementite
• Pearlite
• Crystallographic properties
• TEM

Fe-Mn-Mo-Si Alaşımlarında Termal Etkili Faz Dönüşümlerinin Mikro Yapı İncelemeleri

Abstract

Bu çalışmada, Fe-%XMn-Mo-Si (X=15,14 ve 18,45) alaşımlarında termal etki ile meydana gelen faz dönüşümlerinin yapısal ve kristalografik özellikleri incelenmiştir. Isıl işlem sıcaklığının mikro yapısı üzerine etkileri Taramalı Elektron Mikroskobu (SEM) ve Metalürji Mikroskobu (MM) incelemeleri ile yapıldı. Bunun yanı sıra kristalografik özellikleri ise Geçirmeli Elektron Mikroskobu (TEM) ve X-Işınları Kırınımı (XRD) yöntemleri kullanılarak ortaya çıkarılmıştır. 750 C’ de ısıl işleme tabi tutulan numunelerde Mn miktarının az olduğu alaşımda beynit yapı oluşurken Mn miktarının daha fazla olduğu alaşımda ferrit yapının oluştuğu gözlendi. Ek olarak, 900 C'de ısıl işlem görmüş her iki alaşımın da SEM ve MM mikroskopisinde aynı mikro yapıya (perlit yapı) sahip olduğu bulundu. Aynı zamanda, beynit ve perlit yapılarının ferrit ve sementit karışımını içerdiği mikro yapı gözlemleri ile ortaya konuldu. TEM incelemelerinde elektron kırınım deseni analizleri sayesinde beynit ve ferrit fazın b.c.c. yapısında, sementit fazın ise ortorombik yapıda kristalleştiği ortaya konuldu. -beynit oluşumu için  türü dönüşüm gözlendi ve dönme bağımlılığı 〖(1 ̅11)〗_//〖(011)〗_ , 〖[101]〗_//〖[1 ̅11 ̅]〗_ olarak bulundu.

Keywords

• Beynit
• Ferrit
• Sementit
• Perlit
• Kristalografik özellikler
• TEM

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