Study on Fracture Analysis of (a+~) Dual Phase Stainless Steel Using X-ray Diffraction

In this study, X-ray fractography’)-‘) technique was applied to the (GZ+~) dual phase stainless steel. Effect of the rolling direction on fatigue properties was discussed. Residual stress near the surface was measured by using X-ray diffraction method to the depth direction. Relations between X-ray parameter and fracture mechanics parameter were examined. As the result, distribution of the phase stress in the ferrite phase was related with the maximum stress intensity factor divided by the 0.2% proof stress. INTRODUCTION X-ray diffraction observation4) of metal fractures provides us with useful information on the mechanisms and mechanical conditions of fracturing. This method has been developed especially as an engineering tool for fracture analysis. In the present paper, X-ray fractogarphy technique is applied to fatigue fracture surface of dual phase stainless steel which is used for chemical plant and the oil pipes5). Dual phase stainless steel is a composite material which consists of ferrite (a-Fe) and austenite (y-Fe) phases. This material excels in corrosion-resistance in the chlorinated environment. Many researchers studied the dual stainless steels such as; studies on the influence of the volume fraction of austenite phase6j7), material structure8)9) and aging lo) of the material on the fatigue strength; the fatigue strength of the welded section “I; the microscop ic observation of the initial fatigue crack12); the crack growth property”) 14) under both normal and corrosion conditions’5). However, studies using the X-ray fractography technique on dual phase stainless steels have not been done. In this study, fatigue tests of the dual phase stainless steels were conducted by using compact tension (CT) specimens. X-ray fractography technique was applied on the fatigue fracture surface of the material. In addition, influence of rolling direction on the fatigue mechanism of the material was discussed. Copyright(c)JCPDS-International Centre for Diffraction Data 2001,Advances in X-ray Analysis,Vol.44 62 Copyright(c)JCPDS-International Centre for Diffraction Data 2001,Advances in X-ray Analysis,Vol.44 62