Deformation and fracture behavior of 316L sintered stainless steel under various strain rate and relative sintered densi
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316L sintered stainless steel is an important structural material because it possesses a good combination of strength, toughness, and stress corrosion cracking resistance. Due to its unique combination of properties, 316L sintered stainless steel has been adopted for a wide range of applications in the automobile, aerospace, nuclear, and defense industries.[1,2] During their service life, or during some stages of their manufacture, 316L sintered stainless steel components may be intentionally or inadvertently subjected to high strain rates, resulting in a deformation response significantly different from that observed at lower strain rates. It is well known that the mechanical strength and fracture response of powder metallurgy (P/M) parts are strongly influenced not only by the loading rate, but also by their chemical composition and sintered density. Because 316L sintered stainless steel is sensitive to densification processing and to the deformation conditions, understanding the variation of its mechanical performance as a function of the sintered density and strain rate is of major concern to engineers and designers. In order to develop 316L sintered stainless steel with enhanced properties in high loading rate service environments, it is important to quantitatively characterize the effects of the sintered density and the strain rate on its dynamic deformation behavior, microstructural evolution, and fracture response. WOEI-SHYAN LEE, Professor, and CHIEN-CHENG CHIU, Graduate Student, are with the Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan. Contact e-mail: wslee@mail. ncku.edu.tw Manuscript submitted November 8, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
The mechanical properties of 316L sintered stainless steel have generally been characterized in terms of quasistatic deformation.[3,4] Some investigations into the corrosion behavior and densification behavior of 316L sintered stainless steel also exist in the literature.[5,6] The influence of the microstructure on fatigue crack propagation in sintered stainless steels has been reported,[7] and the effects of thermocapillary forces during the molding of 316L type powder metallurgy austenitic stainless steels have been assessed.[8] Although these studies have investigated the fundamental properties of 316L sintered stainless steel, the literature contains very little systematic data relating to the influence of the sintered density on its strength, microstructure, and fracture response, particularly under high strain rate loading. The mechanical properties of materials are known to change under different strain-rate loading conditions. For example, in many metals and alloys,[9–13] the flow stress is typically much higher at high strain rates than at low strain rates. Furthermore, a rapid increase in the strain rate sensitivity at strain rates above 103 s1 has been reported.[14,15] This rate-dependent behavior can be attributed to different rate controlling mechanisms. The difference in strain rate sensitivity between
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