The present study is concerned with effects of microstructural factors such as distribution and fraction of coarse carbides located along solidification cell boundaries and characteristics of tempered martensitic matrix on fracture properties of five high speed steel (HSS) rolls manufactured by a centrifugal casting method. In situ microfracture observation, fracture toughness measurement and fractographic observation were conducted on these rolls to clarify fracture mechanisms. The in situ observation results indicated that coarse carbides located along cell boundaries provided easy intercellular fracture sites under a low stress intensity factor level. In the rolls whose intercellular carbide fraction and matrix hardness were high, fracture easily occurred under a low stress intensity factor. On the contrary, in the rolls where a small amount of intercellular carbides was distributed on the relatively ductile matrix of lath tempered martensite, the fracture path was accompanied by a considerable amount of plastic deformation including shear band formation, thereby resulting in high fracture toughness. In order to obtain better microstructure, hardness and fracture toughness of the HSS rolls, the minimisation of intercellular carbides, the refinement of carbides and the improvement of the matrix characteristics by controlling alloying elements and heat treatment conditions were suggested.
Microstructural characterization and aging hardening behaviors of a new designed Ti-12.1Mo-1Fe alloy during solution treatment and aging were investigated in the present study. It is well known that when β-Ti alloys are generally under solution treatment or aging, α phases and ω phases appear or disappear dependent on heat treatment temperature and holding time. It is very necessary to understand the phase transformation phenomenon and to control the microstructure because these phases can control the drastic changes of the mechanical and physical properties of these alloys. According to the calculated [Mo]eq value and the microstructural observation, the β-transus temperature was about 780• . After the solution treatment, this alloy was composed of the β-phase and the microstructure mainly consisted of the equiaxed β grains with the average size of 25 µm. ω phases which were precipitated during aging process, played a more important role to the hardening effect than α phases. The highest hardness value of Ti-12.1Mo-1Fe alloy showed in the condition of the aging temperature of 450• . The hardening due to ω-phase precipitation can lead to a high hardness about 480 Hv but the coarse α-phase result in hardness below 300 Hv.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.