Quantitative and qualitative relationship between microstructural factors and fatigue lives under load- And strain-controlled conditions of Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) fabricated using a 1500-ton forging simulator

The fatigue lives of forged Ti-17 using a 1500-ton forging simulator subjected to different solution treatments and a common aging treatment were evaluated under both load- and strain-controlled conditions: high and low cycle fatigue lives, respectively. Then, the tensile properties and microstructures were also examined. Finally, the relationships among fatigue lives and the microstructural factors and tensile properties were examined. The microstructure after solution treatment at 1203 K, which is more than the β transus temperature, and aging treatment exhibits equiaxed prior β grains composed of fine acicular ¡. On the other hand, the microstructures after solution treatment at temperatures of 1063, 1123, and 1143 K, which are less than the β transus temperature, and aging treatment exhibit elongated prior β grains composed of two different microstructural feature regions, which are acicular α and fine spheroidal α phase regions. The 0.2% proof stress, σ₀.₂, and tensile strength, σB, increase with increasing solution treatment temperature up to 1143 K within the (α + β) region, but decrease with further increasing solution treatment temperature to 1203 K within the β region. The elongation (EL) and reduction of area (RA) decrease with increasing solution treatment temperature, and it becomes nearly 0% corresponding to a solution treatment temperature of 1203 K. The high cycle fatigue limit increases with increasing solution treatment temperature up to 1143 K, corresponding to the (α + β) region. However, it decreases with further increase in the solution treatment temperature to 1203 K in the β region. The fatigue ratio in high cycle fatigue life region is increasing with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase, and it relates well qualitatively with the volume fraction of the primary α phase when the solution treatment temperature is less than the β transus temperature. The low cycle fatigue life increases with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase. The low cycle fatigue life relates well quantitatively with the tensile true strain at breaking of the specimen and the volume fraction of the primary α phase for each total strain range of low cycle fatigue testing.Niinomi M., Akahori T., Nakai M., et al. Quantitative and qualitative relationship between microstructural factors and fatigue lives under load- And strain-controlled conditions of Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) fabricated using a 1500-ton forging simulator. Materials Transactions 60, 1740 (2019); https://doi.org/10.2320/matertrans.ME201904

The stabilizing role of itinerant ferromagnetism in inter-granular cohesion in iron

We present a simple, general energy functional for ferromagnetic materials based upon a local spin density extension to the Stoner theory of itinerant ferromagnetism. The functional reproduces well available ab initio results and experimental interfacial energies for grain boundaries in iron. The model shows that inter-granular cohesion along symmetric tilt boundaries in iron is dependent upon strong magnetic structure at the interface, illuminates the mechanisms underlying this structure, and provides a simple explanation for relaxation of the atomic structure at these boundaries.Comment: In review at Phys. Rev. Lett. Submitted 23 September 1997; revised 16 March 199

Heterogeneous Nucleation of Protein Crystals on Fluorinated Layered Silicate

Here, we describe an improved system for protein crystallization based on heterogeneous nucleation using fluorinated layered silicate. In addition, we also investigated the mechanism of nucleation on the silicate surface. Crystallization of lysozyme using silicates with different chemical compositions indicated that fluorosilicates promoted nucleation whereas the silicates without fluorine did not. The use of synthesized saponites for lysozyme crystallization confirmed that the substitution of hydroxyl groups contained in the lamellae structure for fluorine atoms is responsible for the nucleation-inducing property of the nucleant. Crystallization of twelve proteins with a wide range of pI values revealed that the nucleation promoting effect of the saponites tended to increase with increased substitution rate. Furthermore, the saponite with the highest fluorine content promoted nucleation in all the test proteins regardless of their overall net charge. Adsorption experiments of proteins on the saponites confirmed that the density of adsorbed molecules increased according to the substitution rate, thereby explaining the heterogeneous nucleation on the silicate surface

Effect of microstructure on tensile properties of Ti-17 alloys forged using a 1500-ton forging simulator

Microstructure dependence on mechanical properties were investigated for Ti-17 forged at temperatures between 700 and 850 ˚C with deformation ratio from 33 to 80 %, and solutiontreated at 800˚C for 4 hours and aged at 620 ˚C for 8 hours. The microstructure was observed after solution and aging treatments. The volume fraction and the size of the primary alpha phase was controlled by solution treatment temperature, not forging temperature and deformation ratio. Forging temperature affected the morphology of grain boundary (GB) alpha phase. Deformation ratio affected the grain size and the aspect ratio of the horizontal and vertical grain size of the prior beta phase. The tensile strength was investigated at room temperature, 450, and 600 ˚C. Forging temperature and deformation ratio did not affect the tensile strength because there is no large difference of the volume fraction of the alphaphase. On the other hand, the elongation and the reduction of area increased with increase of the aspect ratio of the prior beta grains; that means, increase of the deformation ratio. Raising of forging temperature also increased elongation and reduction of area due to the film-like GB alphaphase

Effect of microstructure on tensile properties of Ti-17 alloys forged using a 1500-ton forging simulator

Microstructure dependence on mechanical properties were investigated for Ti-17 forged at temperatures between 700 and 850 ˚C with deformation ratio from 33 to 80 %, and solutiontreated at 800˚C for 4 hours and aged at 620 ˚C for 8 hours. The microstructure was observed after solution and aging treatments. The volume fraction and the size of the primary alpha phase was controlled by solution treatment temperature, not forging temperature and deformation ratio. Forging temperature affected the morphology of grain boundary (GB) alpha phase. Deformation ratio affected the grain size and the aspect ratio of the horizontal and vertical grain size of the prior beta phase. The tensile strength was investigated at room temperature, 450, and 600 ˚C. Forging temperature and deformation ratio did not affect the tensile strength because there is no large difference of the volume fraction of the alphaphase. On the other hand, the elongation and the reduction of area increased with increase of the aspect ratio of the prior beta grains; that means, increase of the deformation ratio. Raising of forging temperature also increased elongation and reduction of area due to the film-like GB alphaphase

Quantitative relationship between microstructural factors and fatigue life of Ti-5Al-2Sn-2Zr-4Cr-4 Mo (Ti-17) fabricated using a 1500-ton forging simulator

The microstructures, tensile properties, and fatigue lives of the forged Ti-17 using a 1500-ton forging simulator subjected to different solution treatments and a common aging treatment under both load- and strain-controlled conditions to evaluate high cycle fatigue and low cycle fatigue lives, respectively were examined. Then, the tensile properties, microstructures, and relationships between fatigue lives and the microstructural factors were discussed. The fatigue limit under load-controlled conditions increases with increasing solution treatment temperature up to 1143 K, which is in the (α + β) region. However, it decreases with further increase in the solution treatment temperature to 1203 K in the b region. The fatigue ratio at fatigue limit is increasing with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase, and it relates well qualitatively with the volume fraction of the primary α phase when the solution treatment temperature is less than the b transus temperature. The fatigue life under strain-controlled conditions to evaluate the low cycle fatigue life increases with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase. The fatigue life under strain-controlled conditions to evaluate the low cycle fatigue life relates well quantitatively with the tensile true strain at breaking of the specimen and the volume fraction of the primary α phase for each total strain range