Surface grain refinement mechanism of SMA490BW steel cross joints by ultrasonic impact treatment

Ultrasonic impact treatment (UIT) is a postweld technique for improving the fatigue strength of welded joints. This technique makes use of ultrasonic vibration to impact and plastically deform a weld toe and can achieve surface grain refinement of the weld toe, which is considered as the main reason for the improvement of fatigue strength. In this paper, the microstructure of the surface of a treated weld toe was observed by metallographic microscopy and transmission electron microscopy (TEM). The results show that UIT could produce severe plastic deformation on the surface layer of the weld toe and the maximum depth of plastic deformation extended to approximately 260 μm beneath the treated surface. Repeated processing could exacerbate the plastic deformation on the surface layer, resulting in finer grains. We can conclude that the surface grain refinement mechanism of SMA490BW welded joints is related to the high density of dislocation tangles and dislocation walls. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Brazeability evaluation of Ti-Zr-Cu-Ni-Co-Mo filler for vacuum brazing TiAl-based alloy

Ti-47Al-2Nb-2Cr-0.15B(mole fraction,%)alloy was vacuum brazed with amorphous and crystalline Ti.25Zr-12.5Cu-12.5Ni-3.0Co-2.0Mo(mass fraction,%)filler alloys,and the melting,spreading and gap filling behaviors of the amorphous and crystalline filler alloys as well as the joints brazed with them were investigated in details.Results showed that the amorphous filler alloy possessed narrower melting temperature interval,lower liquidus temperature and melting active energy compared with the crystalline filler alloy,and it also exhibited better brazeability on the surface of the Ti.47Al.2Nb.2Cr.0.15B alloy.The TiAl joints brazed with crystalline and amorphous filler alloys were composed of two interfacial reaction layers and a central brazed layer.Under the same conditions,the tensile strength of the joint brazed with the amorphous filler alloy was always higher than that with the crystalline filler alloy.The maxmium tensile strength of the joint brazed at 1273 K with the amorphous filler alloy reached 254 MPa.

Rhizoma Drynariae Improves Endometrial Receptivity in a Mus Model of Dysfunctional Embryo Implantation

Background: Rhizoma drynariae is a traditional Chinese medicine used in orthopedics and traumatology, but its effect on endometrial receptivity remains unknown. Aims and Objectives: To observe effect of Rhizoma drynariae and its main components on endometrial receptivity in a mus model of dysfunctional embryo implantation. Materials and Methods: Mus models were established by the Gn RHa+HMG+HCG method. Normal mus receiving saline were used as controls and the remaining six groups were: model receiving saline, progynova, aspirin, Rhizoma drynariae, osteopractic total flavone, and naringin. Pinopodes in uterine endometrium were examined by scanning electron microscopy. Stem cell factor(SCF) m RNA expressions was determined by real-time RT-PCR, and estrogen receptor α(ERα), progesterone receptor(PR) by immunohistochemistry. Results: In the model group, surface morphology of endometrium was heterogeneous, without obvious pinopodes. In the Rhizoma drynaria and progynova groups, pinopodes were abundant. Compared with the blank group, model group had lower levels of SCF(-47%), ERα(-63%) and PR(-50%)(all P<0.05). In comparison, Rhizoma drynariae group had higher levels of SCF(+73%), ERα(+118%) and PR(+101%)(all P<0.01). The individual main components of Rhizoma drynariae had variable efficacy. Conclusion: Rhizoma drynariae could improve endometrial receptivity of mouse models of dysfunctional embryo implantation as shown by increased numbers of pinopodes and higher levers of SCF, ERα, PR compared with the model group.