Plastic deformation and fracture behavior of a Fe-modified Al3 Ti-base L12 intermetallic alloy

The microstructure of the ordered intermetallic alloy with a nominal composition of Al66Fe9Ti24 is nearly single-phase L12 structure, with a few second phase agglomerates at some grain corners. Room temperature compression tests showed that this material exhibits a plastic strain of about 11% at fracture. Final fracture of the compression specimens occured by a shear-off process along a surface oriented about 45 degrees to the compression axis. Fractographic analysis revealed that the fracture is transcrystalline and the fracture mode is mainly quasicleavage plus tearing. Transmission electron microscopy (TEM) was used to explore its deformation mechanisms. The dislocation density was low after homogenization, but is greatly increased during deformation. The deformation mode was found to be {110}{111} slip instead of twinning as in Al3Ti. The \u391{110} superdislocations dissociated into two partials of \u391/3(211)-type, bounding a superlattice intrinsic stacking fault (SISF) on the {111} slip plane.Peer reviewed: YesNRC publication: N

Dissociation of dislocations in Al67Mn8Ti26 deformed at ambient and high temperatures

NRC publication: N

Ductility improvement on Al67Ti25Mn8 intermetallic alloy via hot-working

NRC publication: N

The effect of glutamine on Dehydroepiandrosterone-induced polycystic ovary syndrome rats

Abstract Background Previous studies have shown that chronic inflammation and oxidative stress may play an important role in the pathophysiology of polycystic ovary syndrome (PCOS), and glutamine (Gln) have showed the anti-inflammatory and antioxidant properties. So the aim of this study is to investigate the effect of glutamine supplementation on PCOS rats. Methods Female Sprague–Dawley rats were randomly assigned into four groups (n = 10 /group), control group, PCOS group, PCOS+ 0.5 g/kg Gln group and PCOS+ 1.0 g/kg Gln group. All the PCOS rats were administrated with 6 mg/100 g dehydroepiandrosterone (DHEA) for 20 consecutive days, all the PCOS+Gln groups were intraperitoneal injected glutamine twice in the next morning after the last DHEA injection. All the samples were collected 12 h after the last administration. Ovarian histological examinations were analyzed and the concentration of serum hormone, inflammatory and oxidative stress factors were measured. Results There was no obvious ovarian histological change among the PCOS group and PCOS+Gln groups. All the detected inflammation factors [C-reactive protein, interleukin (IL)-6, IL-18, tumor necrosis factor] showed significantly higher in all the PCOS groups compared to the control group (P < 0.01), and were significantly decreased with the supplementation of 0.5 g/kg glutamine (P < 0.01). Concentrations of superoxide dismutase were significantly lower in all the PCOS groups (P < 0.01) compared to the control group, and increased significantly with the supplementation of 0.5 g/kg glutamine (P < 0.01). Serum concentrations of malondialdehyde, nitric oxide synthase and nitric oxide were significantly higher in PCOS group (P < 0.01) compared with the control group, and significantly decreased to the comparative levels of control group with supplementation of 0.5 g/kg glutamine (P < 0.01). Conclusion There is low-grade inflammation and oxidative stress in DHEA-induced PCOS rats. The supplementation of 0.5 g/kg glutamine could effectively ameliorate the inflammation and oxidative stress conditions of PCOS

Abnormal expression of HSP70 may contribute to PCOS pathology

Abstract Background The mechanism of the pathological change of polycystic ovary syndrome (PCOS) is still unclear. Previous studies have shown that PCOS is a chronic nonspecific low-grade inflammatory condition, and that heat shock protein (HSP)70 has a potent anti-inflammatory property. So the aim of this study is to investigate the correlation between HSP70 and the hormones and inflammatory factors and to find out the role of HSP70 in the pathogenesis of PCOS. Methods Twenty female Sprague–Dawley (SD) rats (aged 23 days and weighted 80-90 g) were randomly divided into two groups (n = 10 per group), PCOS group and control group. PCOS group were subcutaneously injected with 6 mg/100 g dehydro-epiandrosterone (DHEA) for 20 consecutive days, the control group were subcutaneously injected with a solvent of equivalent amount. All the samples were collected in the morning fasting state, 12 h after the last administration. Histological examinations of ovarian tissues were analyzed. Hormone levels and inflammatory factors levels were measured by enzyme-linked immunosorbent assay (ELISA) kits. Results Serum concentrations of testosterone (T) and luteinizing hormone (LH) were significantly higher in the PCOS group than the control group (P < 0.001), but the concentrations of estradiol (E2), follicle stimulating hormone (FSH) and insulin didn’t show significant difference between these two groups. All the concentrations of inflammatory factors including C-reactive protein (CRP), interleukin (IL)-6, IL-18, and tumor necrosis factor (TNF)-α. were significantly higher in PCOS group than the control group (P < 0.001). The expressions of HSP70 were significantly lower in serum but higher in ovarian tissues in the PCOS group than the control group. Spearman rank correlation analysis showed strong negative correlation of serum HSP70 levels with T, LH and all the detected inflammatory factors. Conclusion The abnormal expression of HSP70 correlated with testosterone and inflammatory factors, which indicates that HSP70 may play an important role in PCOS pathology

The role of hot-working on the microstructure and mechanical properties of the L12-type manganese-modified Al3Ti alloy

The crystal structure of a manganese-modified Al3Ti intermetallic alloy has been changed from the tetragonal D022 to the L12 cubic structure. The cast alloy shows considerable compression ductility at room temperature. To improve its mechanical properties further, hot-working experiments have been conducted. The results showed that the Al67Mn8Ti25 intermetallic alloy maintains very good hot-workability, the cast alloy can be reduced 60% by a single hot-pressing stroke without cracking. The role of hot-working on the microstructure and the mechanical properties of the alloy have been studied. It was found that the hot-worked alloy shows a deformed structure and some work-hardening after hot-working. Experiments indicated that the starting temperature for recrystallization is about 1173 K and complete recrystallization of the deformed alloy occurs at about 1273 K. Good hot-workability and a high recrystallization temperature permit potential for elevated temperature use. A transmission electron microscopy study on the evolution of dislocation structures in the recovery and recrystallization processes is also reported.Peer reviewed: YesNRC publication: Ye

Deformation and dislocation structure in L12 titanium trialuminide alloys

The deformation behaviour and the nature of dislocations of the Al3Ti-base L12 alloya modified with Fe and Mn etc, were investigated. The results show that the deformation and fracture character istics are closely related to the alloy compositions. The effect of hot-working process on the room tem perature ductility is remarkable, not only resulting in an appreciable improvement of compressive properties but also showing a 0.28% plastic strain in tensile test. The SISF dissociation of a < 110>dislocations on {111} planes was found at room temperature. The determined dissociation scheme is consistent with the mechanical behaviour of these alloys in the lower temperature region.NRC publication: N