Evolution of deformation property and strength component mobilization for thermally treated Beishan granite under compression

The cohesion weakening and friction strengthening(CWFS)model for rock reveals the strength components mobilization process during progressive brittle failure process of rock,which is very helpful in understanding mechanical properties of rock.However,the used incremental cyclic loading−unloading compression test for the determination of strength components is very complicated,which limits the application of CWFS model.In this paper,incremental cyclic loading−unloading compression test was firstly carried out to study the evolution of deformation and the strength properties of Beishan granite after various temperatures treated under different confining pressures.We found the axial and lateral unloading modulus are closely related to the applied stress and damage state of rock.Based on these findings,we can accurately determine the plastic strain during the entire failure process using conventional tri-axial compression test data.Furthermore,a strength component(cohesive and frictional strength)determination method was developed using conventional triaxial compression test.Using this method,we analyzed the variation of strength mobilization and deformation properties of Beishan granite after various temperatures treated.At last,a non-simultaneous strength mobilization model for thermally treated granite was obtained and verified by numerical simulation,which demonstrated the effectiveness of the proposed strength determination method.

Effect of synthesis parameters on structural and mechanical properties of Ti_(3)Al-Nb-Mo intermetallic compound obtained by powder metallurgy techniques

The influence of microstructure,heat treatment and alloying addition on mechanical and fracture properties of Ti3Al-basedintermetallic at room and elevated temperatures was studied.Ti3Al?11Nb?1Mo(mole fraction,%)alloy was consolidated viapowder metallurgy processing by mechanical alloying(MA)and hot pressing(HP).MA powders were characterized using XRD andSEM-EDS.Optimum MA duration was25h and HP conditions of1350°C,2h,35MPa.After HP,solution treatment at1050°C for1h and water quenchingα2+βWidmanst?tten microstructure is present,while subsequent aging at800°C during24h induces smallcontent of O-phase.High fraction ofβ-phase is a direct consequence of Mo.Compression tests were performed from roomtemperature to750°C in vacuum.The yield strength of compacts increases with temperature up to250°C(pyramidal slip systemsactivation),after which it decreases.Ductility increases throughout the whole temperature range.The presence of O phasecontributed to ductility increase in aged alloys,while negligibly lowering yield strength.Registered drop in the yield strength of agedalloys compared with non-aged ones was mostly influenced by precipitation ofα″2particles.Mixed fracture modes are operative atall temperatures.

Study on photoluminescence of thermally treated Bi_(12)GeO_(20) and Mo:Bi_(12)GeO_(20) crystals

Photoluminescence (PL) of Bi12GeO20 and Mo doped Bi12GeO20 (Mo: Bi12GeO20) crystals in visible and near-infrared (NIR) spectral regions were studied. X-ray diffraction analysis, absorption and Raman scattering spectra of these crystals were also measured. Pure Bi12GeO20 after annealing in N2 atmosphere at 450 oC and 550 °C show predominant emissions at about 745 and 1250 nm bands, while the emission peaks of Mo:Bi12GeO20 crystals untreated or after annealing in Ar at 300 °C are at around 538 and 1165 nm. The results suggest that annealing induces intrinsic luminescence of Bi in pure Bi12GeO20 at room temperature and Mo influences the luminescence centers of Bi12GeO20. The emission peaks of Bi12GeO20 and Mo: Bi12GeO20 probably owe to lower-valent Bi ions.