Corrosion and wear behaviors of Al-bronzes in 5.0% H_2SO_4 solution

Steady-state corrosion and wear behaviors of two Al-bronzes,Cu-14Al-X and QAl9-4,in 5.0% H2SO4 solution were investigated. It is found that wear loss of bronzes in 5.0% H2SO4 solution is lower than that in water or in air,namely,it exhibits negative synergy between corrosion and wear. Further analysis shows that corrosive solution plays an important role in cooling of specimen during the sliding wear to prevent the reduction of the surface hardness of specimen,induced by frictional heat. On the other hand,the bronzes suffer a de-alloying corrosion,and a noble copper subsurface and patina form on the specimen surface in corrosive solution,which has a passive function for further corrosion. The noble copper subsurface experiences strain hardening during the corrosion and wear,resulting in the increase of the surface hardness thus the increase in wear resistance.

Convection effect on dendritic growth using phase-field method

Phase-field model was employed to quantitatively study the effect of convection on pattern selection and growth rate of 2D and 3D dendrite tip,as well as the effect of the different convection velocity on the dendritic growth.The calculated results show that crystal is asymmetric in the priority direction of growth under flow.The dentritic growth is promoted in the upstream region and suppressed in the downstream region.Convection can cause deviation in the dendrite growth direction and the preferred direction of the columnar crystals.It has been found that both primary dendrite stem and secondary dendrite arm deflect significantly towards upstream direction,secondary dendrite arm in upstream direction is more developed than the primary dendrite in downstream direction.

Thermodynamic and kinetic study on interfacial reaction and diamond graphitization of Cu Fe-based diamond composite

Cu-Fe based diamond composites used for saw-blade segments are directly fabricated by vacuum and pressureassisted sintering. The carbide forming elements Cr and Ti are added to improve interfacial bonding between diamond and the Cu-Fe matrix. The interfacial reactions between diamond/graphite and Cr or Ti, and diamond graphitization are investigated by thermodynamics/kinetics analyses and experimental methods. The results show that interfacial reactions and graphitization of diamond can automatically proceed thermodynamically. The Cr3C2, Cr7C3, Cr23C6, and TiC are formed at the interfaces of composites by reactions between diamond and Cr or Ti; diamond graphitization does not occur because of the kinetic difficulty at 1093 K under the pressure of 13 MPa.

Crystallization kinetics of (Ni_(0.75)Fe_(0.25))_(78-x)Nb_xSi_(10)B_(12)(x=0,5) amorphous alloys

Amorphous ribbons of (Ni0.75Fe0.25)78-xNbxSi10B12（x=0,5） were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating,and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the (Ni0.75Fe0.25)78-xNbxSi10B12 amorphous alloy was annealed at the temperatures 715 and 745?K,a single phase of γ-（Fe,Ni） solid solution with grain sizes of about 10.3 and 18.5?nm,respectively,precipitates in the amorphous matrix. The crystallized phases are γ-（Fe,Ni） solid solution,Fe2Si,Ni2Si,and Fe3B after annealing at 765?K. The (Ni0.75Fe0.25)78-xNbxSi10B12 amorphous alloy was annealed at 720,750,and 800?K; and the crystallization phases,γ-（Fe,Ni） solid solution,（Fe,Ni） 23 B6,Ni 31 Si 12 and Nb2NiB 0.16 form simultaneously.

Crystallization kinetics of (Ni_(0.75)Fe_(0.25)_(78-x)Nb_xSi_(10)B_(12)(x=0,5)amorphous alloys

Amorphous ribbons of （Ni0.75Fe0.25）78-xNbxSi10B12 （x = 0, 5） were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating, and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the （Ni0.75Fe0.25）78Si10B12 amorphous alloy was annealed at the temperatures 715 and 745 K, a single phase of γ-（Fe, Ni） solid solution with grain sizes of about 10.3 and 18.5 nm, respectively, precipitates in the amorphous matrix. The crystallized phases are γ-（Fe, Ni） solid solution, Fe2Si, Ni2Si, and Fe3B after annealing at 765 K. The （Ni0.75Fe0.25）73NbsSi10 B12 amorphous alloy was annealed at 720, 750, and 800 K; and the crystallization phases, γ（Fe, Ni） solid solution, （Fe, Ni）23B6. Ni31Si12 and Nb2NiB0.16 form simultaneously.