电场对Al-Mn-Mg合金的微结构和织构形成的影响

利用透射电子显微镜观察(TEM)和X射线衍射技术(ODFs分析),研究了电场对Al-Mn-Mg合金的回复和再结晶组织演变、再结晶织构的形成和发展的影响.结果表明,电场对再结晶的影响其强度有一个门槛值(3～4 kV/cm),低于此值电场对该合金的再结晶没有明显的影响.强度为4 kV/cm的电场对再结晶形核的影响较大,可抑制Al-Mn-Mg合金的回复和再结晶,促进再结晶立方织构的形成.其主要原因是电场降低了各取向的形变储能,推迟了再结晶进程,抑制储存能小的取向晶核的形成和长大,促进储存能大的S取向晶粒向立方织构择优生长.     

Microstructure and texture analysis of YBCO thick film with peritectic growth on unoriented silver substrate

YBCO textured thick film was prepared by direct periteetic growth method. Microstructure of the film was characterized. Electron backscattered diffraction (EBSD) technique was applied to the film for quantitative texture analysis. The main difficulty in resolving the ori-entation of YBCO pseudo-cubic structure was investigated. Automated orientation mapping was performed on YBCO thick film. Local tex-ture was presented in the form of orientation maps. Misorientation distribution and crystal growth characterization in the YBCO thick film were revealed. Large domains with well-aligned YBCO grains were formed. Each domain presented clear in-plane and out-plane textures.     

Deformed texture of copper processed by equal channel angular pressing via different angle routes

The commercially pure copper with dimension of 80 mm×20 mm×4 mm was used for equal channel angular pressing （ECAP）, of which their outward appearance coordinate is corresponded with that of rolling deformation modes. Cold-deformed texture was investigated. The results show that the texture character in pure copper processed by ECAP is related with intersection angle （Ф） of the die channel. When Ф is 90° and the sample is extruded for one pass, its texture consists of α and β orientation lines including mainly C, B, S and Goss components, moreover a little rotated cube is found. When Ф is 135°, as extrusion pass increases, the weak texture forms on the scope of deviation from rotated cube （ψ=0°, θ=0°, Ф=45°＋15°） and develops to the ψ=45° fiber mainly including rotated cube. When Ф is 120°, the texture is ψ=45° fiber mainly including rotated cube that is maintained constant as extrusion pass increases.     

Microstructural Tailoring During Solid-State Transformation by EPM

Ni-Mn-Ga ferromagnetic shape memory alloys can generate large output with fast dynamic response at the application of the magnetic field and is considered as a new class of functional materials.Since the martensite of these alloys is highly magnetocrystalline anisotropic,introducing a magnetic field during their martensitic transformation could be an effective way to control variant distribution and realize texturation.In this work,some of our recent results achieved in microstructural and crystallographic texture modification by EPM(Electromagnetic Processing of Materials)during solid-state phase transformations of Ni-Mn-Ga alloys were summarized.Moreover,the entropy change induced by magnetic field in Ni-Mn-Ga melt-spun ribbons were also presented.     

Effects of electric field on recrystallization texture evolution in cold-rolled high-purity aluminum sheet during annealing

The effects of an external DC(direct current)electric field on recrystallization texture evolution in the cold-rolled aluminum sheets with 99.99%purity were investigated by means of X-ray diffraction techniques.The cold-rolled high-purity aluminum sheets were annealed for 60 min at 200,300 and 400℃,respectively with and without an external DC electric field of 800 V/mm.The results show that with DC electric field,the recrystallization cube texture is strengthened at the stage of grain growth. Possible reason for the strengthening of the recrystallization cube texture with the applied electric field may be attributed to both selected nucleation and selected growth of cube oriented crystal nuclei.     

Texture Evolutions in Fe-6.5% Si Produced by Rapid Solidification and Chemical Vapor Deposition

Fe-Si ribbons and thin sheets with 6.5%Si content were prepared by means of the single roller rapid solidification and chemical vapor deposition (CVD), respectively. The initial textures of rapidly solidified Fe-6.5%Si ribbons were characteristic of the {100} fiber-type, which became weakened during primary recrystallization in various atmospheres. At the stage of secondary recrystallization, the {100} texture formed in Ar and the {110} texture in hydrogen, while there occurred a texture transformation from the {100} type to the {110} type in vacuum with the increase of annealing temperature. For Fe-6.5%Si sheets prepared by Si deposition in cold-rolled Fe-3%Si matrix sheets, their textures were dominated by the η-fiber (<001>//RD) with the maximum density at the {120}<001> orientations. After homogenization annealing, the η-fiber could evolve into the {130}<001> type or become more concentrated on the {120}<001> orientations, depending on the cold rolling modes of Fe-3%Si matrix sheets.