Yongyun Zhang

Study on the Phase Modulation Characteristics of Liquid Crystal Spatial Light Modulator

A special Twyman-Green interferometer is designed to measure the phase modulation characteristics of liquid crystal spatial light modulator (LC-SLM), namely, the relationship between phase shift and gray value (applied voltage). By measuring a reflective LC-SLM produced by BNS (Boulder Nonlinear Systems), it is indicated that the LC-SLM has linear phase response within a gray value range between 60 and 200, and the RMS deviation between the average phase and the spatially resolved phase measurements increases with the gray value but is always less than λ/10.

Formation of intermetallic compound layer in multi-laminated Ni–(TiB2/Al) composite sheets during annealing treatment

Solid-state reactive diffusion between Ni and Al was investigated during annealing at 650°C by employing multi-laminated Ni-(TiB(2)/Al) composite sheets. In multi-laminated Ni-(TiB(2)/Al) composite sheets annealed up to 5min NiAl(3) was the only phase observed in the diffusion zone, and Ni(2)Al(3) appeared after longer annealing time. Most grains of Ni(2)Al(3) showed equiaxed morphology rather than columnar microstructures like NiAl(3), due to the low concentration gradients of Al and Ni at the Ni/NiAl(3) interface. The preferential formation of this intermetallic compound NiAl(3) in multi-laminated Ni-(TiB(2)/Al) composite sheets was predicted using an effective heat of formation model. The present work indicated that both Ni and Al interdiffused, and the formation of NiAl(3) was a reaction-diffusion process.

Superplasitic Tensile Behavior of in Situ TiBw/Ti6Al4V Composite with Novel Network Microstructure

In situ TiB whiskers reinforced Ti6Al4V (TiBw/Ti64) composites with a novel network microstructure were successfully fabricated by reaction hot pressing. The novel composites exhibited a superior combination of mechanical properties at room temperature and a superior strengthening effect at 400–600°C. In the present work, superplastic tensile behavior of the novel composite was carried out at 900–1000°C. The tensile elongation of the novel composite is always over 100% when the tensile temperature is over 900°C. The elongation of the composite firstly increases and then decreases with increasing tensile temperatures. In particular, the tensile elongation is up to 214% at 940°C, which can be viewed as the highest ductility for the as-sintered discontinuously reinforced titanium matrix composites (DRTMCs) fabricated by powder metallurgy (PM) process up to date. The superior ductility can be attributed to the novel network microstructure including the TiBw-lean region and the TiBw-rich network region.