Papers by Author: Zhong Yang Cheng

Abstract: Laser cladding rapid manufacturing technology is a kind of new developed advanced manufacturing technology integrating the advantages of rapid prototyping manufacturing and laser cladding surface modification. Due to the complex thermo-physical and metallurgical factors in the deposition process, the cladding layer is liable to crack, which seriously impedes the industrial application of this technology. Experiments of laser cladding rapid manufacturing 316L stainless steel were carried out. The cracking behavior and phenomena has been observed, cracking mechanism of 316L stainless steel was investigated by means of microstructure characterization and phase analysis with optical microscopy (OM), X-Ray diffraction (XRD), scan electronic microscopy (SEM) and phase diagram analysis. Factors influencing the cracking susceptibility has also been studied. Results show that the cracks of 316L stainless steel were hot solidification cracks caused by the high residual stress and separating of the liquid films among dendrites. Through the optimization of process parameters, adding protective atmosphere, etc. cracking sensitivity has been effectively reduced and crack free 316L stainless steel components have been obtained.

Abstract: High performance biosensors are urgently needed from medical diagnosis, to food safety/security, to the war on bio-terrorist. Recently, magnetostrictive microcantilever (MSMC) and magnetostrictive particle (MSP) have been developed as high performance biosensor platform. Both MSMC and MSP are wireless sensors and exhibit advantages over current acoustic wave biosensor platforms. Theoretical analysis and experimental results indicate that micro/nano scale MSMC and MSP have ultra-high sensitivities. However, in real detection, there is a challenge faces all micro/nano scale sensors because of their small size. That is, a long time is required for the tiny sensors to react with the target species. Due to the magnetic and wireless nature, MSP provides a unique way to bring the nanosensors to target species. The fabrication of bar-like MSPs in nanoscale is reported. Amorphous Fe-B alloy was selected as target magnetostrictive materials for fabrication. The properties of these nanobars were determined. The morphology and magnetic properties of the nanobars were characterized. The results ware analyzed and the size effect on the microstructure and properties is discussed.