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In view of the large difference between the elastic modulus of human bone structure and metal materials and the difficulty of control, the goal is to reduce or eliminate the “stress shielding” effect in a wide span, introduce a negative Poisson’s ratio metamaterial with an unconventional deformation mechanism, carry out the design and experimental research of porous microstructure with wide span and low elastic modulus. Based on the negative Poisson’s ratio auxetic structure unit, the three-dimensional cellular porous microstructures with different control parameters and porosity were designed.Experimental samples were prepared by selective laser melting. The variation rules between mechanical properties and structural parameters such as strength and elastic modulus were revealed through compression tests, and the matching degree of negative Poisson’s ratio microstructure and human bone was evaluated. The experimental results show that the auxetic structure has good manufacturability, and the forming quality is correlated with the concave angle and porosity.The mechanical properties of negative Poisson’s ratio auxetic structure are highly dependent on the geometric structure and porosity of the cell.Compared with the positive Poisson’s ratio structure, the auxetic structure with negative Poisson’s ratio has lower elastic modulus and similar yield strength under the same porosity, and can control the 316 L stainless steel bone material with wide span elastic modulus by 0.47 GPa～1.75 GPa.Therefore, the negative Poisson’s ratio auxetic microstructure has potential advantages in the application of human bone structure.

Gradient Ti6Al4V porous scaffolds were designed based on triply periodic minimal surfaces (TPMS) and were fabricated by SLM technology. The effects of edge porosity Pout, center porosity Pin and average porosity P on mechanics properties and energy absorption were analyzed. The results show that elastic modulus, compressive strength and total absorbed energy per unit volume VV of gradient porous scaffolds with the same P all decrease with the increase of Pout and increase with the increase of Pin. The elastic modulus, compressive strength and Wv of gradient porous scaffolds with the different P all decrease with the increase of P. P has greater influence on elastic modulus, compressive strength and Wv than Pin and Pout. The printed gradient porous scaffolds meet the requirements of elastic modulus and compressive strength of femur and tibia. The mechanics property model established may provide a reference for the applications of porous scaffolds in orthopedics. [ABSTRACT FROM AUTHOR]

The purpose of this investigation is to test the laser cladding of different alloy powders onto 1045 medium-carbon steel substrates for parts remanufacturing. The types of alloy powder, laser output powers, and scanning speeds are selected as influencing factors to conduct laser cladding experiments with orthogonal design on the carbon steel 1045 substrate. Bonding shear strength and microhardness of the cladding layer and the substrate are tested and analyzed. The high resolution scanning electron microscopy and energy dispersive X-ray spectroscopy are also used to analyze cladding layers, microstructures, and elements. The experimental results show that a good metallurgical bond is formed between the cladding layer and the substrate without porous cracks and other defects. Shear stress intensity of nickel-based powder is two to three times higher than that of substrate material, while iron-based powder is five times higher than the substrate material. The type of the powder is the most significant factor and laser power is the least. The hardness of outer cladding layer is higher than that of bonding section and inner section. In the heat-affected zone, hardness is higher than that of the substrate material. [ABSTRACT FROM AUTHOR]