Full
Outline
NiTi alloy has garnered significant attention due to its unique functional properties， and laser powder bed fusion has become the mainstream additive manufacturing technique for producing NiTi alloy components. However， the surface roughness of as-fabricated parts is generally too high to permit direct assembly and application， and it is difficult to reduce via conventional machining. Laser remelting， as a non-contact surface treatment technique， can modify the surface morphology and microstructure of materials. This work aims to reduce the surface roughness of NiTi alloy fabricated by laser powder bed fusion through laser remelting， and to elucidate its effects on the mechanical and functional properties of the alloy. Based on experimental data， a regression equation relating the laser remelting process parameters to surface roughness is established. The optimal parameter combination is determined through response surface optimization. The differences in mechanical properties and superelasticity of the alloy before and after laser remelting are evaluated， and the underlying mechanisms are analyzed via microstructure characterization. The results show that the optimal parameter combination for laser remelting is a defocusing distance of 175 mm， a spot diameter of 0.1 mm， a pulse frequency of 250 MHz， a laser power of 60.2 W， and a scanning speed of 1966.4 mm/s. After remelting， the roughness of the alloy decreases from 8.04 μm to 0.763 μm， the tensile strength increases from 588 MPa to 656 MPa， and the stable recoverable strain in tensile superelasticity improves from 2.1% to 2.8%. The enhancement in strength can be primarily attributed to grain refinement in the remelted surface layer， while the improved superelastic stability and recoverable strain result from the synergistic effects of grain refinement and the precipitation of Ti2Ni phase.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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