Effect of laser scanning speed on the microstructure, phase transformation and mechanical property of NiTi alloys fabricated by LPBF

Materials & Design

Lishan Cui¹  Yang Ren¹  Ying Yang²  Bo Feng³  Wenqian Guo³  Shijie Hao³  Qin Yang⁴  Hong Yang⁴  Yinong Liu⁵  Xin Tong⁶ 

[1] Corresponding authors.;College of Chemical Engineering and Environment, China University of Petroleum, Beijing 102249, China;College of New Energy and Materials, China University of Petroleum, Beijing 102249, China;Department of Mechanical Engineering, The University of Western Australia, Perth, WA 6009, Australia;Department of Physics, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong Special Administrative Region, China;Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang 621900, China;

关键词: Laser powder bed fusion;    NiTi shape memory alloy;    Laser scanning speed;    Martensitic transformation;    Residual stress;   

DOI  :  

来源: DOAJ

【 摘 要 】

This study investigated the effects of laser scanning speed on the microstructure, phase transformation and properties of NiTi alloys fabricated by laser powder bed fusion (LPBF). In this study, the contributions of metallurgical factors under different scanning speeds, such as Ni evaporation, Ni4Ti3 precipitation, dislocations and internal stress, to the transformation temperature and transformation latent heat were clarified through specially designed experiments. Ni evaporation is found to have the most profound effect, followed by precipitation. Increasing scanning speed is found to reduce Ni loss, thus cause less increase in the transformation temperature and transformation heat of the LPBF-NiTi alloys. Increasing scanning speed also increases the microstructure non-uniformity and thus widens the transformation temperature interval. The orientations of residual stress exhibit strong crystallographic stiffness dependence. The LPBF-NiTi alloys with different scanning speeds all exhibited high strains (>13.4%) and excellent shape memory effect. A LPBF-NiTi honeycomb structure exhibited 96% shape recovery rate after a 60% pre-compressive deformation. Besides, there is an optimum scanning speed for minimum porosity and smallest average pore size. However, the pore structure is found to have weak influence on the tensile behaviour of the LPBF-NiTi alloys, possibly due to the high defect tolerance of the martensitic transformation.

【 授权许可】

Unknown