Surface Substructure and Properties of ZrB2p/6061Al Composite Treated by Laser Surface Melting under Extreme Cooling Conditions

High Temperature Materials and Processes

卷:36

Guo Weijia¹  Cai Yangchuan¹  Lu Tong¹  Chao Yuhjin¹  Deng Lingzhu¹  Lei Yuchen¹  Luo Zhen¹  Zeng Yida¹  Wang Zihao¹  Huang Yongxian² 

[1] School of Material Science and Engineering, Tianjin University, Tianjin 300072, China;

[2] State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China;

关键词: laser melting;    zrb2p/6061al composite;    finer distribution;    thermal mismatch stress;   

DOI  :  10.1515/htmp-2015-0069

来源: DOAJ

【 摘 要 】

Particulate reinforcement composite ZrB2p/6061Al was fabricated from Al-K2ZrF6-KBF4 by a direct melt reaction. Laser surface melting was used to improve the surface strength of the in situ ZrB2p/6061Al composite, which includes a series of laser-melted composites with different laser power and cooling conditions processed by a 2-kW yttrium aluminum garnet laser generator. The surface substructure of these laser-treated specimens was investigated by light optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffractometry and transmission electron microscopy. The penetration depth of the molten pool increases with increases in power density, and decreases with increases in the degree of undercooling. The Vickers hardness of the laser-melted composites reached 60–75.2 HV in liquid nitrogen and 56–64.0 HV in air, and increased by 50.4 % and 28 %. Grain refinement with decreased cellular spacing is important in strength performance. Because of a thermocapillary flow vortex and α-Al phase precipitation, nano-ZrB2 particles were distributed along the cellular dendrite boundary as observed by scanning electron microscopy. This was considered to be a key factor responsible for the improved mechanical composite properties. When cooling under liquid nitrogen, the thermal mismatch stress between particles and the matrix generates a high dislocation density. The dislocation grows along the interface between the matrix and particles and provides the laser-melted composites with additional strength.

【 授权许可】

Unknown