(1. 湖南科技大学高功效轻合金构件成形技术及耐损伤性能评价湖南省工程研究中心，湘潭 411201；
2. 中南大学轻质高强结构材料国家级重点实验室，长沙 410083；
3. 湖南云箭集团有限公司，长沙 410100)
摘 要: 利用激光粉末沉积技术制备轻质Ti/Al密度梯度材料，采用扫描电子显微镜、电子探针显微分析仪、能谱仪、显微硬度测试仪等，分析了梯度材料的组织结构特征，研究了激光粉末沉积轻质Ti/Al密度梯度材料的裂纹形成机理及其自愈合行为。结果表明：轻质Ti/Al密度梯度材料的微观组织呈现渐变特征，相结构转变呈现Ti→Ti3Al→TiAl+Ti5Si3→TiAl3+TiAl+Ti5Si3+Al→Ti Al3+Al的规律变化；各梯度层(Ⅰ~Ⅴ)的平均硬度分别为370.9 HV0.1、619.4 HV0.1、567.7 HV0.1、459.5 HV0.1和213.8 HV0.1。梯度层中观察到裂缝存在，该裂纹在界面或缺陷(孔洞等)处萌生，在激光粉末沉积轻质Ti/Al密度梯度材料过程中，后续形成的熔池内金属溶液对裂纹具有填充作用，从结构上完成自修复，使裂缝得以愈合，可有效阻止裂纹进一步扩展。
关键字: 增材制造；激光粉末沉积；梯度材料；裂纹；自愈合行为；组织结构演变
（1. Hunan Engineering Research Center of Forming Technology and
Damage Resistance Evaluation for High Efficiency Light Alloy Components,Hunan
University of Science and Technology, Xiangtan 411201, China;
2. National Key Laboratory of Science and
Technology for High-strength Structural Materials,Central South University,
Changsha 410083, China;
3. Hunan Vanguard Group Co. Ltd., Changsha 410100,
China）
Abstract:A novel lightweight Ti/Al density gradient material was fabricated successfully using the laser powder deposition technology. The microstructures of gradient materials were characterized by the scanning electron microscope, electron probe microanalyzer, energy spectrometer and microhardness tester. The crack formation mechanism and self-healing behavior were studied. The results show that the microstructure of lightweight Ti/Al density gradient material shows gradual change, and the phase evolution shows the regular change of Ti→Ti3Al→TiAl+Ti5Si3→TiAl3+TiAl+Ti5Si3+Al→TiAl3+Al. The average hardness of each gradient layer (Ⅰ-Ⅴ) are 370.9 HV0.1, 619.4 HV0.1, 567.7 HV0.1, 459.5 HV0.1 and 213.8 HV0.1, respectively. The cracks are observed in the gradient layer, which initiate at the interface or defects (holes, etc.). In the process of laser powder deposition of light Ti/Al density gradient materials, the subsequent metal solution in the molten pool can fill the cracks, complete self repair structurally, make the cracks heal and effectively prevent the further expansion of cracks.
Key words: additive manufacturing; laser powder deposition; gradient material; crack; self-healing behavior; microstructure evolution
