Role of tensile forces in hot tearing formation of cast Al-Si alloy
(1. Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education),
Shandong University, Ji’nan 250061, China;
2. Jinan Foundry and Metalforming Machinery Research Institute Co., Ltd., Ji’nan 250022, China;
3. Shandong Shouguang Juneng Special Steel Co., Ltd., Weifang 262711, China)
Shandong University, Ji’nan 250061, China;
2. Jinan Foundry and Metalforming Machinery Research Institute Co., Ltd., Ji’nan 250022, China;
3. Shandong Shouguang Juneng Special Steel Co., Ltd., Weifang 262711, China)
Abstract: The instrumented applied rod casting apparatus (ARCA) was developed to investigate the effects of tensile forces in the hot tearing formation of cast Al-Si alloys. The obtained data of tensile forces/temperature was used to identify hot tearing initiation and propagation and the fracture surface of samples was also investigated. The result shows that the applied tensile forces have a complex effect on load onset for the hot tearing initiation and propagation. During the casting solidification, the tensile forces are gradually increased with the increase of solid fraction. Under the action of tensile forces, there will appear hot tearing and crack propagation on the surface of the sample. When the tensile forces exceed the inherent strength of alloys, there will be fractures on the sample. As for the A356 alloy, the critical fracture stress is about 0.1 MPa. The hot tearing surface morphology shows that the remaining intergranular bridge and liquid films are thick enough to allow the formation of dendrite-tip bumps on the fracture surface.
Key words: hot tearing; tensile force; A356 alloy; aluminum alloy; liquid film; solid fraction