Microstructural evolution of Al-20Si-5Fe alloy during rapid solidification and hot consolidation

• Published in: Rare metals 2009-12, Vol.28 (6), p.639-645
• Main Authors: Rajabi, M., Vahidi, M., Simchi, A., Davami, P.
• Format: Article
• Language: English
• Subjects: Alloys; Biomaterials; Chemistry and Materials Science; Consolidation; Cooling; Energy; Materials Engineering; Materials Science; Metallic Materials; Metallurgy; Nanoscale Science and Technology; Physical Chemistry; 二次枝晶臂间距; 冷却速度; 凝固过程; 微观力学性能; 微观组织演变; 金属间化合物
• ISSN: 1001-0521; 1867-7185
• DOI: 10.1007/s12598-009-0122-3

Al-20Si-5Fe melt was rapidly solidified into particles and ribbons and then consolidated to near full density by hot pressing at 400℃/250 MPa/1 h. According to the eutectic-growth and dendritic-growth velocity models, the solidification front velocity and the amount of undercooling were estimated for the particles with different sizes. Values of 0.43-1.2 cm/s and 15-28 K were obtained. The secondary dendrite arm spacing revealed a cooling rate of 6 × 10^5 K/s for the particles with an average size of 20 μm. Solidification models for the ribbons yielded a cooling rate of 5 × 10^7 K/s. As a result of the higher cooling rate, the melt-spun ribbons exhibited considerable microstructural refinement and modification. The size of the primary silicon decreased from approximately 1μm to 30 nm while the formation of iron-containing intermetallic compounds was suppressed. Supersaturation of the aluminum matrix in an amount of-7 at.% Si was noticed from the XRD patterns During the hot consolidation process, coarsening of the primary silicon particles and precipitation of β-Al5FeSi phase were observed. Evaluation of the compressive strength and hardness of the alloy indicated an improvement in mechanical properties due to the microstructural modification.