Study On Heat-Treatment, Microstructure And Properties Of Al-Fe Alloy Plates

Al-Fe alloy as a new Heat-resistant aluminum alloys had pulled extensive attention, and developed rapidly since it was proposed. Rapid solidification or mechanical alloying technology can produce Heat-resistant aluminum-iron alloy of high strength. But the cost is high, technical and processes are complex, manufacturing deformation products are difficult. Therefore, using traditional techniques to produce Al-Fe alloy hot-rolled plates of high strength has very important practical significance.In this paper, the Al-Fe alloy plates were produced by solid-state extrusion, rolling processes. And using optical microscopy, X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) etc. testing methods, the microstruct-ures of Al-5%Fe-Based alloy at hot rolling, subsequent heat treatment and the strengthen-ing mechanism are systematically studied.The microstructure of Al-5%Fe-based alloy hot rolled plates is that the second phase particles of different sizes dispersing on the aluminiummatrix. The trend of larger second phase particles are the same as the rolling direction, with the distribution of chainlike, while many smaller second phase particles doping in the which. The grain elongates, stave along the direction of the force, then forms obvious distortion microstructures, moreover there are some degree of recrystallization and sub-grain structure in the matrix. Solution temperature and time have great influence on tensile properties of the Al-5%Fe-based alloy hot rolled plate. Increasing the temperature or extending the time of solution properly can accelerate the solution of excess phase, which can raise the degree of solution of alloy and improve the strength of alloy, but the excessive temperature or time of solution reduces the elongation of alloy. Along with the aging time extension, the strengthening phase precipitation gradually, aging time is short, strengthening phase precipitation is not adequate, the aging time is too long, strengthening phase particles grows so quick that alloy properties become worse. With the increasing of aging time,β-phase precipitates continuously at the grain boundary, absorbing the solute atoms of the space near it, forming a precipitate free zone, caused the alloy properties to reduce. The suitable single-stage heat treatment system as:solution temperature 565℃, solution time 80min, aging temperature 180℃, and aging time 6h, the tensile strength (Rm), yield strength (R) and elongation (A), respectively is 312MPa,300MPa and 3.8%. The fracture mode of the aged alloy is a mixed type with the intergranular and transgranular fracture. The intergranular fracture is mainly due to the hard particles of fracture center, the formation of PFZs and equilibrium phases along grain boundary.