The Effects Of Rapid Solidification And Heat Treatment On The Mechanical Propertie Of The Mg-Ni-Zn-Y Alloys

Mg based amorphous alloys are regarded as a new family of the promising structural materials for their high strength and low density. However, it is impossible to use such kind of materials because most of Mg-based BMGs exhibit no macro-plastic deformation under compression and the fracture toughness is comparable to the ideal brittle materials, such as SiO2. Therefore, how to improve the ductility of Mg-based BMGs has become a key issue in this area.In this paper, the microstructure, mechanical properties, etc of the Mg94-xNixY6 (x = 2,4,6,8) and Mg77+xNixZn5Y6 (x = 0, 2, 4, 6,8, 10, 12) series alloy are researched, and the formation and the relationship of the LPSO structures are preliminarily studied by TEM, and the affect of heat treatment on the microstructure, mechanical properties of Mg77+xNixZn5Y6 (x = 4,12) which have good comprehensive propertie also be studied. the following main conclusions are obtained:1) in Mg94-xNixY6 (x = 2,4,6,8) series of alloys, with the increase of Ni, the fracture strength are respectivelyεf = 422MPa, 568MPa, 622MPa and 773MPa, but the alloy plasticityσp = 12%, 20.6% , 15.3% and 8.9%.2) in Mg77+xNi12-xZn5Y6 (x = 0,2,4,6,8,10,12) series of alloys, Mg77Ni12Zn5Y6 and Mg81Ni8Zn5Y6 are amorphous matrix composite materials, and 14H-LPSO structure was found in the needle-likeα-Mg phase, with the Ni content increasing, amorphous phase increase, and the fracture strength of these alloys is up after the first down, while the plastic was first increased and then decreased, the 6H-LPSO structure is found in the Mg89Zn5Y6, while the alloy is mainly lamellar phase and only a very small amount of amorphous alloys .3) the alloy of Mg77+xNi12-xZn5Y6 (x = 4, 12) are heat treated at 200℃, results show for Mg89Zn5Y6 alloy after heat treatment, long-period phase structure has not changed, but the morphology and distribution has changed , resulting in the performance of the alloy changed, compressed plastic down after the first up, while the fracture strength has been increasing. For the Mg81Ni8Zn5Y6 alloy after heat treatment, amorphous phase is gradually crystallization, and the blackα-Mg phase gradually grow up. with the heat treatment time increased, the strength gradually decreased while the plastic began to rise, but the alloy strength and plasticity are significantly reduced at 16 hours.4) the alloy of Mg77+xNi12-xZn5Y6 (x = 4,12) are heat treated at 500℃. results shows for Mg89Zn5Y6 alloy, it reach a steady state after 1 hour's heat treatment, while the lamellar microstructure disintegration and white dots precipitate out, with the heat-treatment time increasing, less impact on the organization and performance. Strength of the allysσp = 600MPa or so,and plasticεf = 22% after heat treatment. For the Mg81Ni8Zn5Y6 alloy after heat treatment, amorphous phase and needle-like phase were disintegrated, and their mechanical properties deteriorated, but good performance at 10 hour's heat treatment,σp = 500MPa,εf =25%.