深过冷单相准晶块体材料的制备原理及技术研究

以获取厘米级单相准晶块体材料为目标,系统研究铝合金获得热力学深过冷的最佳净化方法途换?深过冷稳定准晶形成能力与成分,过冷度的关系,相数单一化稳定准晶形成规律,季宓纳ず托蚊蔡卣骷吧罟涠ㄏ蚰坦炭刂频募际豕丶?开发出深过冷单相准晶块体材料的制备技术,推动准晶物性和应用研究的开展..

A maximum undercooling, 180K was achieved in the Al72Ni12Co16 quasicrystal alloy melt by using the cyclic superheating technology and special crucible which has an ideal non-catalytic nucleation coating. The forming condition of single-phase decagonal quasicrystal was firstly studied. Besides, the microstructure evolution of Al72Ni12Co16 alloy with undercooling, the growth mechanism, the thermal stability and basic mechanical properties of decagonal quasicrystal were systematically investigated. The results indicate that the heterogeneous sites with witting angles smaller than 92o have been effectively deleted by the above melt purifyication technology. At small undercoolings, the decagonal quasicrystal preferred the lateral growth along the two-fold axis direction and formed the deca-prism microstructures in company with the formation of g-phase near the grain boundaries. When undercoolings were larger than the critical undercooling DTR, 65K, the growth mechanisms of decagonal quasicrystal varied from the step mode to continuous mode and the equiaxed microstructure of single-phase decagonal quasicrystal were formed. The single-phase decagonal quasicrystals formed in the undercooled melts have favourable stability at high temperature and no crystallization phenolmenon occurs. In addition, it found that the microhardness and brittleness of the single-phase decagonal quasicrystal are very high, while the fracture toughness of it is very low