Preparation Of TiC/Al And NbC/Al Composite Powders And Effects On Grain Refinement For 1060 Aluminum Alloys

The refinement of aluminum alloys is always a hot topic in aluminum alloy research.The modification has became the main method of refining the as-cast structure of aluminum alloys.Recent years,people have attempted to add ultrafine ceramic particles in liquid aluminum to refine grain,however,the poor wettability between inter-particle and the liquid aluminum reduces the refinement.Therefore,how to improve the wettability between liquid aluminum and inter-particle is the key to the refining agent widely used.In this thesis,TiC and NbC particles were prepared by high-energy ball milling.TiC and NbC were wrapped by Al,and the TiC/Al and NbC/Al particles were obtained.The aim was to improve the wettability of the TiC and NbC particles.Furthermore,the effects of TiC/Al and NbC/Al on the as-cast structure of 1060 were investigated,and the influence of the smelting temperature on the grain refinement was also considered.The milled TiC and NbC can be prepared using Ti,Nb and graphite powders by mechanical alloy,respectively.Adding Al can accelerate the synthesis of TiC,and Al can be dissolved into TiC particles.The largest amount of solid solution is about 10%.Al has less effect on the synthesis of NbC,but it can significantly refine NbC particles.The size of NbC is reduced by about 60%.Adding Al to the TiC and NbC can get TiC/Al and NbC/Al composite particles,Al can reduce the carbide agglomeration phenomenon,and the stability of these powder is good.Adding TiC/Al or NbC/Al powder to smelting process,it can be uniformly dispersed in molten aluminum and refine the cast structure of pure aluminum.The grain size will be decreased with the increasing of the amount of added powder.TiC/Al has a better refinement effect than NbC/Al.When adding 5 wt.% TiC/Al,the grain size is about 1/5 of the original pure aluminium grain.The hardness can be obviously improved by adding TiC/Al or NbC/Al powder,however,the powder has a bad effect on the strength and the toughness,the reason for this needs to further study.The melting temperature has an effect on the refining effect,and the refining effect decreases with the increase of melting temperature.