The Preparation And Application Of Nanosized (NbTi)C/Al Composite Powder By Mechanical Alloying

It is the main method to refine the solidification structure of aluminum alloy by means of intermediate alloy and second phase particles modification.TiC and NbC are considered to have a certain refining effect,but how to regulate the structure of carbides and make it uniformly dispersed in the liquid aluminum,still need further study.A new type of nano-(NbTi)C/Al composite powder was prepared by means of mechanical alloying in this paper.Regulate(NbTi)C structure and dispersity through adjusting the ratio between Nb and Ti and combining with Al,to refine the casting structure of aluminum alloy and improve the mechanical properties.On this basic,The refining capacity of the powder was evaluated,furthermore,the refining mechanism was investigated.Nano-(NbTi)C composite powder and(NbTi)C/Al composite powder was successfully prepared by mechanical alloying.Al powder was used as a carrier to cover the(NbTi)C particles,which can improve the agglomeration state and wettability of the carbides.At the same time,the addition of Al powder accelerated the synthesis of carbides,the size of(NbTi)C/Al composite powder prepared in this paper is about 100 nm.The(NbTi)C/Al composite powder was added to the liquid 1060 aluminum alloy with the purpose of evaluating the refinement effect of the powder.The results showed that the grain size of 1060 ingot was obviously reduced,and the area distribution of equiaxial crystal zone was increased.(NbTi)C/Al composite powder has a certain improvement effect on the mechanical properties of 1060,with a slight increase in hardness and tensile strength,as for the elongation rate,obvious improvement was not found.The refining effect of(NbTi)C/Al composite powder is inferior to that of commercial Al-Ti-B intermediate alloy.The reason is the loss of the powder caused by the burning and the low wettability of aluminum solution during the test.A conclusion can be drawn from the casting test of A356 aluminum alloy,the refining capacity of(NbTi)C/Al composite powder is already same as the Al-Ti-B intermediate alloy.The best refining effect can be get when the amount of Nb and Ti in the powder is same.the secondary dendrite size of α-Al is 31 um.During the tensile test,it was found that the elongation rate of the samples refined by(NbTi)C/Al composite powder was obviously increased compared to the samples refined by Al-Ti-B,but obvious improvement of the tensile strength is not found between the two kinds of sample.The sample with 0.15% Al-Ti-Nb-C remelting has the optimal elongation.The composite powder has recyclability,and the refining effect after remelting has not been declined.