Study On Ageing Characteristics Of Mg₂B₂O_5W/ZK60 Magnesium Matrix Composites

Magnesium Alloys poor mechanical properties,corrosion resistance of poor and poor high-temperature creep make its application limited.Compared with magnesium alloy,magnesium matrix composites have the strength and mechanical properties such as modulus significantly increased,high temperature creep performance has improved, but maintained the stability of the size of magnesium,and the advantages of high damping,get more extensive attention and study.Powder Metallurgy(PM)is an approach to prepare at certain temperature.In this paper,ZK60 alloy were chosen as the matrix alloys,the boric acid magnesium whisker(the boric acid magnesium whisker(Mg₂B₂O_5W)as a new material with similar mechanical properties of carbon fiber,while its price is the 1/20～1/30 polycrystalline silicon carbide,because of its high performance and low price in the tremendous applications in the civilian material prospects,so it becomes the focus of research in the area of materials)was used as the reinforcement,15%(vol)Mg₂B₂O_5W/ZK60 magnesium matrix composites was prepared by powder metallurgy.The microstructure of Mg₂B₂O_5W/ZK60 magnesium matrix composites was observed by means of metallographic microscope(OM), scanning electron microscopy(SEM)and transmission electron microscopy(TEM). The phase composition of Mg₂B₂O_5W/ZK60 magnesium matrix composites was studied by means of X-ray diffraction(XRD)and Energy Dispersive X-ray Spectroscopy(EDS).The mechanism of Mg₂B₂O_5W/ZK60 magnesium matrix composites and the age behavior of ZK60 matrix alloy were studied.The micro-hardness of Mg₂B₂O_5W/ZK60 magnesium matrix composites rise to 30%than the micro-hardness of ZK60 matrix alloy,The micrographs reveal reasonably uniform distribution and random orientation of Mg₂B₂O_5Wthe as Mg₂B₂O_5W/ZK60 magnesium matrix composites fabricated by powder metallurgy, and without pores defect in the composite.After the solid solution aging treatment, the interfacial phenomena in Mg₂B₂O_5W/ZK60 magnesium matrix composites are systematically investigate by using TEM.The investigation shows that there are not interfacial reaction products at Mg₂B₂O_5W/ZK60 magnesium matrix composites interface.The solid solution treatment(400℃for 8h)made the micro-hardness of Mg₂B₂O_5W/ZK60 magnesium composites decrease to 24%,When the solid solution for more than eight hours after the hardness up.The solid solution(400℃for 8h) aging(170℃for 20h)treatment could make the micro-hardness of ZK60 matrix alloy rise to 19%,the solid solution(400℃for 8h)aging(170℃for 14h)treatment could make the micro-hardness of Mg₂B₂O_5W/ZK60 magnesium matrix composites rise to 16%.The results show that the peak-solution time at 400℃is 8h,and the peak-aging time at 170℃is 14h to Mg₂B₂O_5W/ZK60 magnesium matrix composites.The aging hardness of Mg₂B₂O_5W/ZK60 magnesium matrix composites has always been higher than that of the corresponding ZK60 matrix alloy.So Mg₂B₂O_5W obviously reinforced magnesium alloy.The introduction of Mg₂B₂O_5Whas not changed the general rules of age-hardening of magnesium alloy.There are two peaks on the aging hardness curves of composite materials and matrix alloy.The introduction of Mg₂B₂O_5Wimproved the aging speed.Corresponding,on the aging hardness curves,two hardness peak time of Mg₂B₂O_5W/ZK60 magnesium matrix composites significantly advanced than that of matrix alloy.