Design And Implementation Of Monitoring System For Firefighters Combat

Magnesium alloy as the lightest structural material has become one of the most competitive emerging metal structure materials with a series of irreplaceable excellent performance.Thus,magnesium alloy has broad application prospects in the field of industrial production.With the wide application of magnesium alloy,the welding of magnesium alloy to other metals is inevitable;especially the welding of magnesium alloy to steel and magnesium alloy to aluminum alloy is paid more and more attention.There is no solid solubility and no mesophase formation between Mg and Fe elements.Therefore,the weldability is going to be faced for the joining of magnesium to steel.Although the physical properties between Mg and Al elements are closer,massive Mg-Al intermetallic compounds are generated in the joints.Hence,how to inhibit the formation of such brittle phases would be encountered for the joining of magnesium to aluminum.Contact reactive brazing is an effective method to realize the connection of dissimilar metals.Dissimilar metals joints with good performance can be obtained by selecting reasonable interlayers according to the different characteristics of matrix materials.In this paper,Zn-xAl as an interlayer are used in the joints of AZ31 magnesium alloy to DC01 galvanized steel and AZ31 magnesium alloy to 6061 aluminum alloy by contact reactive brazing.The effect of different interlayers' composition on microstructure and mechanical properties of joints was comparative analyzed.In-depth study on the formation process of the eutectoid particles and their strengthening and toughening mechanism for the joint was conducted.Research showed that A1 containing Zn-based interlayers can effectively avoid the emergence of ?1(Fe11Zn40)brittle phase in AZ31/DC01 joint.The fracture position of joint was Mg-Zn intermetallic compound region instead of Fe-Zn intermetallic compound layer.At the same time,it was found that using Zn-5A1 interlayer was conducive to strength enhancing of AZ31/DC01,AZ31/6061 joints by comparing Zn-xAl interlayers with different Al content,due to the composite structure of Al-based particulate phase dispersed between MgZn2 brittle phase grains,strengthening and toughening MgZn2 phase.The highest average shear strength of AZ31/DC01,AZ31/6061 joints was 79.1 MPa and 77.4Mpa.Through observation and analysis on microstructure of different interlayers and joints,it is found that part of the Al-based particulate phases in Zn-xAl interlayers with different Al content and AZ31/Zn-xAl/DC01,AZ31/Zn-xAl/6061 joints occurred eutectoid decomposition,generating nanoscale eutectoid particles which had enhanced capacity of plastic deformation.The eutectoid particles can refine MgZn2 grains,and block the crack propagation.The strengthening and toughening of joints was achieved through superplastic deformation of eutectoid particles and mechanical engagement in the interface between eutectoid particle and MgZn2 grain.