Mechanical Properties And Damping Capacity Study Of Mg-Gd-Y-Al Alloys

In order to research a new kind of magnesium alloy with high strength anddamping capacity, which is used for mounting bracket of satellite instrument (made by2A14aluminum alloy now), four kinds of Al2RE/GWA alloys with different Gd/Ycompositions (GW111A:Mg-11.3Gd-1.2Y-1Al, GW151A:Mg-15.6Gd-1.2Y-1Al,GW181A:Mg-17.5Gd-1.1Y-1Al and GW133A:Mg-13.2Gd-2.9Y-1Al) were studied.The microstructures characteristics, mechanical properties and damping capacities ofthese Mg alloys were studied by heat treatment and hot extrusion.The vibrationperformances of four brackets were studied by sine excitation and impact method,which were made by different alloys(GW181A,GW103K,GW83K and2A14). Themain conclusions can be drawn as followings.The results indicate that the cast Mg-Gd-Y-Al alloys consist of-Mg, Al2(Gd, Y)and Mg24(Gd, Y)5phases. After solution treatment, strip-like LPSO compoundsappear at grain interiors, these compounds are parallel in one grain. The tensileproperties of as-cast Mg-Gd-Y-Al alloys have close relationships with the totalcontent of Rare Earth (RE) element. The higher total content of RE elementscorresponds to the higher strength and lower elongation. After solution treatment, theyield strength of the alloys drops a little, and the ultimate tensile strength increasesslightly, while the elongation improves obviously. After subsequent aging, the yieldstrength of the alloys increases significantly. The damping capacity of as-castMg-Gd-Y-Al alloys decreases with the increase of Gd addition, while the T6treatmentcan obviously increase the damping capacity of Mg-Gd-Y-Al alloy.For hot extruded alloys, higher yield strength and ultimate tensile strength can begot by increasing the content of RE addition with lower speed extrusion (1mm/s).After aging, the yield strength of GWA alloys all improves with an obvious drop onelongation. The damping capacity of extruded GWA alloys almost is all better thanthat of2A14alloy, only except GW151A alloy with extrusion speed1mm/s under450℃. In general, compared with as-cast alloy, magnesium alloy with high content ofrare earth is more likely to get higher yield strength and damping capacity bylow-speed extrusion. This is a way to obtain new magnesium alloys with high strengthand damping capacity.The damping performance of brackets could be assessed by the area of overallfrequence-response function curve (S) and inverse quality factor at the resonance peak(Q-1).In the same conditions, the smaller value of S or the larger value of Q-1indicates that the damping performance is better. For the unloaded brackets, the bracket madeby GW103K has the best overall damping performance, and for the brackets with load,the damping performance of bracket made by2A14is better than others, while thegap is small compared with Mg alloys. The damping capacity of GW181A alloy wasthe best in the earlier study, however after being manufactured into bracket, thedamping performance was bad than the bracket made by2A14. This result indicatesthat the actual vibration damping performance of bracket is not only related to thedamping capacity of materials, but also depends on other factors such as the shape andstructural stiffness.