Development of magnesium composite alloy by a new method combining B2O3 addition and melt stirring

For developing high performance magnesium alloys, a new method in combination of B2O3 addition and melt stirring was applied. When 0.3%, 6% and 12%（ mass fraction） B2O3 was added into pure Mg, many twins were produced in each alloy. The average grain size of Mg was about 200 μm. In Mg-6Al alloy, the grain size is decreased from 50 to 35 μm by B2O3 addition. In Mg-6RE （rare earth） alloys, the grain size is decreased from 35 to 15 μm. The grain size of Mg-9Al- 6Ti-3B2O3 alloy is about 5 μm. The hardness of pure Mg does not change by B2O3 addition. In Mg-6Al alloy, the hardness is increased by addition of 3% B2O3, however, the hardness of Mg-6RE alloy is decreased by B2O3 addition. Addition of B2O3 into Mg-Al, Mg-RE and Mg-Al-Ti alloys makes the fine grain structures, the hardness of Mg-RE alloy is decreased. This strange behavior may be interpreted with existence of many fine pores in the alloy. The mechanical properties of composite Mg-9Al-6Ti with 3?O3 are higher than those of AZ91C. The present results demonstrate the potential of this new method for developing high performance magnesium alloys.     

Grain size refinement of magnesium composite alloys by addition of B2O3

The high performance magnesium alloy was investigated by adding B2O3 in magnesium and magnesium alloys. Experiments include adding B2O3 in Mg, Mg-AI and Mg-RE alloys, respectively, studying the effects of B2O3 on the microstructure, were studied measuring the change of grain size and microhardness of the materials, discussing the change of grain size, morphology and distribution. The results show that adding 3% or 6%（mass fraction） B2O3 in Mg can bring twinning in Mg, adding B2O3 in Mg-Al alloys and Mg-RE alloys can refine the alloy grain size. Adding 3?O3 in Mg-6Al alloys can refine the average grain size by about 5 pro, with the average hardness increased by 13.3% （53.3-60.4 HV0.O3）; adding 6?O3 in Mg-6Al alloys can refine the average grain size by about 13 pro, with the average hardness increased by 15.8% （53.3-61.73 HV0.O3）; adding 3% and 6?O3 into Mg-6RE alloys can refine the grain size by about 5 and 9/am, respectively, with the average hardness decreased to HV0.03 64.66 and HV0.O3 57.86, respectively from HV0.03 88.57. In the Mg-6Al alloy the content of aluminum is increased, while in the Mg-6RE alloy the content of oxygen is decreased. It can be concluded that it is beneficial to develop Mg-Al-B-O particle reinforce composite alloys, and it is feasible to develop nanometer crystallization of block material by Mg-B-O-RE.