Grain size refinement of magnesium composite alloys by addition of B2O3
(3.Graduate School of Science and Technology，Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan
4.Department of materials Science and Engineering, Faculty of Engineering, Kumamoyo University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan)
4.Department of materials Science and Engineering, Faculty of Engineering, Kumamoyo University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan)
Abstract: The high performance magnesium alloy was investigated by adding B2O3 in magnesium and magnesium alloys. Experiments include adding B2O3 in Mg, Mg-Al 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%B2O3 in Mg-6Al alloys can refine the average grain size by about 5 μm, with the average hardness increased by 13.3% (53.3？60.4 HV0.03); adding 6%B2O3 in Mg-6Al alloys can refine the average grain size by about 13 μm, with the average hardness increased by 15.8% (53.3？61.73 HV0.03); adding 3% and 6%B2O3 into Mg-6RE alloys can refine the grain size by about 5 and 9 μm, respectively, with the average hardness decreased to HV0.03 64.66 and HV0.03 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.
Key words: magnesium alloys; grain size refinement; composite alloys; B2O3; particle reinforce; compo-casting