高能球磨制备Mg_xTi_(100-x)合金的微观组织及储氢性能

Microstructure and hydrogen storage performance of alloys Mg_xTi_(100-x) prepared by high-energy ball milling

应用振动高能球磨机械合金化方法制备MgxTi100-x(x=35,50,65,80)系列合金,采用XRD、SEM、TEM以及吸放氢测试等手段分析研究Mg含量与球磨时间对MgxTi100-x球磨产物微观组织演化规律、相结构和吸氢行为的影响.结果表明:在相同球磨时间(20h)下,球磨合金MgxTi100-x微观组织的相组成与Mg含量关系密切,当Mg的质量分数按35%～80%依次增加时,其球磨产物的相组成依次为BCC型、FCC型、FCC型(主相)+BCC型+HCP型和HCP型(主相)+FCC型,其中各物相的晶胞参数随Mg含量的增加而减小.随球磨时间的增加,Mg35Ti65球磨产物的微观组织发生显著变化,当球磨时间较短时(t=1～15h),易先形成少量的FCC型固溶体相,当球磨时间t≥20h后则形成单一的BCC型固溶体相.具有BCC型结构的Mg35Ti65球磨合金在8MPa氢压和200℃时其最大储氢质量分数达到3.8%,并表现出较好的吸氢动力学特性,而具有FCC型或HCP型(主相)+FCC型混合相的球磨合金MgxTi100-x(x=50,65,80),其吸氢容量比较小.

A series alloys MgxTi100-x（x=35,50,65,80） were prepared by using mechanical alloying method with vibratory high-energy ball-milling.The effect of Mg content and milling time on the microstructural evolution,phase structure and hydrogen storage performance were analyzed and investigated by XRD,SEM,TEM and hydrogen absorption/discharging test.The experimental results showed that the microstructure of the alloys MgxTi100-x was closely related to the Mg content under the condition of identical milling time.With increasing Mg content successively from 35 to 80,the phase constitution of the alloys would successively be of BCC type,FCC type,FCC type（principal phase） ＋ BCC type ＋ HCP type and HCP type ＋ FCC type,in which the crystal parameters would decrease with the content of Mg.For the alloy Mg35Ti65,the change in its microstructure with milling time was remarkable.When milling time was 1～15 h,a small amount of FCC-type phase would be formed,and almost single BCC type phase would be finally obtained when milling time was 20 h. The alloy Mg35Ti65 with BCC type structure could release about 3.8% of hydrogen and exhibited good hydrogen storage kinetics at 200 ℃ and 8 MPa.The alloys MgxTi100-x（x=50,65,80）with FCC type or HCP type ＋ FCC type structure,however,absorbed only less amount of hydrogen.