Effect of Sn on synthesis of nanocrystalline Ti-based alloy with fcc structure

Sn对制备具有纳米晶fcc结构钛基合金的影响

The effect of the amount of Sn on the formation of fcc phase in Ti-13 Ta-x Sn(x=3,6,9 and 12,at.%)alloys was studied.The alloys were synthesized by mechanical alloying using a planetary mill,jar and balls of stabilized yttrium.Using Rietveld refinement,it was found that the obtained fcc phase has crystallite size smaller than 10 nm and microstrain larger than 10-3.Both conditions are required to form an fcc phase in Ti-based alloys.For all samples,the microstructure of the fcc phase consists of equiaxial crystallites with sizes smaller than 10 nm.The largest presence of fcc phase in the studied Ti alloy was found with 6 at.%Sn,because this alloy exhibits the largest microstrain(1.5×10-2)and crystallite size of 6.5 nm.Experimental data reveal that a solid solution and an amorphous phase were formed during milling.The necessary conditions to promote the formation of solid solution and amorphous phases were determined using thermodynamic calculations.When the amount of Sn increases,the energy required to form an amorphous phase varies from approximately 10 to approximately-5 k J/mol for 3 and 12 at.%Sn,respectively.The thermodynamic calculations are in agreement with XRD patterns analysis and HRTEM results.

研究Sn含量对Ti-13Ta-xSn(x=3,6,9,12,摩尔分数,%)合金中fcc相形成的影响。合金采用机械合金化方法制备,所用设备为行星式球磨机。通过Rietveld分析发现,fcc相的晶粒尺寸小于10 nm,微应变大于10-3,这两个条件是钛基合金中形成fcc相所必需的。对于所有的样品,fcc相的显微组织中均含有小于10 nm的等轴晶。当Sn含量为6%时,钛合金中fcc相的含量最大,因为该合金具有最大的微应变(1.5×10-2)和晶粒尺寸(6.5 nm)。实验数据表明,球磨过程中形成固溶体和非晶相。用扩展Miedema模型对促进固溶体和非晶相形成的必要条件进行热力学计算。结果表明,当Sn含量从3%增加到12%时,形成非晶相所需的能量从大约10 k J/mol变为-5 k J/mol左右。热力学计算结果与XRD分析和HRTEM结果一致。