Effect of temperature on solid-state formation of bulk nanograined intermetallic Al3Ni during high-pressure torsion
Effect of temperature on solid-state formation of bulk nanograined intermetallic Al3Ni during high-pressure torsion
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DOI：
10.1080/14786435.2013.868945
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发表时间：
2014-03-24
影响因子：
1.6
通讯作者：
Horita, Zenji
中科院分区：
文献类型：
--
作者：
Alhamidi, Ali;Edalati, Kaveh;Horita, Zenji
采用高压扭转（HPT）方法，通过剧烈塑性变形制备了块状纳米晶金属间化合物Al 3 Ni。在6 GPa的压力下，在室温（RT）至573 K的范围内的选定温度下，通过HPT处理75mol%Al和25mol%Ni的粉末混合物。X射线衍射分析显示，在室温下加工50转后形成了Al 3 Ni金属间化合物，但随着加工温度的升高，形成Al 3 Ni所需的转数更少（即施加的应变更低）。通过透射电子显微镜观察表明，在3和10转后，显微结构由尺寸为300-2000 nm的超细晶粒组成。一旦在较高转数后形成Al 3 Ni，尺寸为~30 nm的等轴纳米晶粒占优势，硬度显著增加。硬度的增加是更显着的，当在较高的温度下处理，因为增加的分数的Al 3 Ni。结果表明，固态形成的Al 3 Ni发生由于通过存在高密度的晶格缺陷，增强扩散（即降低扩散活化能）。
A bulk form of nanograined intermetallic Al3Ni was produced by severe plastic deformation using high-pressure torsion (HPT). Powder mixtures of 75 mol% Al and 25 mol% Ni were processed by HPT at a selected temperature in the range of room temperature (RT) to 573 K under a pressure of 6 GPa. X-ray diffraction analysis revealed that the Al3Ni intermetallic formed after processing for 50 revolutions at RT but, as the processing temperature increased, less revolutions (i.e. lower imposed strain) were required for the formation of Al3Ni. Observations by transmission electron microscopy showed that the microstructure consists of ultrafine grains having a size of 300-2000 nm after 3 and 10 revolutions. Once the Al3Ni formed after a higher number of revolutions, equiaxed nanograins with a size of ~30 nm prevailed with a significant increase in hardness. The increase in hardness was more significant when processed at higher temperatures because of increasing the fraction of Al3Ni. It was shown that the solid-state formation of Al3Ni occurred due to enhanced diffusion (i.e. decreased activation energy for diffusion) through the presence of high density of lattice defects.