Iwaszko Józef, Kudła Krzysztof
Department of Materials Engineering, Faculty of Production Engineering and Materials Technology, Czestochowa University of Technology, 19 Armii Krajowej Ave., 42-200 Czestochowa, Poland.
Department of Technology and Automation, Faculty of Mechanical Engineering and Computer Science, Czestochowa University of Technology, 21 Armii Krajowej Ave., 42-200 Czestochowa, Poland.
Materials (Basel). 2022 Apr 2;15(7):2633. doi: 10.3390/ma15072633.
A rolled plate of 7075 aluminum alloy was friction-stir-processed (FSP) with simultaneous cooling by an air stream cooled to -11 °C with a jet cooling nozzle. Two variants of air blowing were used: at an angle of 45° to the sample surface and at an angle of 90°. The reference material was a sample subjected to analogous treatment but naturally cooled in still air. The microstructural tests revealed strong grain refinement in all the samples, with higher grain refinement obtained in the air-cooled friction-stir-processed samples. For the naturally cooled samples, the average grain size in the near-surface area was 7.6 µm, while for the air-cooled sample, it was 1.4 µm for the 45° airflow variant and 3.2 µm for the 90° airflow variant. A consequence of the greater grain refinement was that the hardness of the air-cooled friction-stir-processed samples was higher than that of the naturally cooled samples. The improvement in abrasive wear resistance was achieved only in the case of the friction-stir-processed specimens with air cooling. It was found that the change in the air blowing angle affects not only the degree of grain refinement in the stirring zone, but also the geometrical structure of the surface. In all the samples, FSP caused redistribution of the intermetallic precipitates combined with their partial dissolution in the matrix.
对一块7075铝合金轧制板材进行搅拌摩擦加工（FSP），同时通过喷射冷却喷嘴用冷却至-11°C的气流进行冷却。使用了两种吹气方式：与样品表面成45°角吹气和与样品表面成90°角吹气。参考材料是经过类似处理但在静止空气中自然冷却的样品。微观结构测试表明，所有样品都有明显的晶粒细化，风冷搅拌摩擦加工的样品晶粒细化程度更高。对于自然冷却的样品，近表面区域的平均晶粒尺寸为7.6 µm，而对于风冷样品，45°气流变体的平均晶粒尺寸为1.4 µm，90°气流变体的平均晶粒尺寸为3.2 µm。晶粒细化程度更高的一个结果是，风冷搅拌摩擦加工样品的硬度高于自然冷却样品。只有在风冷搅拌摩擦加工的试样中，耐磨性能才得到改善。研究发现，吹气角度的变化不仅会影响搅拌区的晶粒细化程度，还会影响表面的几何结构。在所有样品中，搅拌摩擦加工导致金属间析出相重新分布，并伴有它们在基体中的部分溶解。
