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Институт проблем сверхпластичности металлов РАН, ул. Халтурина 39, 450001 Уфа Ключевые слова: жидкая штамповка, алюминиевый сплав, структура, механические свойства.

The effect of severe plastic deformation by high pressure torsion (HPT) on the structure of AK12MMgN-18 %SiCp composite alloy was investigated. A liquid-forged billet was taken as an initial material. Samples 8 mm in diameter and 0.45 mm in thickness were deformed by torsion in a Bridgman anvil at room temperature up to 5 turns under the pressure of 4 GPa. After deformation the samples were annealed in the temperature range of 300 -500°C for 5 minutes. The average area and volume fraction of particles in the initial, HPT-processed and annealed samples were evaluated. The change of the concentration level of a solid solution in the states under study was analyzed. It was shown that HPT led to a fragmentation of particles and a reduction of their average area: silicon particles from 4.4 ± 0.1 to 0.32 ± 0.02 μm 2 , intermetallic particles from 5.2 ± 2.6 to 0.20 ± 0.02 μm 2 , and SiC from 37.6 ± 0.9 to 3.9 ± 0.02 μm 2 . At the same time, a partial dissolution of excess phases occurred that resulted in the formation of a supersaturated solid solution. Post-HPT annealing led to a dissolution of the supersaturated solid solution with a separation of secondary phases of different morphology not typical to the alloy: globular silicon, rod shaped phase enriched by Ni, Si and Fe and a more compact phase containing Si and Cu. The higher the annealing temperature, the more intensive was the process of supersaturated solid solution decomposition and the higher was the volume fraction of silicon and intermetallic particles. Their average area increased with annealing temperature. No changes in the average area and volume fraction of SiC particles during annealings of HPT-processed alloy were observed. Исследовано влияние интенсивной пластической деформации, реализованное кручением под высоким давлением на структуру композиционного сплава АК12ММгН-18 %SiCp. Исходным материалом служила жидкоштампованная заготовка. Образцы диаметром 8 мм и толщиной 0,45 мм деформировали при комнатной температуре на наковаль-не Бриджмана кручением на 5 оборотов при давлении 4 ГПа. После деформации образцы отжигали в интервале температур 300…500°С в течение 5 минут. Оценивали среднюю площадь и объемную долю первичных и вторичных фаз, а также частиц SiC в исходном, деформированном и отоженном образцах. Проанализировали изменение ле-гированности твердого раствора в исследуемых состояниях. Показано, что интенсивная пластическая деформация привела к дроблению присутствующих в сплаве частиц, средний размер которых уменьшался: кремния с 4,4 ± 0,1 до 0,32 ± 0,02 мкм 2 , интерметаллидных фаз с 5,2 ± 2,6 до 0,20 ± 0,02 мкм 2 , SiC с 37,6 ± 0,9 до 3,9 ± 0,02 мкм 2 . При этом произошло частичное растворение избыточных фаз, что способствовало формированию пересыщенного твердого раствора. Последующий отжиг привел к распаду пересыщенного алюминиевого твердого раствора с выделением нетипичных для сплава вторичных фаз различной морфологии: глобулярного кремния, стержнеобразной фазы, обогащенной Ni, Si и Fe и более компактной фазы, содержащей Si и Cu. При этом, чем...

Friction stir processing (FSP) and standard hardening T6 heat treatment were applied for local surface hardening of the АК12D aluminum (Al-12.8Si-1.67Cu-1.03Ni-0.84Mg-0.33Mn-0.23Co-0.24Fe) alloy plates obtained by hot-compression at elevated temperature. FSP was carried out by introducing a pin into the bulk of the material, followed by its movement along the surface at a traverse speed of 8 and 16 mm / min, accompanied by rotation of the pin at a speed of 2000 rpm. The effect of FSP parameters and T6 treatment on structure and hardness were investigated. It was established that FSP at 2000 rpm and 8 mm / min speed resulted in the formation of a monolithic and defect-free processing zone. The FSP and T6 treatment led to fragmentation of the primary Si and intermetallic phases and partial dissolution of intermetallic phases in the α-Al solid solution followed by decomposition and the formation of dispersed precipitates. The formation of a quasi-equiaxed finegrained structure was observed after FSP and T6 heat treatment in the stir zone. The measured Brinell hardness demonstrated an average value of 128 HB after treatment versus 103 HB in the initial state. The work reveals the features of the local surface structure refinement allowing to figure out approaches to the design of constructions with enhanced properties.