Konsolidacija aluminijskog praha

master's thesis

• Title (english): Consolidation of Al-powder
• Author: Luka Radonić
• Mentor: Zdravko Schauperl (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2016-12-08, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Primjena metoda intenzivne plastične deformacije u metalurgiji praha može omogućiti proizvodnju cjelovitih djelova iz praha kao početne sirovine pri niskim temperaturama od konvencionalnih metoda. Niske temperature procesa omogućavaju smanjenje energije utrošene u procesu. Osim uštede energije, postupcima intenzivne plastične deformacije se dobivaju i bolja neka mehanička svojstva kao što su čvrstoća, tvrdoća i granica razvlačenja uz nešto nižu istezljivost u odnosu na lijevane uzorke. Još jedna od pozitivnih posljedica ovih postupaka jest i sitnozrnata mikrostruktura. U ovom radu je analiziran BP-ECAP postupak konsolidacije čistog aluminijskog praha. Hladno izostatički kompaktirani uzorci su provučeni kroz ECAP kalup kvadratnog presjeka kanala 12 mm x 12 mm koji se sjeku pod pravim kutom. Kompaktirani uzorci su imali tvrdoću od 37 HV0,2 i gustoću od 2,394 g/cm3 što je 89% teorijske gustoće aluminija, te prosječnu veličinu zrna od 90 μm. Uzorci su protiskivani brzinom klipa glavne preše od 8 mm/min na 100°C. Klip povratne preše se opirao gibanju sa 87 MPa preko površine od 144 mm2. Radi loših tolerancija alata, pojavilo se veliko trenje između umetka ispred klipa povratne preše i alata što je doprinijelo povećanju povratnog pritiska i pucanju alata. Nakon BP-ECAP konsolidacije, uzorak je imao usmjerenu mikrostrukturu u uzdužnom presjeku, te neusmjerenu u poprečnom presjeku. U uzdužnom presjeku je prosječna duljina zrna od 175 μm, a širina 54 μm što daje omjer duljine i širine od 3,2:1. Prosječna veličina zrna u poprečnom presjeku je 79 μm. Gustoća nakon BP-ECAP konsolidacije iznosi 2,517 g/cm3 što je 93,2% teorijske gustoće aluminija, a tvrdoća 49 HV0,2.

Abstract (english)

Application of sefere plastic deformation methods in powder metalurgy can make the production of bulk materials from powder possible on lower temperatures than conventional methods. Having lower process temperature means less energy consumption for the process. Except for the lower energy consumption, using severe plastic deformation methods can increase some of mechanical properties like strenght, hardness and yield strenght while elongation decreases in relation to casted ingots. Another advantage of this processes is fine grain microstructure. Consolidation of pure aluminium powder using BP-ECAP process is considered in this article. Cold isostatic compacted samples are pushed trough the ECAP tool with two square cross section 12 mm x 12 mm x 12 mm channels that intersect in 90°angle. Compacted samples had hardness of 37 HV0,2 and density of 2,394 g/cm3 which makes 89 % of teoretical density of aluminium with average grain size of 90 μm. Samples were pushed with main plunger speed of 8 mm/min at 100°C. Backpreassure plunger was opposing to motion with 87 MPa over 144 mm2 area. Because of the poor tool tolerances, there were a lot of friction between the mold and the insert that goes in front of the backpreassure plunger which contributed to the increased backpreassure and the tool failure. After BP-ECAP consolidation, samples microstructure was directed in longitudinal section and non directed in cross section. In longitudinal section, average grain lenght was 175 μm and average grain width was 54 μm which makes 3,2:1 lenght to width ratio. Average grain size in cross section was 79 μm. After BP-ECAP consolidation, sample had a density of 2,517 g/cm3 which is 93,2% of teoretical aluminium density and hardness of 49 HV0,2.

• Keywords: metalurgija praha; aluminij; prah; konsolidacija; ECAP; BP-ECAP; povratni pritisak; gustoća; teorijska gustoća; kompaktiranje; intenzivna plastična deformacija; usmjerenost mikrostrukture
• Keywords (english): powder metalurgy; aluminium; powder; consolidation; ECAP; BP-ECAP; backpreassure; density; teoretical density; compaction; severe plastic deformation; directed microstructure
• Language: croatian
• URN:NBN: urn:nbn:hr:235:618944
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-22 18:21:06