{"id":{"repo_id":"waikato-masters","oai_identifier":"oai:researchcommons.waikato.ac.nz:10289/4393"},"canonical_url":"https://search.dev.ndltd.org/etd/waikato-masters/oai:researchcommons.waikato.ac.nz:10289/4393","repository":{"repo_id":"waikato-masters","name":"University Waikato","base_url":"https://researchcommons.waikato.ac.nz/server/oai/request"},"display":{"title":"Microstructure, Thermal Stability and Consolidation of Nanostructured and Ultrafine Structured Cu based Metal Matrix Composite and Alloy Powders Produced by High Energy Mechanical Milling","abstract":"Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling. The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe. The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C. Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%. Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C.","abstract_html":"Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling. The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe. The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C. Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%. Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C.","abstract_has_math":false,"creators":["Mukhtar, Aamir"],"institution":"The University of Waikato","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Zhang, Deliang"],"committee_chairs":[],"committee_members":[],"year":2010,"date_issued":"2010","date_published":"2010","updated_at":"2026-07-24T05:57:18Z","subjects":["high energy mechanical milling","nanostructured materials","metal matrix composites","copper metal and alloys","heat treatment","powder consolidation","microstructural evolution","mechanical properties","powder processing"],"languages":[],"rights":["All items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Zhang, Deliang"]},{"key":"dc:creator","label":"Author","values":["Mukhtar, Aamir"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2010"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["The University of Waikato"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://hdl.handle.net/10289/4393"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["high energy mechanical milling","nanostructured materials","metal matrix composites","copper metal and alloys","heat treatment","powder consolidation","microstructural evolution","mechanical properties","powder processing"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["All items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://researchcommons.waikato.ac.nz/bitstreams/6b7f3898-aade-4120-a49a-b6774328b4ce/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling. The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe. The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C. Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%. Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["149275ba495b514aed8d2eb8c81bd40a","7cb602c6278253ba6db4c66bd192e8a1"]},{"key":"dc:title","label":"Title","values":["Microstructure, Thermal Stability and Consolidation of Nanostructured and Ultrafine Structured Cu based Metal Matrix Composite and Alloy Powders Produced by High Energy Mechanical Milling"]}]}],"canonical_facts":{"dc:contributor.advisor":["Zhang, Deliang"],"dc:creator":["Mukhtar, Aamir"],"dc:date.issued":["2010"],"dc:description.abstract":["Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling. The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe. The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C. Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%. Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C."],"dc:format.checksum.md5":["149275ba495b514aed8d2eb8c81bd40a","7cb602c6278253ba6db4c66bd192e8a1"],"dc:identifier.uri":["https://researchcommons.waikato.ac.nz/bitstreams/6b7f3898-aade-4120-a49a-b6774328b4ce/download"],"dc:publisher.institution":["The University of Waikato"],"dc:relation.isreferencedby":["https://hdl.handle.net/10289/4393"],"dc:rights":["All items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated."],"dc:subject":["high energy mechanical milling","nanostructured materials","metal matrix composites","copper metal and alloys","heat treatment","powder consolidation","microstructural evolution","mechanical properties","powder processing"],"dc:title":["Microstructure, Thermal Stability and Consolidation of Nanostructured and Ultrafine Structured Cu based Metal Matrix Composite and Alloy Powders Produced by High Energy Mechanical Milling"],"dc:type":["Thesis"]},"updated_at":"2026-07-24T05:57:18Z"}