Effects of annealing and extrusion on the microstructure and tensile properties of ultrafine-grained Al fabricated by spark plasma sintering. (20th October 2021)

• Record Type: Journal Article
• Authors: Cao, Lei; Xie, Yuehuang; Luo, Yifei; Liang, Jiamiao; Wang, Jun; Zhang, Deliang; Wang, Limin
• Is Part Of: Powder metallurgy. Volume 64:Number 5(2021)
• Page Start: 412
• Page End: 424
• Publication Date: 2021-10-20
• Subjects: Spark plasma sintering -- interparticle boundaries -- annealing -- hot extrusion -- heterogeneous structure -- mechanical properties; Powder metallurgy -- Periodicals; 671.3705
• DOI: 10.1080/00325899.2021.1928814
• Languages: English
• ISSNs: 0032-5899

Abstract

ABSTRACT: Ultrafine-grained Al samples were fabricated by spark plasma sintering (SPS) of a mechanically milled nanocrystalline powder. The effects of annealing and extrusion on the microstructure and tensile properties of the as-SPSed samples were investigated. Annealing removed the nanopores and caused significant coarsening of Al grains in the interparticle boundary (IPB) regions, leading to the formation of a heterogeneous structure consisting of coarse grains, ultrafine grains and Al4 C3 /Al2 O3 nanoparticles. Hot extrusion also eliminated the nanopores and resulted in the formation of a heterogeneous structure containing enhanced volume fraction of ultrafine grains and finer nanoparticles. These microstructural changes rendered a much improved YS and UTS of 251 and 288 MPa, respectively, and excellent tensile ductility (elongation to fracture: 12.7%). The improvement in mechanical properties can be attributed to grain boundary and nanoparticle strengthening, strain delocalisation of the heterogeneous structure and improvement of the bonding strength of IPBs.