Quasicrystal phase evolution and mechanical properties of Mg-3.5Zn-0.6Gd alloy processed by high-pressure torsion

Tc explore the effect -f lngh yressure torsion (HPT) n thc icosnlieurai ciiasinyetal piiase ti-pliase), the .iota J upsilon rosunn iota sigma e evoiuLon and niechanicai property of extruded Mg-3.5Zn-0.6Gd alloy after HPT were investigated in detail. The residts showed that a large density of twins and dislocation were generated diiring HPT, which effectively promoted the rnicrostructiire refinenient. The block-shaped I-phase was broken into chain stnict iota sigma e and gradiially evolved into umuda- 1-phase with the increasing strain. The block and graniilar I-phase through HPT exhibited a niore evenly disti'ibution. After HPT for'', turns, the average gram size was refined to roimd about 89 nrn and niicrohaidness reached to a niaxiniiim value abant 119 HV. The 2-fold syrnrnetry of icosahedral giiasiciystal phase (I-phase) was unveiled by TEM. According to the HRTEM and IFNT, the [il 0]Mg//[2-fold]i.phase and (o002)Mg//(2-fold)t.phase can be identified in the Mg-3.5Zn-0.6Gd alloy. The dislocation and defect with an angle nearly 135 degrees were also observed after HPT for 9 tiuns. With the fiuther increase of strain, the niicrohardness appeared to decrease due to the dissolution of granular I-phase. The niodiied strength niechanisni was constnicted to distinguish the conuibution of gram boi nda y, dislocation and precipitates.