Mechanical properties of biocompatible Y-TZP/Al2O3 composites obtained from mechanically alloyed powders

• Published in: Journal of the Brazilian Society of Mechanical Sciences and Engineering Vol. 42; no. 7
• Main Authors: de Freitas, Bruno Xavier, Alves, Manuel Fellipe R. Pais, Santos, Claudinei, Ramos, Alfeu Saraiva, Ramos, Erika Coaglia Trindade, Strecker, Kurt
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-07-2020; Springer Nature B.V
• Subjects: Alloy development; Alloy powders; Aluminum oxide; Argon; Ball milling; Ball mills; Bend strength; Biocompatibility; Composite materials; Crystallites; Densification; Engineering; Flexural strength; Fracture toughness; Grain size; Heat treating; Mechanical alloying; Mechanical Engineering; Mechanical properties; Microstructure; Modulus of rupture in bending; Phase composition; Sinterability; Sintering; Sintering (powder metallurgy); Technical Paper; Tetragonal zirconia polycrystals; Transformation toughening; Yttria-stabilized zirconia; Yttrium oxide; Mechanical properties; Y-TZP/Al; Mechanical alloying; composite; O; Processing
• ISSN: 1678-5878; 1806-3691
• DOI: 10.1007/s40430-020-02431-1

In this study, an alumina-toughened zirconia composite (ATZ) was developed from mechanical alloyed nano-scale powder mixtures using low-sintering temperatures. A powder mixture, composed of 80 wt.% Y-TZP, ZrO
2
(3 mol.% Y
2
O
3
), and 20 wt.% Al
2
O
3
, was prepared by mechanical alloying (MA) in a planetary ball mill under argon atmosphere, with milling times of up to 60 h, using a rotary speed of 200 rpm and a ball-to-powder weight ratio of 10:1. The mixtures were compacted at 100 MPa and sintered at 1400 °C—2 h. In the milled powders, the crystallite size of the ZrO
2
matrix was reduced from 130 to 40 Å, when increasing the milling time from 1 to 60 h. After sintering, the samples were characterized by its phase composition, microstructure, relative density, fracture toughness and biaxial flexural strength. Fully dense samples were obtained after sintering the powder-mixture milled for 60 h at 1400 °C—2 h. In comparison, the conventional powder-mixture achieved high densification only after sintering at 1600 °C—2 h. Sintered samples prepared with mechanical alloyed powder mixtures presented a fracture toughness (
K
IC
) of 8.2 ± 0.3 MPa m
1/2
and a bending strength of 880 ± 45 MPa, significantly higher compared to samples prepared from the conventional processed powder mixture sintered at 1600 °C—2 h, presenting a
K
IC
of 6.7 ± 0.5 MPam
1/2
and a bending strength of 697 ± 85 MPa. The improved mechanical strength of the composites prepared from mechanical alloyed powders is attributed to the increased sinterability of these powders, allowing full densification at 1400 °C, and also resulting in a reduction in the tetragonal ZrO
2
grain size. Thus, a larger population of these grains is formed in the microstructure, increasing fracture toughness and strength by the tetragonal to monoclinic phase transformation toughening mechanism.