TY - JOUR

T1 - High temperature strength and hot working technology for As-cast Mg-1Zn-1Ca (ZX11) alloy

AU - Rao, Kamineni Pitcheswara

AU - Suresh, Kalidass

AU - Prasad, Yellapregada Venkata Rama Krishna

AU - Dharmendra, Chalasani

AU - Hort, Norbert

AU - Dieringa, Hajo

N1 - Acknowledgments: This work was fully supported by a research grant (General Research Fund, Project #11259116) from the Research Grants Council of the Hong Kong Special Administrative Region.

PY - 2017/10/1

Y1 - 2017/10/1

N2 - Cast Mg-1Zn-1Ca alloy (ZX11) has been tested to evaluate its compressive strength between 25 °C and 250 °C, and workability in the range of 260-500 °C. The ultimate compressive strength of this alloy is about 30% higher than that of creep-resistant alloy Mg-3Sn-2Ca (TX32) between 25 °C and 200 °C, and exhibits a plateau between 100 °C and 175 °C, similar to TX32. This is attributed to Mg2Ca particles present at grain boundaries that reduce their sliding. The processing map, developed between 260 and 420 °C in the strain rate limits of 0.0003 s-1 to 1 s-1, exhibited two domains in the ranges: (1) 280-330 °C and 0.0003-0.01 s-1 and (2) 330-400 °C and 0.0003-0.1 s-1. In these domains, dynamic recrystallization occurs, with basal slip dominating in the first domain and prismatic slip in the second, while the recovery mechanism being climb of edge dislocations in both. The activation energy estimated using standard kinetic rate equation is 191 kJ/mol, which is higher than the value for lattice self-diffusion in magnesium indicating that a large back stress is created by the presence of Ca2Mg6Zn3 intermetallic particles in the matrix. It is recommended that the alloy be best processed at 380 °C and 0.1 s-1 at which prismatic slip is favored due to Zn addition. At higher strain rates, the alloy exhibits flow instability and adiabatic shear band formation at <340 °C while flow localization and cracking at grain boundaries occurs at temperatures >400 °C.

AB - Cast Mg-1Zn-1Ca alloy (ZX11) has been tested to evaluate its compressive strength between 25 °C and 250 °C, and workability in the range of 260-500 °C. The ultimate compressive strength of this alloy is about 30% higher than that of creep-resistant alloy Mg-3Sn-2Ca (TX32) between 25 °C and 200 °C, and exhibits a plateau between 100 °C and 175 °C, similar to TX32. This is attributed to Mg2Ca particles present at grain boundaries that reduce their sliding. The processing map, developed between 260 and 420 °C in the strain rate limits of 0.0003 s-1 to 1 s-1, exhibited two domains in the ranges: (1) 280-330 °C and 0.0003-0.01 s-1 and (2) 330-400 °C and 0.0003-0.1 s-1. In these domains, dynamic recrystallization occurs, with basal slip dominating in the first domain and prismatic slip in the second, while the recovery mechanism being climb of edge dislocations in both. The activation energy estimated using standard kinetic rate equation is 191 kJ/mol, which is higher than the value for lattice self-diffusion in magnesium indicating that a large back stress is created by the presence of Ca2Mg6Zn3 intermetallic particles in the matrix. It is recommended that the alloy be best processed at 380 °C and 0.1 s-1 at which prismatic slip is favored due to Zn addition. At higher strain rates, the alloy exhibits flow instability and adiabatic shear band formation at <340 °C while flow localization and cracking at grain boundaries occurs at temperatures >400 °C.

KW - Biomaterial

KW - Compressive strength

KW - Finite element simulation

KW - Hot forging

KW - Hot workability

KW - Kinetic analysis

KW - Mg-Zn-Ca alloy

KW - Microstructure

KW - Processing map

KW - Engineering

UR - http://www.scopus.com/inward/record.url?scp=85031301152&partnerID=8YFLogxK

U2 - 10.3390/met7100405

DO - 10.3390/met7100405

M3 - Journal articles

AN - SCOPUS:85031301152

VL - 7

JO - Metals

JF - Metals

SN - 2075-4701

IS - 10

M1 - 405

ER -