TY - CHAP

T1 - Twinning assisted crack propagation of magnesium-rare earth casting and wrought alloys under bending

AU - Maier, Petra

AU - Mendis, Chamini

AU - Wolff, Martin

AU - Müller, Sören

AU - Hort, Norbert

N1 - Conference code: 7

PY - 2015

Y1 - 2015

N2 - Due to their high specific strength, good corrosion resistance and high temperature strength Magnesium alloys containing Rare Earth additions are promising candidates for structural and engine applications in the transportation industry. Also medical applications, like bone screws and nails, benefit from their moderate corrosion rate and biocompatibility. All applications need materials which show a high strength, ductility and fracture toughness in case a crack has formed during service to keep safety against rupture. In this study four extruded Mg10Gd based alloys modified with Nd and La have been 3-point-bend tested at low a deformation speed to evaluate the influence of the microstructure on crack growth. A comparison to the cast material (subjected to T4 to increase ductility and to reduce the dendritic microstructure) shows an increase in strength and ductility due to the fine grained microstructure as a result of recrystallization during extrusion. The maximum bending strength and outer strain to crack initiation is also strongly influenced by the alloying system itself. The influence of Nd and La to the binary alloy Mg10Gd is discussed in using tensile, compression and bending tests. The increase in strength results in reduced elongation to fracture in tension loading as well as the outer strain for the crack initiation during bending tests. Tensile tests are often discussed to be not a reliable method for determining the Young’s modulus of Magnesium. Therefore resonance frequency damping analysis has been applied to determine the dynamic modulus of elasticity, which is compared with the flexural (bending) modulus. Crack growth is discussed using light microscopy and correlated with bending stress-strain curves. The crack growth rate of the extruded, fine grained material is many times higher than of the cast, coarse grained material. Crack propagation is mostly transgranular and assisted by twinning.

AB - Due to their high specific strength, good corrosion resistance and high temperature strength Magnesium alloys containing Rare Earth additions are promising candidates for structural and engine applications in the transportation industry. Also medical applications, like bone screws and nails, benefit from their moderate corrosion rate and biocompatibility. All applications need materials which show a high strength, ductility and fracture toughness in case a crack has formed during service to keep safety against rupture. In this study four extruded Mg10Gd based alloys modified with Nd and La have been 3-point-bend tested at low a deformation speed to evaluate the influence of the microstructure on crack growth. A comparison to the cast material (subjected to T4 to increase ductility and to reduce the dendritic microstructure) shows an increase in strength and ductility due to the fine grained microstructure as a result of recrystallization during extrusion. The maximum bending strength and outer strain to crack initiation is also strongly influenced by the alloying system itself. The influence of Nd and La to the binary alloy Mg10Gd is discussed in using tensile, compression and bending tests. The increase in strength results in reduced elongation to fracture in tension loading as well as the outer strain for the crack initiation during bending tests. Tensile tests are often discussed to be not a reliable method for determining the Young’s modulus of Magnesium. Therefore resonance frequency damping analysis has been applied to determine the dynamic modulus of elasticity, which is compared with the flexural (bending) modulus. Crack growth is discussed using light microscopy and correlated with bending stress-strain curves. The crack growth rate of the extruded, fine grained material is many times higher than of the cast, coarse grained material. Crack propagation is mostly transgranular and assisted by twinning.

KW - Bending

KW - Crack propagation

KW - Magnesium-rare earth alloys

KW - Twinning

KW - Engineering

UR - http://www.scopus.com/inward/record.url?scp=84954472009&partnerID=8YFLogxK

U2 - 10.4028/www.scientific.net/MSF.828-829.311

DO - 10.4028/www.scientific.net/MSF.828-829.311

M3 - Article in conference proceedings

AN - SCOPUS:84954472009

SN - 9783038355625

T3 - Materials Science Forum

SP - 311

EP - 317

BT - Light Metals Technology 2015

A2 - Chikwanda, Hilda K.

A2 - Chikosha, Silethelwe

PB - Trans Tech Publications Ltd

T2 - 7th International Light Metals Technology Conference, LMT 2015

Y2 - 27 July 2015 through 29 July 2015

ER -