Effect of grain size and structure, solid solution elements, precipitates and twinning on nanohardness of Mg-Re alloys
Research output: Contributions to collected editions/works › Article in conference proceedings › Research › peer-review
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Effect of grain size and structure, solid solution elements, precipitates and twinning on nanohardness of Mg-Re alloys. / Maier, Petra; Richter, Asta; Tober, Gerhard et al.
Light Metals Technology 2013. ed. / Ian Stone; Brian McKay; Zhongyun Fan. Trans Tech Publications Ltd, 2013. p. 491-495 (Materials Science Forum; Vol. 765).Research output: Contributions to collected editions/works › Article in conference proceedings › Research › peer-review
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TY - CHAP
T1 - Effect of grain size and structure, solid solution elements, precipitates and twinning on nanohardness of Mg-Re alloys
AU - Maier, Petra
AU - Richter, Asta
AU - Tober, Gerhard
AU - Hort, Norbert
N1 - Conference code: 6
PY - 2013/7
Y1 - 2013/7
N2 - In this study Mg10GdxNd alloys are investigated by nanoindentation hardness measurements in several material conditions. Mg10GdxNd alloys with an average coarse grain size of 500 μm were cast by permanent mold direct chill casting. Hardness values vary due to the inhomogeneous microstructure formed during the solidification process consisting of dendrite arms with preferred orientation direction. The effect of dissolving particles during solution heat treatment (T4) and isothermal ageing (T6) was observed to a different extent depending on Nd content. Isothermal ageing promotes a duplex microstructure of coarse β1 phase precipitates and regions containing much finer precipitates. Post processing by direct extrusion changes the microstructure dramatically to an average grain size of 15 μm. The microstructure after hot extrusion shows segregation of precipitates in the extrusion direction. Near this alignment of second phases hardness and plastic deformation differ from precipitates enriched in RE elements due to depleted regions of solid solution around them. This phenomenon is known from alloying element segregation to grain boundaries. Depending on the amount and location of second phases in the as-cast microstructure and degree of cold work, recrystallization leads to an inhomogeneous microstructure, consisting of fine grains (15 μm) and very fine grains, where second phases act as nuclei during the recrystallization process. Furthermore, mechanical testing (fatigue) causes an increase in dislocation density by work hardening and extensive twinning near the fractured surface. Here the hardening effect interferes with grain size strengthening.
AB - In this study Mg10GdxNd alloys are investigated by nanoindentation hardness measurements in several material conditions. Mg10GdxNd alloys with an average coarse grain size of 500 μm were cast by permanent mold direct chill casting. Hardness values vary due to the inhomogeneous microstructure formed during the solidification process consisting of dendrite arms with preferred orientation direction. The effect of dissolving particles during solution heat treatment (T4) and isothermal ageing (T6) was observed to a different extent depending on Nd content. Isothermal ageing promotes a duplex microstructure of coarse β1 phase precipitates and regions containing much finer precipitates. Post processing by direct extrusion changes the microstructure dramatically to an average grain size of 15 μm. The microstructure after hot extrusion shows segregation of precipitates in the extrusion direction. Near this alignment of second phases hardness and plastic deformation differ from precipitates enriched in RE elements due to depleted regions of solid solution around them. This phenomenon is known from alloying element segregation to grain boundaries. Depending on the amount and location of second phases in the as-cast microstructure and degree of cold work, recrystallization leads to an inhomogeneous microstructure, consisting of fine grains (15 μm) and very fine grains, where second phases act as nuclei during the recrystallization process. Furthermore, mechanical testing (fatigue) causes an increase in dislocation density by work hardening and extensive twinning near the fractured surface. Here the hardening effect interferes with grain size strengthening.
KW - Dendrites
KW - Grain size
KW - Mg-RE alloys
KW - Precipitates
KW - Twinning
KW - Engineering
UR - http://www.scopus.com/inward/record.url?scp=84883039253&partnerID=8YFLogxK
UR - https://www.mendeley.com/catalogue/8a85a9c1-b298-3dce-b320-f82c3ba1cd9a/
U2 - 10.4028/www.scientific.net/MSF.765.491
DO - 10.4028/www.scientific.net/MSF.765.491
M3 - Article in conference proceedings
AN - SCOPUS:84883039253
SN - 9783037857663
T3 - Materials Science Forum
SP - 491
EP - 495
BT - Light Metals Technology 2013
A2 - Stone, Ian
A2 - McKay, Brian
A2 - Fan, Zhongyun
PB - Trans Tech Publications Ltd
T2 - 6th International Light Metals Technology Conference - LMT 2013
Y2 - 24 July 2013 through 26 July 2013
ER -