TY - JOUR
T1 - Development of an elasto-viscoplastic constitutive equation for an al-mg alloy undergoing a tensile test during partial solidification
AU - Takai, Ryosuke
AU - Matsushita, Akira
AU - Yanagida, Shogo
AU - Nakamura, Koichiro
AU - Yoshida, Makoto
PY - 2015
Y1 - 2015
N2 - Predicting hot tearing during direct chill casting using thermal stress analysis requires constitutive equations in both semi-solid state and below the solidus of the alloy. However, numerous difficulties have been hindered constitutive equations used heretofore for hot tearing predictions. (1) Testing methods for obtaining material constants were inappropriate. First, the elastic strain reversibility was unconfirmed. Second, a flat distribution of temperature in the specimen gauge length was not guaranteed. Third, strain was measured not from local strain but from cross-head displacement. Fourth, the melt-back phenomenon was unavoidable in test during partial remelting because of homogenization of the segregation structure. (2) Temperature dependence of the strain-rate sensitivity of stress was not considered. (3) Some material constants were inferred, not obtained experimentally. This study developed elasto-viscoplastic constitutive equations (Hooke's and viscoplastic Norton-Hoff laws) for partially solidified state and below the solidus. To obtain material constants experimentally, two tensile tests for which issue (1) was addressed were conducted using Al-5 mass%Mg alloy. They were a tensile test after partial solidification and high-temperature tensile test with high-frequency induction coil. After the temperature dependence of elastic and viscoplastic properties was investigated, material constants were obtained and were compared with those obtained using earlier testing methods.
AB - Predicting hot tearing during direct chill casting using thermal stress analysis requires constitutive equations in both semi-solid state and below the solidus of the alloy. However, numerous difficulties have been hindered constitutive equations used heretofore for hot tearing predictions. (1) Testing methods for obtaining material constants were inappropriate. First, the elastic strain reversibility was unconfirmed. Second, a flat distribution of temperature in the specimen gauge length was not guaranteed. Third, strain was measured not from local strain but from cross-head displacement. Fourth, the melt-back phenomenon was unavoidable in test during partial remelting because of homogenization of the segregation structure. (2) Temperature dependence of the strain-rate sensitivity of stress was not considered. (3) Some material constants were inferred, not obtained experimentally. This study developed elasto-viscoplastic constitutive equations (Hooke's and viscoplastic Norton-Hoff laws) for partially solidified state and below the solidus. To obtain material constants experimentally, two tensile tests for which issue (1) was addressed were conducted using Al-5 mass%Mg alloy. They were a tensile test after partial solidification and high-temperature tensile test with high-frequency induction coil. After the temperature dependence of elastic and viscoplastic properties was investigated, material constants were obtained and were compared with those obtained using earlier testing methods.
KW - Aluminum alloy
KW - Direct-chill casting
KW - Elasto-viscoplastic constitutive equation
KW - Hot tearing
KW - Solidification
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U2 - 10.2320/matertrans.L-M2015815
DO - 10.2320/matertrans.L-M2015815
M3 - Article
AN - SCOPUS:84938343358
VL - 56
SP - 1233
EP - 1241
JO - Materials Transactions
JF - Materials Transactions
SN - 1345-9678
IS - 8
ER -