TY - JOUR
T1 - Microstructure and properties of twinned dendrites in directionally solidified A356 alloy
AU - Li, Yang
AU - Li, Shuangming
AU - Yang, Luyan
AU - Zhong, Hong
N1 - Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/9/12
Y1 - 2018/9/12
N2 - Twinned dendrites and regular dendrites have been respectively produced in A356 alloy by Bridgman solidification. The primary trunks of twinned dendrites grew along <110> direction and were split by a coherent (111) twin plane were characterized by electron backscattered diffraction (EBSD), which is different from the <100> regular dendrites. The growth of twinned dendrites was found to have a rotation relationship around a common <110> direction. With respect to the specimens with regular dendrites, the mean tensile strength, elongation and toughness of the specimens with twinned dendrites were increased from 230 MPa to 239 MPa, 16.69–18.99%, 34.45 J/m3 to 40.88 J/m3, respectively. Meanwhile, the coefficient of thermal expansion (CTE) of the specimen with twinned dendrites increase monotonically up to 2.28×10−5K−1 at temperature of 473 K. This CTE was successfully lowered than that of specimen with regular dendrites at the temperature above 323 K, and reaches the maximum decrease around 4.2% at 473 K. The fractures of two types of specimens were both originated from the Si-rich regions where dimples formed. In addition, detailed analyses on coherent twin boundary (CTB) of twinned dendrites by transmission electron microscope (TEM) and high-resolution TEM (HRTEM) indicate that the mechanisms of twin and dislocation-CTB interactions can enhance the strength and ductility of the A356 alloy with twinned dendrites.
AB - Twinned dendrites and regular dendrites have been respectively produced in A356 alloy by Bridgman solidification. The primary trunks of twinned dendrites grew along <110> direction and were split by a coherent (111) twin plane were characterized by electron backscattered diffraction (EBSD), which is different from the <100> regular dendrites. The growth of twinned dendrites was found to have a rotation relationship around a common <110> direction. With respect to the specimens with regular dendrites, the mean tensile strength, elongation and toughness of the specimens with twinned dendrites were increased from 230 MPa to 239 MPa, 16.69–18.99%, 34.45 J/m3 to 40.88 J/m3, respectively. Meanwhile, the coefficient of thermal expansion (CTE) of the specimen with twinned dendrites increase monotonically up to 2.28×10−5K−1 at temperature of 473 K. This CTE was successfully lowered than that of specimen with regular dendrites at the temperature above 323 K, and reaches the maximum decrease around 4.2% at 473 K. The fractures of two types of specimens were both originated from the Si-rich regions where dimples formed. In addition, detailed analyses on coherent twin boundary (CTB) of twinned dendrites by transmission electron microscope (TEM) and high-resolution TEM (HRTEM) indicate that the mechanisms of twin and dislocation-CTB interactions can enhance the strength and ductility of the A356 alloy with twinned dendrites.
KW - A356 alloy
KW - Coherent twin boundary
KW - Mechanical properties
KW - Thermal expansion
KW - Twinned dendrites
UR - http://www.scopus.com/inward/record.url?scp=85050465505&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2018.07.079
DO - 10.1016/j.msea.2018.07.079
M3 - 文章
AN - SCOPUS:85050465505
SN - 0921-5093
VL - 734
SP - 7
EP - 19
JO - Materials Science and Engineering: A
JF - Materials Science and Engineering: A
ER -