Solidification Crack Susceptibility of Aluminum Alloy Weld Materials (Report I)
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For the purpose of quantitative investigation of solidification crack susceptibility for aluminum alloys, the properties of the ductility curve in solidification range, such as the brittleness temperature range (BTR), the minimum value of ductility within BTR (E_<min>), and the shape of the ductility curve against temperature drop were investigated by Trans-Varestraint test for Al-Mg and Al-Cu binary alloys contained a small amount of Fe and commercially used aluminum alloys of 1xxx, 2xxx and 5xxx types. The main conclusions obtained are as follows: (1) The BTR is gradually increased with an increase of alloying elements, and then is satulated to the temperature difference between liquidus and ternary eutectic temperature irrespective of an increase of alloying elements when the ternary eutectic of Al-Mg-Fe or Al-Cu-Fe system begin to form. (2) The E_<min> is very low for almost all alloys used with the exception of commercially pure aluminum. There are below zero augmented strain for Al-0.8%Cu and -2%Cu binary alloys and within the range from zero to 0.1% for the other alloys, while within the range from 0.1 to 0.3% for commercially pure aluminum. (3) The minimum in the ductility curve in the BTR is generally observed in the location just behind the liquidus temperature, and then the crack begins to start there during Trans-Varestraint test. (4) The mode of the fractured surface of the solidification crack which is generated by Trans-Varestraint test is gradually changed with a decrease of temperature as a result of a scanning electron microscopic investigation and it could be classified into three types, that is, called type D, type D-F and type F in order of a degrease of temperature from the near liquidus temperature to the temperature of lower limit of the BTR.
- Trans. of JWRI
Trans. of JWRI 5-2, 53-67, 1976