Topic
Liquation
About: Liquation is a research topic. Over the lifetime, 575 publications have been published within this topic receiving 7900 citations.
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Journal Article•
TL;DR: In this article, the authors investigated liquation cracking in the partially melted zone (PMZ) in welds of Al-Si alloys, which are widely used as casting alloys and often rich in Si to ensure good castability.
Abstract: Liquation cracking was investigated in the partially melted zone (PMZ) in welds of Al-Si alloys, which are widely used as casting alloys and often rich in Si to ensure good castability Alloy A357 (Al-7Si) was selected as an example for studying liquation cracking in castings repaired or joined by welding The crack susceptibility was evaluated by the circular-patch test, and full penetration, gas metal arc welds made with filler metals 1100 (Al), 4043 (Al-5Si), 4047 (Al-12Si), and 5356 (Al-5Mg) The PMZ consisted of a dendrites and interdendritic eutectic similar to the base metal, and the interdendritic eutectic coarsened and became a and Si particles in the heat-affected zone(HAZ) Liquation cracking was significant with filler metals 1100 and 5356 but slight with filler metals 4043 and 4047 Based on the multicomponent Scheil model and including as many as 10 different elements, curves of temperature (T) vs fraction solid (f S ) were calculated for the weld metal and the PMZ, which arc competing with each other in increasing f S , and hence crack resistance It is proposed that liquation cracking can occur if the weld-metal f S > the PMZ f S during the last 40°C of PMZ solidification before f S reaches 099 (beyond which there is too little grain-boundary liquid to cause liquation cracking) It was found that in welds with significant liquation cracking (filler metals 1100 and 5356), the weld-metal f S was significantly higher in the temperature range, while in welds with slight liquation cracking (filler metals 4043 and 4047), it was only slightly higher In all welds, liquation cracks were completely backfilled and healed, instead of open as in full penetration welds of wrought aluminum alloys, such as Alloys 2219 and 6061 The T-f S curves showed that, as compared to Alloys 2219 and 6061, Alloy A357 had a much higher fraction liquid (1 - f S ) for backfilling before PMZ solidification was essentially over (f S = 099) The T-f S curves were also calculated for two other high-Si, Al-Si casting alloys, A356 and 359, and the fraction liquid was high before PMZ solidification was essentially over, thus suggesting a strong tendency for backfilling and healing
78 citations
TL;DR: In this article, the tensile properties of thixoextruded components are determined and compared with those of AZ80 magnesium alloy from starting material produced by casting, and the results show that with increasing number of RUE passes solid grain size decreases and the rate of liquation is improved.
77 citations
Journal Article•
TL;DR: In this article, the microstructure of aluminum alloy 2219 was examined in the partially melted zone (PMZ), which is a narrow region immediately outside the fusion zone, and extensive liquation was observed at three different locations: at large {theta} (Al{sub 2}Cu) particles, along grain boundaries (GBs) and at numerous isolated points within grains.
Abstract: Aluminum Alloy 2219 was welded by gas metal arc welding and the microstructure was examined in the partially melted zone (PMZ), which is a narrow region immediately outside the fusion zone. Extensive liquation was observed at three different locations: at large {theta} (Al{sub 2}Cu) particles, along grain boundaries (GBs) and at numerous isolated points within grains. Liquation was initiated at the eutectic temperature T{sub E}, by the eutectic reaction {alpha} + {theta} {r_arrow} L{sub E} and intensified by further melting, above T{sub E}, of the {alpha} matrix surrounding the eutectic liquid (L{sub E}). The microstructure of the liquated-and-solidified GB material is intriguing. First, the material consisted of a new GB of mostly thin, divorced eutectic and a eutectic-free strip of {alpha} immediately next to it. Second, within an individual grain, the strip was along the top and the side facing the weld. Third, with respect to the weld, the strip was always behind the new GB. These three characteristics point to an important phenomenon, that is, solidification of the liquated GB is directional - upward and toward the weld, as a result of the temperature gradients across the PMZ. A thin, brittle eutectic GB and a soft ductile {alpha} stripmore » side by side are expected to be much weaker than a normal GB before welding.« less
75 citations
TL;DR: In this article, the authors investigated the cracking mechanism in the overlapping zone (OZ) of laser solid forming (LSF) of IN-738LC alloy and found that both the solidification cracks and liquation cracks can be found in the OZ of the LSFed IN- 738LC specimen, and the results showed that the cracks always propagated along the high-angle grain boundaries due to their relatively wider solidification temperature range compared with the lower angle grain boundaries.
73 citations
TL;DR: The results show transgranular fracture can also occur in metallic alloys in semi-solid state and this refinement, previously attributed to fragmentation of secondary arms by melt-shearing, is also controlled by an additional TLC mechanism.
Abstract: Grain refinement via semi-solid deformation is desired to obtain superior mechanical properties of cast components. Using quantitative in situ synchrotron X-ray tomographic microscopy, we show an additional mechanism for the reduction of grain size, via liquation assisted transgranular cracking of semi-solid globular microstructures. Here we perform localized indentation of Al-15wt.%Cu globular microstructures, with an average grain size of ∼480 μm, at 555 °C (74% solid fraction). Although transgranular fracture has been observed in brittle materials, our results show transgranular fracture can also occur in metallic alloys in semi-solid state. This transgranular liquation cracking (TLC) occurs at very low contact stresses (between 1.1 and 38 MPa). With increasing strain, TLC continues to refine the size of the microstructure until the grain distribution reaches log-normal packing. The results demonstrate that this refinement, previously attributed to fragmentation of secondary arms by melt-shearing, is also controlled by an additional TLC mechanism.
69 citations