China
Africa
Explore chapters and articles related to this topic
Corrosion and Protection
Published in Zainul Huda, Metallurgy for Physicists and Engineers, 2020
Liquid metal embrittlement (LME) refers to corrosion and/or embrittlement of a metal resulting from a coating of certain metals (e.g. aluminum, iron, copper, etc.) with a micron-thin layer of certain liquid metals (such as mercury, gallium, cadmium, etc.). LME promotes crack growth rate leading to brittle failure. For example, when certain aluminum alloys or brass are coated with mercury, a crack propagation rate of 500 cm/s has been reported (Hertzberg, 1996). LME can be avoided by the following techniques: (a) removal of liquid metal from the environment, (b) selection of compatible materials (e.g. Hg will embrittle Al but not Mg i.e. Hg-Mg is the set of compatible materials), (c) application of resistant coating to act as a barrier between the metal and the environment, and (d) chemical dissolution of the liquid metal (Huda et al., 2010).
Quantifying influence of LME inner cracks on joint strength of resistance spot weld
Published in Welding International, 2022
Kyohei Maeda, Reiichi Suzuki, Masao Hadano
In recent years, the application of high-strength steel sheets to car bodies has been progressing in order to achieve both weight reduction and collision safety in automobiles [1–3]. In order to achieve both strength and formability in high-strength steel sheets, alloy elements in the steel, such as C, Si, and Mn have inevitably increased [4,5]. Resistance spot welding (RSW) is widely used in automobile production lines, though it is well known that the range of appropriate welding conditions becomes narrower, and joint strength decreases as the elements increases [6,7]. Galvanized high-strength steel is particularly prone to occur liquid metal embrittlement (LME) cracking, or LME cracking caused by molten zinc [8–10]. As shown in Figure 1, LME cracking can be classified into outer cracking on the surface of the joint and inner cracking. Outer cracking occurs under a higher current or longer welding time conditions [11], while inner cracking generates when there is a tilt angle, electrode misalignment, and gap between sheets or an electrode and sheet [12,13]. It was also reported that the LME cracking can be prevented by controlling the current pattern, holding time, or electrode shape [12,14–16].
Recent progress and scientific challenges in multi-material additive manufacturing via laser-based powder bed fusion
Published in Virtual and Physical Prototyping, 2021
Some researchers (Liu et al. 2014; Chen et al. 2020; J. Chen et al. 2019) studied the microstructure and mechanical properties of L-PBF-processed 316L–C18400–Cu10Sn samples. The results showed that the bimetal tensile strength and elongation were between those of the two base metals. The microstructure of the cross-section of the bimetallic samples had element diffusion zones at the material interface, which aided in improving the bonding strength. It is noteworthy that these investigations found no brittle intermetallic phases formed in the parts manufactured by L-PBF. By contrast, microcracks were observed on the 316L side at the material interface (Figure 5-e and -f) but not on the copper alloy side. This is considered as a typical liquid metal embrittlement (LME) defect resulting from the loss of ductility and subsequent embrittlement of solid metals after coming into contact with a specific liquid metal. This phenomenon has been investigated in-depth in the study of welding dissimilar metals (Chen et al. 2013). The formation mechanism of the LME defect is elaborated in the section ‘Discussions and challenges in multi-material L-PBF’.
Critical Exploration of Liquid Metal Plasma-Facing Components in a Fusion Nuclear Science Facility
Published in Fusion Science and Technology, 2019
C. E. Kessel, D. Andruczyk, J. P. Blanchard, T. Bohm, A. Davis, K. Hollis, P. W. Humrickhouse, M. Hvasta, M. Jaworski, J. Jun, Y. Katoh, A. Khodak, J. Klein, E. Kolemen, G. Larsen, R. Majeski, B. J. Merrill, N. B. Morley, G. H. Neilson, B. Pint, M. E. Rensink, T. D. Rognlien, A. F. Rowcliffe, S. Smolentsev, M. S. Tillack, L. M. Waganer, G. M. Wallace, P. Wilson, S.-J. Yoon
A serious failure mode for LM and solid combinations is often called liquid metal embrittlement (LME) (or many other names). In this situation the LM can rapidly penetrate a solid and severely embrittle it, allowing rapid crack propagation in the solid when it is under tensile stress. Any LM-solid combination must be shown not to be susceptible to this mechanism before it can be accepted for application in a fusion reactor. This could be dependent on impurities in the LM as well as the solid. Although this mechanism has been recognized since the 1950s, it has obtained only an empirical understanding. Difficulties arise due to different mechanisms for embrittlement, different rates of embrittlement, and sensitivity to environmental conditions. There are well-known LME pairs such as Al-solid and Hg-liquid, stainless steel–solid and Zn-liquid, and steel-solid and Cu-liquid. There is a wide range of related processes including stress corrosion cracking, corrosion fatigue, and hydrogen embrittlement. There is an enormous body of literature on LME; some older references discuss observations and include Refs. 99 and 100, some attempt to coordinate observations,101 and some recent efforts can be found in Refs. 102 and 103 although these are hardly exhaustive. Attempts to develop predictive models have generally suffered from numerous counterexamples that can be found in the experimental literature. It is critical to develop a reliable and accessible experimental process for identifying susceptibility for a given application (which would include normal and off-normal operation parameters). For example, if an accident resulted in the spilling of the LM onto the vacuum vessel (VV), the LM-VV solid combination would also require clearing against LME (in addition to the PFC substrate solid material) and at a wide range of temperatures and stresses.