Numerical study of the stress state of a deformation twin in magnesium
TL;DR: In this paper, a numerical study of the distribution of the local stress state associated with deformation twinning in Mg is presented, both inside the twinned domain and in its immediate neighborhood, due to the accommodation of the twinning transformation shear.
About: This article is published in Acta Materialia.The article was published on 2015-02-01 and is currently open access. It has received 188 citations till now. The article focuses on the topics: Crystal twinning & Critical resolved shear stress.
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TL;DR: It is shown with a magnesium alloy containing 4 wt% lithium, that the same impressively large compression failure strains can be achieved with DTWs as without, rationalize that relatively easier slip characteristic of this alloy plastically relaxed the localized stress concentrations that DTWs can generate.
Abstract: Based on their high specific strength and stiffness, magnesium alloys are attractive for lightweight applications in aerospace and transportation, where weight saving is crucial for the reduction of carbon dioxide emissions. Unfortunately, the ductility of magnesium alloys is usually limited. It is thought that one reason for the lack of ductility is that the development of - double twins (DTW) cause premature failure of magnesium alloys. Here we show with a magnesium alloy containing 4 wt% lithium, that the same impressively large compression failure strains can be achieved with DTWs as without. The DTWs form stably across the microstructure and continuously throughout straining, forming three-dimensional intra-granular networks, a potential strengthening mechanism. We rationalize that relatively easier slip characteristic of this alloy plastically relaxed the localized stress concentrations that DTWs can generate. This result may provide key insight and an alternative perspective towards designing formable and strong magnesium alloys.
175 citations
TL;DR: In this article, a multi-level constitutive model for polycrystalline metals that deform by a combination of elasticity, slip and deformation twinning was developed, where the first level uses an upper bound Taylor-type crystal plasticity (T-CP) theory to relate the single-crystal scale to the polycrystal meso-scale and the second level employs an implicit finite elements (FE) approach to relate meso scale to macro-scale.
169 citations
TL;DR: It is shown that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin Transmission in hcp materials such as Mg, Zr and Ti.
Abstract: Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.
143 citations
TL;DR: In this article, the general topological model for interfacial defects is reviewed and expanded, and the role of these defects in the coupled shear migration of interfaces is explored, focusing on twinning in hexagonal metals for many defect examples.
140 citations
TL;DR: In this article, the effect of nearest neighboring grains on the propensity for twin growth in Mg and Zr was studied and it was shown that the neighboring grain constraint tends to oppose further growth and that the critical applied stress needed to overcome this resistance depends on neighboring grain orientation.
136 citations
References
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TL;DR: An alternate method based on Fourier series which avoids meshing and which makes direct use of microstructure images is proposed, based on the exact expression of the Green function of a linear elastic and homogeneous comparison material.
1,170 citations
TL;DR: In this article, the monotonic and cyclic mechanical behavior of O-temper AZ31B Mg sheet was measured in large-strain tension/compression and simple shear.
897 citations
TL;DR: In this paper, the role of the twins as barriers to dislocations is explicitly incorporated into the hardening description of slip deformation via a directional Hall-Petch mechanism.
537 citations
TL;DR: In this paper, an n-site formulation for elastic and viscoplastic anisotropic 3D polycrystals based on the Fast Fourier Transform (FFT) algorithm is presented.
449 citations
TL;DR: This paper conducted a statistical analysis on large data sets generated by electron backscattering diffraction (EBSD) to extract quantitative and meaningful relationships between material microstructure and deformation twinning in magnesium.
Abstract: To extract quantitative and meaningful relationships between material microstructure and deformation twinning in magnesium, we conduct a statistical analysis on large data sets generated by electron backscattering diffraction (EBSD). The analyses show that not all grains of similar orientation and grain size form twins, and twinning does not occur exclusively in grains with high twin Schmid factors or in the relatively large grains of the sample. The number of twins per twinned grain increases with grain area, but twin thickness and the fraction of grains with at least one visible twin are independent of grain area. On the other hand, an analysis of twin pairs joined at a boundary indicates that grain boundary misorientation angle strongly influences twin nucleation and growth. These results question the use of deterministic rules for twin nucleation and Hall–Petch laws for size effects on twinning. Instead, they encourage an examination of the defect structures of grain boundaries and their role in twin ...
444 citations