Aiming to lower the cost and improve mechanical properties of AlCoCrFeNiTi x high-entropy alloys that were studied previously, the present research investigated the effect of removing Co and lowering Ti contents at various Al contents, namely Al x CrFeNiTi 0.25 . The microstructures were investigated using optical microscopy, scanning electron microscopy, energy disperse spectroscopy, x-ray diffraction and transmission electron microscopy. Compression tests were conducted at room temperature. The present study showed that with increasing Al contents, the phase structures of the alloys changed from FCC + BCC to double BCC as the main phases.Among the alloys studied, all of them exhibit distinguished workhardening especially the Al 0.5 CrFeNiTi 0.25 alloy has the highest fracture strength and plastic-strain limit of © 2014. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 3.47 GPa and 40 %, respectively with a yield strength of 1.88 GPa. The observed microstructure is analyzed using CALPHAD calculations.
The origins of the copper, tin and lead for China's rich Bronze Age cultures are a major topic in archaeological research, with significant contributions being made by archaeological fieldwork, archaeometallurgical investigations and geochemical considerations. Here, we investigate a recent claim that the greater part of the Shang-period metalwork was made using metals from Africa, imported together with the necessary know-how to produce tin bronze. A brief review of the current status of lead isotopic study on Shang-period bronze artefacts is provided first, clarifying a few key issues involved in this discussion. It is then shown that there is no archaeological or isotopic basis for bulk metal transfer between Africa and China during the Shang period, and that the copper and lead in Shang bronze with a strongly radiogenic signature is not likely to be from Africa. We call for collaborative interdisciplinary research to address the vexing question of the Shang period's metal sources, focusing on smelting sites in geologically defined potential source regions and casting workshops identified at a number of Shang settlements. KEYWORDS: LEAD ISOTOPES, HIGHLY RADIOGENIC LEAD, SHANG BRONZE, PROVENANCE INTRODUCTIONMost major Bronze Age civilizations developed in the catchments of large rivers that were sustaining a high population density through intensive agriculture. These areas, however, are almost always devoid of mineral resources, which are typically exposed only in mountainous areas, remote from the centres of agricultural civilization. Thus, these centres were dependent on distant areas to provide their strategically important metals, primarily copper, tin and gold, but also lead and silver. Substantive research has identified major copper sources for Egypt, Mesopotamia and Chen et al. 2009Chen et al. , 2016Pollard et al. 2017). Among these, Shang-period bronzes dated between the 16th and 11th centuries BCE stand out due to their highly distinctive isotopic and chemical compositions. The identification of the geological source(s) of this metal is a long-standing issue in Chinese archaeology, which has attracted considerable research interest from many scholars of various disciplinary backgrounds. A recent paper by Sun et al. (2016) is a new, but unconvincing, attempt to answer this question. It not only claims that 'the Yin-Shang people may have learned bronze technology elsewhere and brought it to China ' (Sun et al. 2016, 5), but it also concludes that 'both the Yin-Shang and the Sanxingdui bronzes were obtained in Africa, bearing the highly radiogenic lead isotopic signatures of Africa's Archean cratons. Alternatively, some ancient people might have come to China from Africa, carrying tin and/or bronzes with them' (Sun et al. 2016, 6). These hypotheses are undoubtedly bold and eye-catching, but unfortunately are also fundamentally flawed. In this paper, we offer a brief summary of currently available research on highly radiogenic lead found in ancient Shang bronzes, clarifying a few key issues that were m...
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