The vertical and triangular morphology in the as-deposited Ti-6Al-4V

Haozhang Zhong, Liu ZY, Jianfeng Gu

Keywords:Vertical morphology;Triangular morphology;Self-accommodation;Misorientation

Abstract:The martensite plates in the metal alloys form the special morphologies, such as the triangular, spike, diamond and butterfly morphologies. The Ti-6Al-4V processed by laser melted deposition shows the fine martensite in the prior columnar beta grains. No relevant report has shed light on the specific morphology of the martensite plate group. The current work reveals that the martensite plates cluster as the vertical and the triangular morphologies. The vertical morphology is readily observed by optical microscope and transmission electron microscope. Whereas the triangular morphology is solely characterized in the transformation electron microscope. It reveals that the martensite plates in the triangular morphology are finer than that in the vertical morphology. Besides, the triangular and vertical morphology are related to the misorientations 60° or 90° or so. The misorientation distribution indicates the proportion of these morphologies to some degree. Thus the microstructure model, including the information of the size and the proportion of these morphologies, is appropriately proposed. Noting that the thermal cycles happen in laser melted deposition, it is concluded that the vertical morphology forms as the primary martensite and the triangular morphology forms as the secondary martensite.