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首页> 外文期刊>Materials Science and Engineering >Controlling martensitic decomposition during selective laser melting to achieve best ductility in high strength Ti-6Al-4V
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Controlling martensitic decomposition during selective laser melting to achieve best ductility in high strength Ti-6Al-4V

机译：在选择性激光熔化过程中控制马氏体分解，以在高强度Ti-6Al-4V中获得最佳延展性

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摘要

Systematic variations of the exposure time and point distance of the pulsed laser used in selective laser melting (SLM) of Ti-6Al-4V resulted in three representative microstructures: the fully martensitic alpha', the near-alpha' containing a small amount of isolated beta, and the fully lamellar alpha/beta. The energy density in SLM determines the steady-state temperature in a deposited layer reached by balance between heat input from the subsequent layers and heat loss into the previous ones. A critical energy density was revealed below which no in-situ alpha' decomposition occurred. On the other hand, the in-situ formation of fully lamellar alpha/beta was obtained using energy density higher than this critical value, leading to a steady-state temperature above that for alpha' decomposition for a sufficiently long duration. All three microstructures exhibited high tensile yield strength of 1100-1150 MPa, with excellent tensile elongation in the fully martensitic alpha' (similar to 15%) and fully lamellar alpha/beta (similar to 12%) but significantly lower ductility in the near-alpha' ( 6%). The best ductility observed in the fully martensitic alloy dismisses the myth that alpha' is inherently brittle. Instead, the brittleness in the near-alpha' alloy can be attributed to the presence of thin beta lamellae on the primary alpha' plates oriented at similar to 45 degrees to the tensile axis, causing substantial stress concentration at the alpha/beta interface.
机译：Ti-6Al-4V的选择性激光熔化（SLM）中使用的脉冲激光的曝光时间和点距的系统变化产生了三个代表性的微观结构：完全马氏体的α'，包含少量隔离物的近α' beta和完全层状的alpha / beta。 SLM中的能量密度决定了沉积层中的稳态温度，该温度是由后续层输入的热量与进入先前层的热量损失之间达到平衡所达到的。揭示了临界能量密度，在该临界能量密度以下没有发生原位α'分解。另一方面，使用高于该临界值的能量密度获得了完全层状α/β的原位形成，从而在足够长的时间内导致稳态温度高于α'分解的稳态温度。这三种微观结构均表现出1100-1150 MPa的高拉伸屈服强度，在完全马氏体α'（约15％）和完全层状α/β（约12％）中具有出色的拉伸伸长率，但在近- alpha'（<6％）。在全马氏体合金中观察到的最佳延展性消除了α'固有脆性的神话。取而代之的是，近α'合金的脆性可归因于在与拉伸轴成45度角的方向上取向的初次α'板上存在薄的β薄片，从而在α/β界面处引起大量应力集中。

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