Additively manufactured Nb-Ti-Si based alloy: As-built and heat-treated conditions

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters Pub Date : 2024-09-17 DOI:10.1016/j.addlet.2024.100242

Runqi Gao , Hui Peng , Hongbo Guo , Bo Chen

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Abstract

This work aims to fully characterise the Nb-Ti-Si based alloy (Nb-26Ti-16Si-2.2Al-2Cr), processed by the electron-beam powder-bed-fusion in both as-built and heat-treated conditions, to elucidate the microstructure-property relationships. The as-built condition has [001]-oriented columnar grains of the Nb₃Si phase with the Nbss phase dispersed throughout the microstructure. The microhardness is 645.2 ± 6.7 HV_0.5, and the indentation fracture toughness shows distinct directionality: 7.7 MPa·m^1/2 in the horizontal direction compared to 5.3 MPa·m^1/2 in the vertical direction. Both properties are comparable to the cast version. The directionality is attributed to the underlying mechanisms such as crack bridging, arrest, and micro-crack formation. By contrast, in the heat-treated condition, the alloy exhibits a dual-phase microstructure (Nbss and Nb₅Si₃ phases) with near-equiaxed grain shape due to the Nb₃Si phase decomposition. The fracture toughness increases to 12.1 MPa·m^1/2, at the expense of a reduced microhardness of 564.4 ± 15.0 HV_0.5.

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以铌钛硅为基础的添加式制造合金：坯料和热处理条件

本研究旨在全面描述通过电子束粉末床熔融技术加工的铌钛硅基合金（Nb-26Ti-16Si-2.2Al-2Cr）在坯料和热处理两种条件下的特性，以阐明其微观结构与性能之间的关系。在坯料状态下，Nb3Si 相具有[001]取向的柱状晶粒，Nbss 相分散在整个微观结构中。显微硬度为 645.2 ± 6.7 HV0.5，压痕断裂韧性具有明显的方向性：水平方向为 7.7 MPa-m1/2，垂直方向为 5.3 MPa-m1/2。这两项性能都与铸件相当。这种方向性归因于裂纹桥接、停滞和微裂纹形成等基本机制。相比之下，在热处理状态下，由于 Nb3Si 相分解，合金呈现出双相微观结构（Nbss 和 Nb5Si3 相），晶粒形状接近等轴。断裂韧性增加到 12.1 MPa-m1/2，但显微硬度却降低到 564.4 ± 15.0 HV0.5。

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