Effect of the Microstructure on the Fatigue Strength of a TiAl Intermetallic Alloy Produced by Additive Manufacturing
- PDF / 105,813,561 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 5 Downloads / 231 Views
Effect of the Microstructure on the Fatigue Strength of a TiAl Intermetallic Alloy Produced by Additive Manufacturing M. Filippini1, S. Beretta1, C. Içöz1 and L. Patriarca1,2 1
Politecnico di Milano, Dipartimento di Meccanica, Via La Masa 1, 20156 Milano, Italy. Dept. Mech. Science and Engng, University of Illinois at Urbana-Champaign, 1206 W. Green St., Urbana, IL 61801, U.S.A. 2
ABSTRACT In this work we examine a Ti-48Al-2Cr-2Nb alloy obtained with an additive manufacturing technique by Electron Beam Melting (EBM) by conducting monotonic and cyclic loading experiments both on tension and compression samples for investigating the influence of the microstructure in strain accumulation process by fatigue loading. The residual strain maps corresponding to different applied stress levels, number of cycles and microstructures are obtained through the use of high-resolution Digital Image Correlation (DIC). The strain maps were overlaid with the images of the microstructure and detailed analyses were performed to investigate the features of the microstructure where high local strain heterogeneities arise. Such experiments, conducted ex-situ at room temperature, allow to characterize the effect of different microstructures on the strain accumulation process, and to clearly identify the role of the microstructural features of this TiAl intermetallic alloy on the fatigue initiation process. INTRODUCTION Novel manufacturing process are more and more used to produce advanced structural materials as in the case of the gamma titanium aluminide intermetallic alloys (gamma-TiAl). The advantage of additive manufacturing, respect to other more conventional technologies for the production of components made of high performance materials, is to greatly reduce the high costs of tooling, allowing the designers to prove the fitness of new materials in much shorter time and at acceptable costs. In order to design mechanical components made of intermetallic γTiAl alloys produced with advanced manufacturing processes, a deep understanding of the damage accumulation process in the microstructure is required, for identifying suitable process parameters to obtain the required structural integrity of the components. In the last decade, more and more efforts have been devoted in understanding the effect of the local microstructure on the deformation of γ-TiAl alloys. Even though the investigations at the micro-scales provide useful information on the microscopic deformation mechanisms [1,2], there is the need to develop experimental tools for investigating the deformation behavior of these alloys at larger scales, which include several grains, still capturing the effect of the local microstructure. Using advanced optical techniques, in this work the origin of the strain heterogeneities in duplex γ-TiAl alloys are investigated by analyzing the strain fields originated from different microstructures (lamellar and equiaxed grains) for compressive and tensile cyclic loadings, by means of local strain field measurements via DIC technique [3], in co
