Effect of Laser Energy Density, Internal Porosity and Heat Treatment on Mechanical Behavior of Biomedical Ti6Al4V Alloy Obtained with DMLS Technology

Żaneta Anna Mierzejewska

Abstract

The purpose of this paper was to determine the influence of selected parameters of Direct Metal Laser Sintering and various heat treatment temperatures on the mechanical properties of Ti6Al4V samples oriented vertically (V, ZX) and horizontally (H, XZ). The performed micro-CT scans of as-build samples revealed that the change in laser energy density significantly influences the change in porosity of the material, which the parameters (130–210 W; 300–1300 mm/s), from 9.31% (130 W, 1300 mm/s) to 0.16% (190 W, 500 mm/s) are given. The mechanical properties, ultimate tensile strength (UTS, Rm) and yield strength (YS, Re) of the DMLS as-build samples, were higher than the ASTM F 1472 standard suggestion (UTS = 1100.13 ± 126.17 MPa, YS = 1065.46 ± 127.91 MPa), and simultaneously, the elongation at break was lower than required for biomedical implants (A = 4.23 ± 1.24%). The low ductility and high UTS were caused by a specific microstructure made of α’ martensite and columnar prior β grains. X-Ray Diffraction (XRD) analysis revealed that heat treatment at 850 °C for 2 h caused the change of the microstructure intothe α + β combination, affecting the change of strength parameters—a reduction of UTS and YS with the simultaneous increase in elongation (A). Thus, properties similar to those indicated by the standard were obtained (UTS = 908.63 ± 119.49 MPa, YS = 795.9 ± 159.32 MPa, A = 8.72 ± 2.51%), while the porosity remained almost unchanged. Moreover, the heat treatment at 850 °C resulted in the disappearance of anisotropic material properties caused by the layered structure (UTSZX = 908.36 ± 122.79 MPa, UTSXZ = 908.97 ± 118.198 MPa, YSZX = 807.83 ± 124.05 MPa, YSXZ = 810.56 ± 124.05 MPa, AZX = 8.75 ± 2.65%, and AXZ = 8.68 ± 2.41%).
Author Żaneta Anna Mierzejewska (FME / DBBE)
Żaneta Anna Mierzejewska,,
- Department of Biocybernetics and Biomedical Engineering
Journal seriesMaterials, ISSN 1996-1944, (N/A 140 pkt)
Issue year2019
Vol12
No14
Pages1-23
Publication size in sheets1.1
Keywords in EnglishSelective Laser Melting, Direct Metal Laser Sintering, porosity, titanium alloys, yield strength, ultimate tensile strength, X-Ray Diffraction
ASJC Classification2500 General Materials Science
DOIDOI:10.3390/ma12142331
URL https://www.mdpi.com/1996-1944/12/14/2331
Internal identifierROC 19-20
Languageen angielski
LicenseJournal (articles only); published final; Uznanie Autorstwa (CC-BY); with publication
Score (nominal)140
Score sourcejournalList
ScoreMinisterial score = 140.0, 12-02-2020, ArticleFromJournal
Publication indicators Scopus SNIP (Source Normalised Impact per Paper): 2017 = 1.285; WoS Impact Factor: 2018 = 2.972 (2) - 2018=3.532 (5)
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