Microstructure evolution and mechanical properties of multi-layer deposition of Ti-6Al-4V-5Ni alloy developed by μ-plasma-based metal additive manufacturing process

Abstract

This manuscript describes the study of density, porosity, microstructure, formation of phases, elemental distribution, tensile properties, fractography, microhardness, fracture toughness, and abrasion resistance of multi-layer deposition Ti-6Al-4V-5Ni alloy developed by μ-plasma metal additive manufacturing (μ-PBMAM) process for high temperature and high strength applications. It also presents comparison of these aspects with multi-layer depositions of Ti-6Al-4V alloy. Thermo-calc simulated phase diagram was used to decide at.% of Ni to be added to aerospace grade Ti-6Al-4V alloy. It found that adding 5% of Ni promotes grain refinement without forming C14 Laves phase and increasing the β-transus temperature. Optimum values of μ-plasma power and μ-plasma torch travel speed were identified by manufacturing single-layer depositions of Ti-6Al-4V-5Ni alloy thorough diluted depth, aspect ratio, deposition quality, deposition geometry, and deposition efficiency as the criteria to manufacture its multi-layer deposition. Results reveal that inclusion of nickel to Ti-6Al-4V alloy increased the volumetric percentage of β-Ti phase from 13 to 27% and refined grains of α-Ti and β-Ti phases which improved yield and ultimate tensile strength of Ti-6Al-4V-5Ni alloy by 13.4% and 17.8% respectively and reduced % elongation by 36% as compared to Ti-6Al-4V alloy. It changed fractured pattern from ductile to combined ductile and brittle fracture consisting of cleavage facets, voids, and larger size dimples. It increased % porosity, microhardness, fracture toughness, and abrasion resistance thus imparting Ti-6Al-4V-5Ni alloy more resistance to crack initiation and more restriction to movement of the dislocations. Vanadium and nickel contents in β-Ti phase of Ti-6Al-4V-5Ni alloy are 3 to 5 times and 21 to 25 times more than that its α-Ti phase, respectively. Findings of this work demonstrate that μ-PBMAM developed Ti-6Al-4V-5Ni alloy is useful for high temperature, high strength, and light weight applications in aerospace, space, automobile, and dies and mold industries due to promotion and grain refinement of β-Ti phase, improvement in microstructure, microhardness, yield and tensile strength, fracture toughness, abrasion resistance. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.