Doctor of Philosophy, The Ohio State University, 2008, Materials Science and Engineering

The beneficial influence of boron additions on processing, microstructure, physical and mechanical properties of various titanium alloys has been recognized since 1950's. However, boron additions to titanium alloys to obtain specific microstructures and mechanical properties for several niche applications, including automotive and aerospace, have been actively studied during the past 25 years. The addition of boron concentrations greater than 0.05 wt.% to titanium alloys creates a dispersion of TiB. The presence of TiB enhances the tensile and fatigue strengths as well as the wear resistance as compared to the original titanium alloy. Although these improvements in mechanical properties are attractive, there are still two major obstacles in using these alloys: (1) relationship of microstructure and mechanical properties in Ti-B alloys needs further investigation to optimize the alloys for specific commercial applications; and (2) cost to benefit ratio of producing these alloys is high for a given application(s). The Armstrong process is a novel process that can produce commercially pure (CP) titanium and titanium alloy powder directly from TiCl4 (and other metal halides or as required, to obtain the desired alloy composition). The Armstrong process uses sodium as a reducing agent, with similar reactions as the Hunter process using sodium as a reducing agent and Kroll process using magnesium as a reducing agent. The Armstrong process forms CP-Ti and titanium alloyed powder, which can be directly consolidated or melted into the final product. In comparing the downstream processing steps required by the Kroll and Hunter processes with direct consolidation of Armstrong powder, several processing features or steps are eliminated: (1) restriction of batch processing of material, (2) blending of titanium sponge and master alloy material to create titanium alloys, (3) crushing of the sponge product, (4) melting, and (5) several handling steps. The main objective of this res (open full item for complete abstract)

Committee: James Williams (Advisor) Subjects: Textile Technology

Master of Science in Engineering, University of Akron, 2010, Civil Engineering

Rapid industrial growth and advances in the domains of engineering and related technologies during the last fifty years have led to the extensive use of traditional metals and their alloy counterparts. Titanium is one such metal which has gained wide popularity in the aerospace and defense related applications owing to a wide range of impressive mechanical properties like excellent specific strength (σUTS/ρ), stiffness, corrosion and erosion resistance, fracture toughness and capability to withstand significant temperature variations. Two materials, namely commercial purity titanium (Grade 2), referred to henceforth as Ti- CP (Grade 2) and the “work-horse” alloy Ti-6Al-4V have been chosen for this research study. The intrinsic influence of material composition and test specimen orientation on the tensile and fatigue behavior for both Ti- CP (Grade 2) and Ti-6Al-4V have been discussed. Samples of both Ti- CP (Grade 2) and Ti-6Al-4V were prepared from the as-provided plate stock along both the longitudinal and transverse orientations. The specimens were then deformed to failure in uniaxial tension for the tensile tests and cyclically deformed at different values of maximum stress at constant load ratio of 0.1 for the high cycle fatigue tests. The microstructure, tensile properties, resultant fracture behavior of the two materials is presented in the light of results obtained from the uniaxial tensile tests. The conjoint influence of intrinsic microstructural features, nature of loading and specimen properties on the tensile properties is discussed. Also, the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of applied stress-microstructural feature interactions in governing failure for the cyclic fatigue properties for both the materials under study Ti- CP (Grade 2) and the “work-horse” alloy Ti-6Al-4V have been discussed in detail. Careful study of the microstructure for Ti-CP (Grade 2) material at a low magnification re (open full item for complete abstract)

Committee: Anil Patnaik Dr. (Advisor) Subjects: Civil Engineering; Materials Science

Master of Science, University of Akron, 2010, Civil Engineering

Titanium is well recognized as a modern and high performance metal that is much stronger and lighter than the most widely used steels in the industry. There is a growing need to reduce the part weight, cost and lead time, while concurrently facilitating enhanced performance of structural parts made from titanium and titanium alloys. Structural components made from titanium have the advantage of high strength-to-weight ratio, and high stiffness-to-weight ratio. Owing to good resistance to corrosion and superior ballistic properties, titanium is used in several defense applications. This thesis presents a summary of the research conducted on welded built-up titanium beams so as to eventually facilitate the design, fabrication, and implementation of titanium in large structural members. An alternative to machining a structural component from thick plates or billets is to fabricate beams using the built-up concept. Rolled plates and sheets of titanium alloys can be cut to size and welded together to fabricate a built-up structural component. The primary objective of this project is to investigate structural performance of built-up welded beams fabricated from commercially pure (Grade 2) titanium and a common alloy (Ti-6Al-4V) under both static and fatigue loading conditions. Six welded built-up titanium beams were fabricated and tested to experimentally and theoretically evaluate structural performance. Analysis and design approaches for static and fatigue performance of built-up beams were also studied and it is clearly demonstrated that it is feasible to fabricate large built-up titanium beams by welding parts together using GMAW-P welding process. The welds produced by this method were found to be sound and without any visible cracks. The study also revealed that there is no deleterious influence of welding on structural performance of the built-up welded beams of commercially pure titanium and Ti-6Al-4V titanium alloy. With suitable modifications to the current AISC (open full item for complete abstract)

Committee: Anil Patnaik Dr (Advisor); Tirumalai Srivatsan Dr. (Advisor); Dr. Craig Menzemer PhD (Committee Member) Subjects: Civil Engineering

Master of Science, The Ohio State University, 2012, Industrial and Systems Engineering

The design of lightweight sheet metal part components requires an understanding of material characteristics and their manufacturing processes. Increasing use of Advance High Strength Steels (AHSS) and Commercially Pure (CP) titanium sheets accompanied by many challenges due to their unique mechanical properties and low formability. Thus, developing fundamental understanding of mechanical properties is critical for successful process and tool design. FE simulations are powerful tool in identification of challenges in forming of these materials and product realization. Therefore, FE model inputs, including flow stress data, play important role for obtaining accurate results. However, obtaining the flow stress curve near production conditions (state of stress strain) might be challenging and requires material characterization test that emulates near production conditions. In this study, uniaxial tensile and biaxial Viscous Pressure Bulge (VPB) tests were conducted at room temperature to obtained material properties and flow stress for sheet materials: • DP780 (AHSS) (Thickness= 1 mm) • CP-Ti (Grade: 2) = Material A (Thickness = 1.8 mm and heat lot = HT 884971-02-00) • CP-Ti (Grade: 2) = Material B (Thickness = 0.5 mm and heat lot= KX16EM) • CP-Ti = Material C (Thickness = 1 mm and heat lot = W58KEM) Flow stresses obtained from tensile and VPB tests were compared. The strain ratios (R-values) were determined by conducting tensile tests and they were used to correct flow stress curves that obtained from VPB test for anisotropy. In VPB test, it is obvious that flow stress data can be obtained to higher strain values compared to tensile tests. Therefore, the state of stress strain from VPB test emulates real sheet metal forming conditions where process is almost always biaxial. The objective of this study was to predict springback angles in air bending process by using flow stress curves that obtained from both tensile and VPB tests. Air bending process was successfully (open full item for complete abstract)

Committee: Taylan Altan Dr. (Advisor); Jerald Brevick Dr. (Committee Member); Prasad Mokashi Dr. (Committee Member) Subjects: Industrial Engineering