Ti-5Al-5V-5Mo-3Cr (Ti-5553) is recognized as a promising material for structural parts owing to the high hardenability and tailorable mechanical properties with heat treatment. Ti-5553 is a metastable beta titanium alloy available in both the wrought and powder form for additive manufacturing (AM). Beta titanium alloys offer an opportunity to increase hardenability, printability, strength, and damage tolerance versus the ubiquitous alpha-beta Ti-6Al-4V alloy. Wrought Ti-5553 is often used in the heat treated condition with a mixture of alpha and beta phases where it can obtain higher strength, hardenability, and fatigue resistance than the commonly used Ti-6Al-4V alloy. In contrast, when used in laser powder bed fusion, the Ti-5553 alloy solidifies in the beta phase due to the quick cooling rate, which improves printability and results in a part that can be subsequently hardened with heat treatment. While it is ideal to integrate all features into a single AM part, limitations in build
chamber size, design requirements, and other reasons can necessitate production of multiple parts with a secondary joining operation. Metal AM parts often have remaining porosity and non-isotropic properties due to the directional solidification, which can manifest differences in metallurgical features and mechanical behavior. In addition, the high sensitivity of thermal processing conditions on beta titanium alloy properties is a special consideration for subsequent welding operations.
In this study, keyhole laser welding using pulsed mode and continuous wave mode on Ti-5553 in the conventional wrought and additively manufactured (AM) conditions was completed and resulting metallurgical and mechanical properties were compared.
Optical microscopy and scanning electron microscopy (SEM) were used to characterize the microstructural constituents. Microhardness and tensile testing were used to assess mechanical properties. These results obtained from microstructural and mechanical characterization will be used to demonstrate the effect of processing on material behavior.
Sandia National Laboratories is a multimission laboratory managed and operated by
National Technology & Engineering Solutions of Sandia, LLC, a wholly owned
subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National
Nuclear Security Administration under contract DE-NA0003525.