As there are still issues with Webex, this defense will be held on Zoom instead. Here is the new link:
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Hello ME Community,You are invited to join (online) the PhD Dissertation Defense of Julianna Posey, on Wednesday, April 16, 2025, beginning at 9:00am ET.
https://umbc.webex.com/meet/jposey1
Advisor: Marc Zupan
Title: Characterization of Conventionally and Additively Manufactured 17-4 PH Stainless Steel Hybrid Welded Joints
Abstract:
Metal additive manufacturing (AM) is a revolutionary technology that enables the on-demand production of in tri cate components directly from digital models. In laser beam metal powder bed fusion (PBF /LB-M), AM parts are built by melting metal powder in a layer-by-layer process, offering a fast, efficient manufacturing route. This method supports industries seeking economic and sustainable solutions by enabling a low buy-to-fly ratio. The strategic benefits of AM have created a significant demand for research into the microstructure-property-performance relationships of various materials and applications. The 17% Chromium - 4% Nickel precipitation hardening (17-4 PH) alloy is a martensitic stainless steel selected for study due to its superb strength, ductility, and corrosion resistance. Current studies indicate that a two-step precipitation hardening heat treatment of 17-4 PH material produced via AM can achieve tensile properties comparable to, or exceeding, those of fully strengthened conventionally manufactured 17-4 PH material. Although the material and mechanical properties of AM 17-4 PH steel have been extensively studied as standalone components, the impact of high temperature joining operations, such as gas tungsten are welding (GTAW), on this AM alloy have not been addressed in present literature. While post-welding heat treatments are typically favorable for the 17-4 PH alloy, anticipated applications for AM components may limit or prevent heat treatment after installation.
In this work, AM 17-4 PH steel is subjected to thermal processes (solutionizing and aging to three different conditions) to evaluate its material and mechanical properties compared to those of conventionally manufactured 17-4 PH steel. With an appropriate understanding of how heat treatments affect the AM alloy, the material is subsequently welded in both conventional-to-conventional and hybrid AM-to-conventional configurations. This research characterizes the weldability of the fully hardened material and compares its material and mechanical behavior in these configurations.
Transversa tensile and fatigue testing, along with essential microstructural analysis, demonstrates that additive material can be successfully welded to conventional material of matching strength conditions in both autogenous and homogeneous configurations. However, the faster diffusion rate of the additive base material appears to weaken the heat affected zone, resulting in reduced ductility and strength in hybrid
AM-to-conventional welds compared to fully conventionally manufactured welds. The primary contribution of this research is the connection established between the microstructural evolution of the AM 17-4 PH alloy and the properties of its transversa welds. This underscores the importance of characterizing the
microstructure-property-performance relationships in additively manufactured alloys for diverse applications.
Advisor: Marc Zupan
Title: Characterization of Conventionally and Additively Manufactured 17-4 PH Stainless Steel Hybrid Welded Joints
Abstract:
Metal additive manufacturing (AM) is a revolutionary technology that enables the on-demand production of in tri cate components directly from digital models. In laser beam metal powder bed fusion (PBF /LB-M), AM parts are built by melting metal powder in a layer-by-layer process, offering a fast, efficient manufacturing route. This method supports industries seeking economic and sustainable solutions by enabling a low buy-to-fly ratio. The strategic benefits of AM have created a significant demand for research into the microstructure-property-performance relationships of various materials and applications. The 17% Chromium - 4% Nickel precipitation hardening (17-4 PH) alloy is a martensitic stainless steel selected for study due to its superb strength, ductility, and corrosion resistance. Current studies indicate that a two-step precipitation hardening heat treatment of 17-4 PH material produced via AM can achieve tensile properties comparable to, or exceeding, those of fully strengthened conventionally manufactured 17-4 PH material. Although the material and mechanical properties of AM 17-4 PH steel have been extensively studied as standalone components, the impact of high temperature joining operations, such as gas tungsten are welding (GTAW), on this AM alloy have not been addressed in present literature. While post-welding heat treatments are typically favorable for the 17-4 PH alloy, anticipated applications for AM components may limit or prevent heat treatment after installation.
In this work, AM 17-4 PH steel is subjected to thermal processes (solutionizing and aging to three different conditions) to evaluate its material and mechanical properties compared to those of conventionally manufactured 17-4 PH steel. With an appropriate understanding of how heat treatments affect the AM alloy, the material is subsequently welded in both conventional-to-conventional and hybrid AM-to-conventional configurations. This research characterizes the weldability of the fully hardened material and compares its material and mechanical behavior in these configurations.
Transversa tensile and fatigue testing, along with essential microstructural analysis, demonstrates that additive material can be successfully welded to conventional material of matching strength conditions in both autogenous and homogeneous configurations. However, the faster diffusion rate of the additive base material appears to weaken the heat affected zone, resulting in reduced ductility and strength in hybrid
AM-to-conventional welds compared to fully conventionally manufactured welds. The primary contribution of this research is the connection established between the microstructural evolution of the AM 17-4 PH alloy and the properties of its transversa welds. This underscores the importance of characterizing the
microstructure-property-performance relationships in additively manufactured alloys for diverse applications.