PM Manufacturing Research Boosted by Continuous Sintering Furnace

University of Missouri-Rolla has recently acquired a Fluidtherm laboratory continuous sintering furnace. Custom designed and built for PM research, the furnace will allow current efforts in sintering development, pressure gas quenching of PM steels, optimisation of toughness and fatigue properties of PM parts, and production of metal matrix composites to be enhanced and extended

Elevated Temperature Microstructure Stability of SLM 304L Stainless Steel

At elevated temperatures changes in metallurgical structure can be expected for almost any steel or alloy. In stainless steels, the changes can be grain growth, carbide precipitation, ferrite decomposition, or embrittlement. These phenomena can significantly affect the properties of the stainless steel and would potentially change the functionality of the component. Therefore, the impact of elevated temperatures on the microstructure of SLM 304L stainless steel was studied. The work reported here investigates the influence of different aging times at 300C on microstructure and mechanical properties of stainless steels (304L) fabricated with the Selective Laser Melting (SLM) process. Microstructure and mechanical properties were dramatically effected at temperatures much lower than expected when compared to samples of wrought stainless steel. The stainless steel fabricated using the SLM process was more kinetically active than expected based on previous studies of 304L. Results of this study will be presented along with possible reasons for the higher activity.Mechanical Engineerin

Mechanical Properties of Heusler Alloys

Heusler alloys have been a significant topic of research due to their unique electronic structure, which exhibits half-metallicity, and a wide variety of properties such as magneto-calorics, thermoelectrics, and magnetic shape memory effects. As the maturity of these materials grows and commercial applications become more near-term, the mechanical properties of these materials become an important factor to both their processing as well as their final use. Very few studies have experimentally investigated mechanical properties, but those that exist are reviewed within the context of their magnetic performance and application space with specific focus on elastic properties, hardness and strength, and fracture toughness and ductility. A significant portion of research in Heusler alloys are theoretical in nature and many attempt to provide a basic view of elastic properties and distinguish between expectations of ductile or brittle behavior. While the ease of generating data through atomistic methods provides an opportunity for wide reaching comparison of various conceptual alloys, the lack of experimental validation may be leading to incorrect conclusions regarding their mechanical behavior. The observed disconnect between the few available experimental results and the numerous modeling results highlights the need for more experimental work in this area

Optimization and Characterization of Novel Injection Molding Process for Metal Matrix Syntactic Foams

Metal matrix syntactic foams are particulate composites comprised of hollow or porous particles embedded in a metal matrix. These composites are difficult to manufacture due primarily to the lightweight, relatively fragile filler material. In this work, an injection molding process was developed for metal matrix syntactic foams. First, an aqueous binder was optimized for low-pressure injection molding. A mixture model was used to optimize the composition of the binder to achieve the highest relative density. The model predicted the maximum relative density was at a binder composition (in vol.%) of 7% agar, 4% glycerin, and 89% water. Second, this binder was used to manufacture copper matrix syntactic foams with 0, 5, 10, and 15 vol.% porous silica as the filler material. The solids loading for these compositions decreased with increasing filler material from 55 to 44 vol.%, likely due to binder filling the pores in the porous silica particles. Finally, the sample quality after injection molding was characterized. Only 0.11 ± 0.06 vol.% carbon remained in the samples. Silica particles were well-dispersed in the samples after sintering, and they did not appear to be fractured. The specific strength of the copper matrix material increased with increasing porous silica additions

Grain Size Effects in Selective Laser Melted Fe-Co-2V

The material science of additive manufacturing (AM) has become a significant topic due to the unique way in which the material and geometry are created simultaneously. Major areas of research within inorganic materials include traditional structural materials, shape memory alloys, amorphous materials, and some new work in intermetallics. The unique thermal profiles created during selective laser melting (SLM) may provide new opportunities for processing intermetallics to improve mechanical and magnetic performance. A parameter set for the production of Fe-Co-2V material with additive manufacturing is developed and efforts are made to compare the traditional wrought alloy to the AM version of the same chemistry. Evaluation includes magnetic properties, composition, and phase as a function of thermal history, as well as mechanical performance. Results show significant similarities in microstructure between AM and wrought materials, as well as mechanical and magnetic performance. Property trends are evaluated as a function of grain size and show effects similar to the Hall-Petch strengthening observed in wrought material, though with some underprediction of the strength. Magnetic properties qualitatively follow the expected trends but demonstrate some deviation from wrought material, which is still unexplained

Corrosion Resistant Nickel-Based Alloy

A nickel based, high silicon alloy exhibits very high corrosion resistance in high temperature sulfuric acid environments. The alloy may be cast and is sufficiently ductile to be fabricated and machined. The alloy is ductile and has sufficient resistance to mechanical and thermal shock to be reliable in service when used as rotating parts

Compositional Modifications to Alter and Suppress Laves Phases in AlxCrMoTayTi Alloys

Herein, the Development of Refractory Complex Concentrated Alloys in the Al–Cr–Mo–Ta–Ti Alloy System is Reported. Alloys with Modified Al and Ta Concentrations Are Designed using CALPHAD Tools and Produced Via Arc Melting and Characterized in Both As-Cast and Annealed Forms. Properties of the Alloys, Nature of the Microstructures, and Phase Transformation Behavior Are Described Via X-Ray Diffraction, Microstructural Characterization, Microhardness, and Differential Scanning Calorimetry. Two Alloys, Namely, Al0.25CrMoTa0.8Ti and Al0.75CrMoTa0.8Ti, Are Represented by a Body-Centered-Cubic Matrix Phase after Annealing, along with a Secondary Cr–Ta Laves Phase of the C15 and C14 Polytypes, respectively. in As-Cast and Annealed Forms, the Al0.75CrMoTa0.45Ti Alloy Comprises a Single-Bcc Phase. Microhardness of the Laves Phase Containing Alloys Demonstrates Susceptibility to Cracking, Whereas the Al0.75CrMoTa0.45Ti Alloy Displays High Specific Hardness, Signs of Ductility as Evidenced by Slip Traces Near Indentations, and Minimal Scatter of Hardness Values

Fundamental Effects of Al and Ta on Microstructure and Phase Transformations in the Al–cr–mo–ta–ti Refractory Complex Concentrated Alloy System

The effect of aluminum and tantalum concentrations on a refractory metal complex concentrated alloy is reported, particularly with respect to their effect on microstructure and phase composition of the alloy in cast and annealed form. Alloys with an equiatomic composition, (AlCrMoTaTi), an aluminum-lean composition (Al0.75CrMoTaTi), and a tantalum-lean composition (AlCrMoTa0.75Ti) are produced via arc melting. The alloys exhibit multiphase structures, confirmed by X-ray diffraction, microstructural characterization, and thermal analysis. The minor off-equiatomic adjustments of aluminum and tantalum in this alloy system did not drastically alter the prevalence of the Cr–Ta-based Laves phase. Correlations between thermodynamic predictions and observed phase transformations via thermal analysis are improved upon refinement of calculations removing impractical intermediate phases. Experimental findings provide information for the refinement of thermodynamic modeling and deliver additional insight into the optimization of alloy compositions within this five-component system

Evaluation of Mechanical Properties and Microstructure for Laser Deposition Process and Welding Process

Laser Aided Manufacturing Process (LAMP) can be applied to repair steel die/molds which are currently repaired using traditional welding process in industry. In order to fully understand the advantages of laser deposition repair process over traditional welded-repair process, the mechanical properties such as tensile strength and hardness of H13 tool steel samples produced by these two processes were investigated. The microstructure and fracture surface of the samples were analyzed using optical microscope and SEM (Scanning Electron Microscope). Moreover, depositions on substrates with different shapes were studied to evaluate the performance of LAMP on damaged parts with complicated geometric shape.Mechanical Engineerin

Progress in Effect of Jominy End Quench on the Microstructure and Mechanical Properties of Cast Aluminum Alloys

In this review, the current knowledge related to the relationship between the heat treatment process and the microstructure and mechanical properties of A356 aluminum alloys are summarized. The review also examines the use of the Jominy end quench (JEQ) specimen and its application to the examination of the effects of quench rate and subsequent processing. Using the design of experimental methods combined with the Jominy end quench technique, desired changes in microstructure and mechanical properties of alloys can be obtained. So, the experimental technique of the Jominy end quench was concerned in this work