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Articles 1 - 30 of 89
Full-Text Articles in Metallurgy
Metallurgical Impact Of Switching From Hammer Units To Hydraulic Presses For Forging, Cole Hawker, Jacob Reed
Metallurgical Impact Of Switching From Hammer Units To Hydraulic Presses For Forging, Cole Hawker, Jacob Reed
Materials Engineering
Carlton Forge Works (CFW) is evaluating the retirement of its hammer units in favor of hydraulic presses to address safety concerns in forging aerospace components. This paper investigates the metallurgical implications of this transition, emphasizing the importance of superior microstructures and meeting industry standards and customer requirements. The alloys in question are Titanium-6Al-4V (Ti64) and Inconel 718 (INCO 718), which comprise a majority of CFW’s production. Ti64's high specific strength and thermal stability make it ideal for aerospace applications, while INCO 718 is recognized for superior high-temperature creep performance. Defects like freckles and white spots in INCO 718 are analyzed …
Improving The Tensile Mechanical Properties Of Direct Energy Deposited (Ded) Inconel 718 Aircraft Components Using A Standard Heat Treatment, Spencer Vincent Flynn
Improving The Tensile Mechanical Properties Of Direct Energy Deposited (Ded) Inconel 718 Aircraft Components Using A Standard Heat Treatment, Spencer Vincent Flynn
Materials Engineering
This project aimed to improve the mechanical properties of as-printed additively manufactured Inconel 718 samples using a heat treatment usually used for cast and wrought Inconel 718. The mechanical properties sought to be optimized were yield strength, ultimate tensile strength, elongation, and reduction in area. The property goals were to match or exceed those of cast and heat treated Inconel 718. Wire-fed electron beam direct energy deposition (DED) was used to manufacture the samples, which were then heat treated using the AMS 5663 standard in an inert atmosphere. The samples were then tested in tension to obtain data on their …
Failure Analysis Of Variably Sized 4340 Steel Mandrels Utilized In The Production Of Seamless Superalloy Rings Through The Vertical Ring Rolling Process, Mikhail Alexeyevich Vasilyev, Joshua Brady Venz
Failure Analysis Of Variably Sized 4340 Steel Mandrels Utilized In The Production Of Seamless Superalloy Rings Through The Vertical Ring Rolling Process, Mikhail Alexeyevich Vasilyev, Joshua Brady Venz
Materials Engineering
Vertical ring rolling is a forging process which forms seamless metal rings through applying a large force at elevated temperatures onto component materials stabilized by cylindrical mandrels. Carlton Forge Works, a company which produces rings of superalloy materials such as INCO718 and 718Plus, is experiencing a consistent failure of mandrels due to extreme conditions. An analysis of the lifetime (bulk material, heat treatment, and use) was performed, which aided in the identification of process variables tied to mandrel failure. Experiments were formed surrounding three variables of the mandrel heat treatment: Austenitization temperature, quenching temperature, and tempering conditions, with the goal …
Investigation Into Oxygen Diffusion As It Relates To Alpha Case Formation In Ti-6al-4v Based On Different Forging Thermal Cycles, Tyler J. Meador, Jon Leduc, Francesca Hope
Investigation Into Oxygen Diffusion As It Relates To Alpha Case Formation In Ti-6al-4v Based On Different Forging Thermal Cycles, Tyler J. Meador, Jon Leduc, Francesca Hope
Materials Engineering
An investigation into the growth kinetics of alpha case in Ti-6Al-4V in the presence of oxygen was conducted for different forging thermal cycles. This was done to determine whether the alpha case should be removed after each thermal cycle or as the final step after forging. The thermal cycles consisted of four hours at 1750 °F. Samples were subjected to this treatment one, two, three, and four times along with a continuous sixteen hour hold. Four cycle and Hold samples were subjected to an additional thermal cycle above the beta transus at 1925 °F. These then went through a final …
Analysis Of Novel Corrosion Resistant Maraging Steels For Use In Additive Manufacturing, Bradley Michael Samuel, James Knowlton Smith
Analysis Of Novel Corrosion Resistant Maraging Steels For Use In Additive Manufacturing, Bradley Michael Samuel, James Knowlton Smith
Materials Engineering
Stainless maraging steel has been proven to be an industry standard material for plastic injection molds. Its high hardness and corrosion resistance extend the lifetime of the tool. This alloy system is also well-suited to additive manufacturing, which can be utilized to form internal cooling channels, further increasing tool life. Using Rapid Alloy Development (RAD) Oerilkon METCO is developing a new composition of stainless maraging tool steel that has high hardness/strength, is corrosion resistant, and has additive-capable melting and solidification properties. This study tests the hardness and corrosion resistance of the new RAD alloys against the current market competitor Corrax …
Non-Destructive Material Analysis Of Metals And Composites Via Thermography, Jonathan R. Doubt, James L. Chapman
Non-Destructive Material Analysis Of Metals And Composites Via Thermography, Jonathan R. Doubt, James L. Chapman
Materials Engineering
The Naval Surface Warfare Center, Port Hueneme Division, is interested in the development of non-destructive damage assessment of shipboard materials via drones at distance. Long Pulsed Thermography (LPT), a method of non-destructive evaluation, was investigated as a possible method for detecting damage in metals (5005h24 Al alloy and 1008 carbon steel) and composites (aramid fiber honeycomb sandwich structure) at distances from 0.5 m to 3.0 m. LPT was conducted using two 1000 W can lights to heat the samples, and a FLIR E8-XT thermal camera. The images were then analyzed using ImageJ software to determine if damage could be detected …
Effect Of Oxygen Equivalence On The Strength And Toughness Of Ti-6al-4v Forgings, Kira Baylor, Clarissa Drouillard
Effect Of Oxygen Equivalence On The Strength And Toughness Of Ti-6al-4v Forgings, Kira Baylor, Clarissa Drouillard
Materials Engineering
Tensile testing and fracture toughness testing were conducted to establish a numerical relationship between interstitial content and performance in forged Ti-6Al-4V. The value of oxygen equivalence was used to represent the interstitial content by combining the weight percent of oxygen, carbon, and nitrogen. The correlation between oxygen equivalence and mechanical properties can be used to accurately predict the performance of forged parts. Samples of forged parts with varying levels of interstitial content were subjected to a recrystallization anneal at 75 F below the beta transus temperature to decrease microstructure variability across parts with a second anneal at 1300 F to …
Effect Of Distal Core Flattening On 304 Stainless Steel Guide Wires, Khanh Phan
Effect Of Distal Core Flattening On 304 Stainless Steel Guide Wires, Khanh Phan
Materials Engineering
Abbott Vascular produces a variety of medical guide wires to accommodate a wide array of minimally invasive medical procedures. Certain types of these wires have the distal core flattened to improve specific properties such as flexibility and steerability. However, it is unknown how this affects the other mechanical properties of the wire. Abbott Vascular provided two types of wire to test the effects of distal core flattening on the mechanical performance of the wires. One group of wires was made from 304 single spring stainless steel with no flattening performed. The other group of wires was made from 304 triple …
Newly Developed Antifouling Coating Alloys For Hydraulic Cylinder Applications, Christopher Liam Fahey, Robin Ashley Payne
Newly Developed Antifouling Coating Alloys For Hydraulic Cylinder Applications, Christopher Liam Fahey, Robin Ashley Payne
Materials Engineering
In a marine environment solid surfaces are subject to corrosion and fouling, which is the buildup of unwanted material such as algae and barnacles, that can impede the functionality of components. The application that this project focuses on are hydraulic cylinders. Eight alloys, including three newly developed alloys, were tested for marine fouling performance. Three of the alloys were primarily NiCr, these included Inconel 625, Metco 1720, and P105-X3. Four alloys contained varying amounts of Cu, and these were Monel 400, CuproNickel, Monel 450, and P76-X24. Finally, one sample of a Co-based alloy was also tested, Ultimet. Of the samples …
Effect Of Dissolved Oxygen On Corrosion Of Carbon And 13cr Steel In A Brine Environment, Kevin Peter Iu, Andy Zhou
Effect Of Dissolved Oxygen On Corrosion Of Carbon And 13cr Steel In A Brine Environment, Kevin Peter Iu, Andy Zhou
Materials Engineering
Oxygen corrosion is a major threat to seawater injection systems that are part of offshore drilling operations. Seawater is typically deoxygenated to an industry standard of(DO) by injection through a deaeration column followed by treatment with oxygen scavenging chemicals. Commercial simulation software like OLI Studio: Corrosion Analyzer predicts high corrosion rates when injection seawater contains high DO levels, justifying deoxygenation. However, a notable lack of experimental data exists concerning the effect of varying levels of dissolved oxygen on corrosion rate. The goal of this project is to measure the effect of three dissolved oxygen levels (0, 62, and 620 ppb) …
Strengthening Of 7175 Aluminum Alloy Through Multi-Step Aging Process, Colin E. Masterson, Ryland W. Jolliffe
Strengthening Of 7175 Aluminum Alloy Through Multi-Step Aging Process, Colin E. Masterson, Ryland W. Jolliffe
Materials Engineering
7175 is a heat-treatable aluminum alloy commonly used in aerospace forgings. This alloy is aged with a multi-step heat treatment. This treatment must balance strength with stress corrosion cracking resistance through a degree of overaging. The team was tasked by Weber Metals to increase the strength of this treatment without sacrificing stress corrosion cracking resistance. Both two-step and retrogression and reaging treatments were tested in experiments to find a heat treatment that could increase the yield and tensile strength by 1-2 ksi while maintaining a minimum electrochemical conductivity equivalence of 38% relative to copper. Two-step aging is the more conventional …
Metallurgical And Thermal Processing Investigation Of Additively Manufactured Superalloys Jbk-75 And Nasa-Hr-1, Allyse Birken, Derek Noel
Metallurgical And Thermal Processing Investigation Of Additively Manufactured Superalloys Jbk-75 And Nasa-Hr-1, Allyse Birken, Derek Noel
Materials Engineering
Aerojet Rocketdyne is investigating the use of directed energy deposition (DED), an additive manufacturing process, to reduce cost and lead time for manufacturing complex rocket engine components for their RS-25 engines. JBK-75 and NASA-HR-1, two Fe-Ni-base, age-hardenable (γ′) superalloys, are used for nozzle structural jackets and hot gas manifolds. Currently, these parts are produced using traditional forging or casting methods followed by intensive machining operations. Additionally, these alloys were designed for use in the wrought condition and require a different set of post-processing heat treatments when produced using DED due to their dendritic, segregated microstructure in the as-built condition. Homogenization …
Effects Of Ring Rolling On Grain Size In Inconel 718 And Waspaloy, David Webster
Effects Of Ring Rolling On Grain Size In Inconel 718 And Waspaloy, David Webster
Materials Engineering
Carlton Forge Works, an industry leader in the manufacture of rolled rings, has observed anomalous grain structures in parts made from Inconel 718 and Waspaloy. These take the form of unusually large grains at the surface of the rings, causing them to fail industry grain size standards. Grain size testing is a critical part of evaluating parts before they are used as grain size and structure control many mechanical properties including creep resistance, low and high cycle fatigue life, and yield strength. These unusually large grains are only present within the first tenth of an inch of the surface of …
Microstructure And Tensile Properties Of Close-Die Forged Ti-6al-4v Aircraft Engine Mount, Renee Roeder, Nick Chen, Michael Viksne
Microstructure And Tensile Properties Of Close-Die Forged Ti-6al-4v Aircraft Engine Mount, Renee Roeder, Nick Chen, Michael Viksne
Materials Engineering
The microstructural characteristics of a Ti-6Al-4V close-die forging that passes yield strength specifications are examined and found to be consistent with literature recommendations. Originally, the intent was to compare the microstructure of a forging that passed specification to the microstructure of a forging that did not pass specifications using the imaging software ImageJ. Due to time and safety constraints considering the COVID-19 pandemic, the data that is presented is incomplete data on only the forging that passes specifications. There are no comparisons between the forging that did not pass and the forging that passed.
Pitting Corrosion Of Oerlikon’S Abrasion Resistant Ferritic Stainless Steels, Matthew P. Nalty, Emma Wagstaff
Pitting Corrosion Of Oerlikon’S Abrasion Resistant Ferritic Stainless Steels, Matthew P. Nalty, Emma Wagstaff
Materials Engineering
Existing hardfacing coatings for hydraulic cylinders and brake disc applications crack during use leaving the components susceptible to corrosion. To address this problem, Oerlikon has designed three new alloys to be abrasion and corrosion resistant. This paper reviews the literature necessary to understand and quantify pitting resistance of stainless-steel alloys. It documents one round of testing ASTM G48 method A: Ferric Chloride Pitting Test of Stainless Steels on the new alloys P72-X9, P72-X13, P129-X9, as well as samples of 431, 316, and 2205 stainless steels. This paper also discusses improvements to the G48 testing method and industry use of the …
Alternative To Custom 450© Stainless Steel For Use In Investment Cast Golf Club Heads, William Henry Armstrong Iv, Davis Martin Loen
Alternative To Custom 450© Stainless Steel For Use In Investment Cast Golf Club Heads, William Henry Armstrong Iv, Davis Martin Loen
Materials Engineering
This investigation seeks to improve on the mechanical property of yield strength, while maintaining 10% elongation prior to fracture observed with of Custom 450 stainless steel in an air-melted investment casting operation. Improving this performance includes an additional heat treatment step of homogenization, as well as replacing the alloy. After identifying and downselecting available high strength stainless steels, a trial of Custom 455 stainless steel is recommended due to its high strength compared to the other alternative alloys. A trial has been developed to analyze the effect air melting has on the chemical composition and mechanical properties of Custom 455 …
Failure Analysis Of Investment Cast Near-Alpha Titanium Alloys, Garrett Ryan Bader, Jonathan Anton Linquist
Failure Analysis Of Investment Cast Near-Alpha Titanium Alloys, Garrett Ryan Bader, Jonathan Anton Linquist
Materials Engineering
In this project, fracture surfaces of three titanium investment castings were studied as part of a failure analysis on a TaylorMade metalwood. The crack formation occurred between investment cast Ti 9-1-1 and rolled Ti 6-4 joined by laser beam welding. The microstructure of the Ti 9-1-1 contained alpha colonies in large prior beta grains, while the Ti 6-4 was primarily Widmanstätten in basket weave morphology, refined with subsequent rolling. Over a period of cyclic loading, cracking occurred at the face-sole transition in the metalwoods that had been cast from a certain supplier B, while metalwoods that had undergone similar treatment …
Effects Of Surface Finish On High Cycle Fatigue Of Inconel 718, Jessica A. Mcroskey, Matthew Busse
Effects Of Surface Finish On High Cycle Fatigue Of Inconel 718, Jessica A. Mcroskey, Matthew Busse
Materials Engineering
Inconel 718 is a nickel-based superalloy and commonly used rocket engine material due to its excellent properties at elevated temperatures. Its fatigue life relies heavily on the surface roughness, as fatigue introduces and propagates cracks at the surface. Part standards set by Aerojet Rocketdyne typically necessitate surface roughness values from 64 to 125 Ra. However, surface topography and residual stresses incurred from the finishing process also affect the fatigue performance. The specific goal of the project is to perform a literature review and write experimental methods to determine how the surface roughness, topography, and residual stresses from turning, grit blasting, …
The Effect Of Distal Core Flattening And Heat Treatment On 304 Stainless Steel Guide Wires, Andrew Spencer Yap, Bryce Eric Veit, Matthew Frederick Lopez Villena
The Effect Of Distal Core Flattening And Heat Treatment On 304 Stainless Steel Guide Wires, Andrew Spencer Yap, Bryce Eric Veit, Matthew Frederick Lopez Villena
Materials Engineering
The mechanical response of 304 stainless steel guide wires due to different temper conditions and amounts of flattening is to be explored in this project. For this specific project, there is no public literature on the mechanical properties of guide wires with the above conditions through tensile testing or Turns to Failure Testing. To address this, the project with Abbott Vascular will measure the mechanical properties of guide wires using the aforementioned factors. Due to a lack of previous literature on this research topic, there are no quantitative goals for the project, however, any new research compiled in this area …
Discontinuous Grain Boundaries Of Forged René 41, Aaron Rabin, Bryce Bitter
Discontinuous Grain Boundaries Of Forged René 41, Aaron Rabin, Bryce Bitter
Materials Engineering
Certain nickel-based alloys, particularly René 41, characteristically have many low-angle grain boundaries (grain arrangements of less than 15 degrees), present in the microstructure of an in-use component. Frequently, these low-angle grain boundaries are not optically visible after the etching process, leading to the phenomena of discontinuous grain boundaries. There exists a risk for René 41 grain boundary characterization; since one cannot assume that a grain boundary continues beyond a discontinuity, the grain size requirements become difficult to meet. Despite favorable characteristics of René 41, such as the corrosion and oxidation resistance coupled with excellent strength at high temperatures, the risks …
Erosion Resistance Of Tungsten-Carbide Coatings For Steel Pipes In Fluid Catalytic Cracking Units, Davis Vannasing, Jennifer Hulfachor
Erosion Resistance Of Tungsten-Carbide Coatings For Steel Pipes In Fluid Catalytic Cracking Units, Davis Vannasing, Jennifer Hulfachor
Materials Engineering
In petroleum processing, the flow of catalyst readily leads to erosion of piping in a fluid catalytic cracking unit. Advances in coating materials and processes necessitate a re-evaluation of current protection methods. Commercially available tungsten-carbide (WC) claddings and nanostructured WC-W CVD coatings were investigated as potential alternative erosion-resistant coatings. Erosion tests by solid particle impingement were conducted on 2 variations of claddings and 1 variation of WC-W coatings following ASTM standard G76. A36 steel coupons were used as reference samples. For statistical validation, 2-3 replications of the tests were performed for the claddings and WC-W coating. Testing was conducted using …
Investigation Of Copper Infiltration Alloys For Use In Metal Matrix Composite Drill Bits, Samuel J. Stueland, Timothy P. Markiewicz
Investigation Of Copper Infiltration Alloys For Use In Metal Matrix Composite Drill Bits, Samuel J. Stueland, Timothy P. Markiewicz
Materials Engineering
A newly developed copper-based alloy, P98-X1 was tested for compressive strength to predict qualitative performance compared to MF53, F-Bronze, CuNiSn, and CuMnNi for use as the infiltration alloy in metal matrix composite (MMC) drill bits. Ingots of each alloy were cast using an arc furnace and cut into compression testing samples using wire electrical discharge machining (EDM). The alloys were selected for testing based on solid solution strengthening coefficient and melting point. Five of each alloy were compression tested to determine yield strength of the infiltration alloy. Yield strength was determined using a 0.002mm displacement offset from the linear elastic …
Rotating Beam Fatigue Of Forged 2219-T852 Aluminum Alloy, Julio Escamilla, Madison Reed
Rotating Beam Fatigue Of Forged 2219-T852 Aluminum Alloy, Julio Escamilla, Madison Reed
Materials Engineering
2219 aluminum has been used extensively in aerospace applications due to its ability to retain strength in large section thicknesses, thus making it ideal for large forgings. However, the Metallic Materials Properties Development and Standardization (MMPDS) handbook, a source of design data for aerospace industry applications, lacks information on 2219 in the T852 condition, particularly concerning the behavior of the alloy under cyclic loading conditions. Data was collected for forgings of 2219-T852 aluminum as produced by Weber Metals to determine the fatigue life of the alloy-temper combination and to assess the effects of forge thickness and orientation on fatigue life. …
The Impact Of Preheat On 2205 Duplex Stainless Steel Welds, Angelee G. Q. Breuninger, Iris I. Li, Cristian V. Sion
The Impact Of Preheat On 2205 Duplex Stainless Steel Welds, Angelee G. Q. Breuninger, Iris I. Li, Cristian V. Sion
Materials Engineering
The goal of this project is to determine the relationship between preheat temperature and phase balance of austenite and ferrite in the heat affected zone (HAZ) of a dissimilar thickness weld made of Sandvik SAF 2205 duplex stainless steel (DSS). Various preheat temperatures were applied (no preheat, 63°C, 98 °C, 141 °C, 181 °C, and 214 °C) to a 2-inch thick plate that was welded to a 0.072-inch thin sheet, with a 0.125-inch standoff, using manual gas tungsten arc welding (GTAW). Welding variables (voltage, amperage, and travel speed) were recorded and thermocouples were placed along the backside of the weld, …
Microstructural Transformation Of Cold-Sprayed Grcop-42 For Rocket Engine Combustion Chamber Liners, Mason Souther
Microstructural Transformation Of Cold-Sprayed Grcop-42 For Rocket Engine Combustion Chamber Liners, Mason Souther
Materials Engineering
Rocket engines have always relied on high-conductivity copper liners to protect structural components from extreme thermal loads produced by combustion. Forged NARloy-Z has been the material of choice for decades but increasing cost of its constituent silver and high waste in the machining process has reduced the alloy’s cost effectiveness. Aerojet Rocketdyne wants to determine the viability of cold-spray additively manufactured GRCop-42 as a replacement alloy to reduce liner cost. Screening tests were performed to observe the microstructural development and microhardness changes of cold-sprayed GRCop-42 after being subjected to multiple stages of the typical heat treatment of a combustion chamber …
Weld Fracture Between C450 Stainless And C300 Maraging Steels In Golf Club Heads, Emily Oreste, Shea Costner
Weld Fracture Between C450 Stainless And C300 Maraging Steels In Golf Club Heads, Emily Oreste, Shea Costner
Materials Engineering
This project studied fractures along the weld on the face of TaylorMade metalwood golf clubs. The weld joint investigated was between investment cast C450 stainless steel and hot rolled C300 maraging steel that had been joined by plasma arc welding (PAW). Cracking in the welds between these two metals was discovered during in-house prototype testing. To understand the differences between the clubs with intact weld joints and clubs with fractured weld joints, the microstructures throughout the weld zones were imaged and a grid of microhardness values of the entire sample cross-section was generated. The images and hardness values were analyzed …
Investment Cast C450 Microstructural Characterization In Golf Club Heads, Kenneth Yin-Fai Lau
Investment Cast C450 Microstructural Characterization In Golf Club Heads, Kenneth Yin-Fai Lau
Materials Engineering
Two types of tensile bars were observed in this study of golf iron heads for TaylorMade Golf. As-cast and as-cast then machined tensile bars. The tensile bars underwent tensile tests to observe tensile strength, percent elongation, and fracture mechanisms. Furthermore, the hardness of the tensile bars was also taken despite seeing no difference in sample types. However, the as-cast samples did not consistently meet the requirements of percent elongation > 10.00% as there was a sample with 0.00% and another with 1.26%. These samples also showed brittle fracture, instead of the desired cup-and- cone ductile fracture. To investigate further, transverse sections …
Modifying Casting Parameters To Improve The High Temperature Ductility Of Investment Cast Nickel-Based Superalloy Pwa 1455, Lars Alexander Hedin, Cole Magnum Introligator
Modifying Casting Parameters To Improve The High Temperature Ductility Of Investment Cast Nickel-Based Superalloy Pwa 1455, Lars Alexander Hedin, Cole Magnum Introligator
Materials Engineering
PCC Structurals, an industry leader in superalloy investment castings, has observed inconsistencies in the stress rupture performance of polycrystalline nickel-based superalloy PWA 1455. PCC has changed their casting parameters to reduce the thermal gradient during cooling but have been unable to correlate these changes with an increase in stress rupture elongation. Metallographic examination of past samples indicated microstructures composed of non- equiaxed dendritic grains with mean diameter of .021 inches along the test axis. A similar study on polycrystalline superalloys has indicated that excessive superheat temperatures above the liquidus can result in large grains identical to those observed, limiting the …
Effect Of Overaging On Tensile Properties Of 2219-T852 Aluminum, Austin Bitter, Tristan Koyamatsu
Effect Of Overaging On Tensile Properties Of 2219-T852 Aluminum, Austin Bitter, Tristan Koyamatsu
Materials Engineering
This project investigated the overaging performance of aluminum alloy 2219-T852 for use in high temperature applications. 2219 aluminum is an alloy containing 5.8 to 6.8 percent copper, and is classified as a high strength age hardenable alloy. The sponsor for this project, Weber Metals, hopes to use 2219 Al to replace titanium in certain applications above the thermal limits of typical high strength Al. To test its performance, they manufactured round tensile samples and delivered them in peak aged, T852 condition. These samples were then overaged at a range of times and temperatures. The times in this experiment were one …
In Situ Sem Solidification Study Of Ga And Egain: A Characterization Technique For Monitoring The Microstructural Evolution Of Liquid Metals, Jeremy Geovann Del Aguila
In Situ Sem Solidification Study Of Ga And Egain: A Characterization Technique For Monitoring The Microstructural Evolution Of Liquid Metals, Jeremy Geovann Del Aguila
Materials Engineering
Scanning electron microscopy (SEM) video recording is used to characterize the solidification of small volumes of 99.999% pure gallium (Ga) and eutectic gallium-indium (eGaIn) under a high vacuum environment. Specimen are superheated to 55℃ using a hot plate, cast into spherical droplets, and cooled in situ by means of a Peltier cooling stage. Special attention is given to the preparation of the specimen prior to viewing because of gallium and its alloys’ nature to form an oxide layer when melted and air cooled. The oxide acts as a skin that inhibits the observation of microstructural features during solidification. Heated samples …