Fracture Surfaces Of Specimens Research Articles

Influence of post-consolidation on continuous carbon-fibre reinforced additively manufactured specimens in bending

Continuous carbon-fibre (CCF) additive manufacturing of composites has significant potential for production of optimised structures. However, stiffness and strength in parts are often significantly lower than manufacturer material data. For thermoset-impregnated CCF, post-consolidation of specimens has greatly increased strength. In this contribution, the effect of post-consolidation for thermoplastic CCF material is presented. Specimens were manufactured on a commercial AM CCF printer and post-consolidation was performed by rapid compression moulding. Porosity was evaluated by X-ray Computed Tomography (CT) and a significant reduction from 5.3vol.% to 1.1vol.% was yielded.Experimental testing is performed in four-point bending with as-printed and post-consolidated samples. Bending stiffness and strength data was obtained. The results show that the bending strength was below expectations in as-printed specimens. Finite Element Analysis indicates that snap-buckling of a small number of outer layers can lead to such a reduced apparent bending strength, and CT scans of fracture surfaces of as-printed specimens reveal the presence of interlaminar debonding. It is shown that post-consolidation highly improves the interlaminar bond, yielding experimentally obtained strength values close to nominal material strength, and the expected kink-band compressive failure is achieved.

Experimental study on the fretting fatigue of Inconel 718 superalloy

Fretting fatigue is a surface damage phenomenon appearing in mechanical assemblies subjected to time-varying contact forces. This type of failure is a very frequent problem in many engineering components, with special relevance in the blade-disc connections in aircraft gas turbines. In this study, different plain and fretting fatigue tests were done using different load levels and also under two different temperatures, at room temperature and high temperature (650 °C), in order to obtain the fretting fatigue behaviour in both conditions and compare them with that of plain fatigue test. The contact pair used to carry out these tests is the frequently used cylindrical pad pressed against a dog-bone test specimen with a rectangular cross-section. The material used to manufacture both elements is the often used Nickel alloy Inconel 718, which is widely used in the manufacture of gas turbine parts. Moreover, and because the material was received in annealed condition, this material was heat treated to improve its mechanical properties. Results of tests under different conditions are analysed and compared. Subsequently, the fracture surfaces for different specimens are analysed and fatigue crack growth rate under different testing conditions are presented and compared with data from the literature.

Microstructure‐Based Modeling and Estimation of Mechanical Properties of High‐Carbon Steel

Herein, attempts are made to estimate the mechanical properties using microstructure‐based finite element (FE) modeling and validate these results with the experimental results. The two high‐carbon steel specimens are hot‐rolled and air‐cooled to develop ferrite–pearlite microstructures. Different characterizations are utilized to observe microstructures as well as Vickers hardness and tensile tests are carried out to determine the mechanical properties. Two high‐resolution scanning electron micrographs are chosen for representative volume element‐based FE analyses for modeling the mechanical behavior of ferrite–cementite microstructure. Object‐oriented finite elements (OOF2) and Abaqus FEA 6.14 software are used to estimate the elastic and elastoplastic behavior assuming plane stress conditions. The correlation between cementite lamellae orientation and the predicted elastoplastic properties is investigated and compared with the experimental results. The influence of image size and mesh size on the predicted true stress–true strain behavior is discussed. The hard and brittle cementite lamellae face maximum stress while the softer ferrite matrix experiences maximum strain. It is found that strain accumulation is maximum at the interfaces of ferrite and cementite. These findings are further validated by the microvoid and crack initiation spots in the fracture surface and subsurface micrographs of broken tensile specimens.

An evaluation of mechanical properties and estimation of environmental reduction factors in welded API X70 steel pipeline in natural seawater

Due to the detrimental effect of damage induced by seawater in pipeline structures, there is a need to investigate the effects of natural seawater and air environments on mechanical properties of representative pipeline materials, to obtain useful data for estimation of their service lives. Hence, in this work, a X70 steel pipeline plate was welded using submerged arc welding technique; and subjected to air and natural seawater environments. Test specimens were soaked in seawater for twelve months at 28 °C. The parent plates, weld regions and the heat affected zones were investigated by evaluating their mechanical properties and fracture surfaces. The experimental findings revealed that the tensile strengths of parent and weld were 634.00 MPa and 674.00 MPa respectively, while the compressive stresses were 750.10 MPa and 750.40 MPa respectively with highest hardness value of 239HV. The findings also revealed that weld area and heat affected zone depend on material thickness, heat input and possible effect of residual stresses in the weldment. The fracture surfaces of test specimens showed combination of brittle and ductile failure mechanisms. Comparison of the test results revealed that seawater had significant effect on the mechanical properties and surface morphology of the API X70 steel pipeline with respect to immersion time.

Investigation of tensile and flexural properties of habesha moringa‐bamboo fiber reinforced epoxy hybrid composite

AbstractIn the present investigation, moringa oleifera and bamboo fibers extracted from Ethiopia are studied to understand their mechanical properties. Three types of woven composites namely moringa/epoxy, bamboo/epoxy and moringa/bamboo/epoxy (hybrid) are fabricated by maintaining 60 vol% fiber content. Additionally, neat epoxy samples are prepared for comparison. Tensile and flexural properties are investigated in terms of strength and modulus. Tensile test results depict brittle failure for all composites and infer increase in fracture strain of woven composites as compared with neat epoxy. Tensile modulus and strength of woven composites increase in the range of 19%–39% and 18%–281%, respectively as compared with neat ones. Flexural stress–strain profiles of neat epoxy, moringa/epoxy and moringa/bamboo/epoxy composites linear curves until failure indicating brittle mode while bamboo/epoxy composites shows non‐linear stress–strain profiles revealing non‐brittle mode of failure. Flexural properties exhibited by bamboo/epoxy and moringa/bamboo/epoxy reveal comparable properties to each other yet superior than moringa/epoxy and neat epoxy composites mainly attributed to the good bonding of constituents and compatibility. All the woven composites reveal an increase in flexural modulus and strength and are in the range of 31%–96% and 5.79%–51.12%, higher than the neat epoxy. Finally, fractured surfaces of specimens are analyzed using scanning electron microscope to understand the structure property correlations.

Formula omitted]-irradiation effect on the mechanical properties of in situ specimens made of structural epoxy adhesive and comparison with adhesive bulk behavior

This work examines the effects of γ-irradiation (up to 500kGy) on the mechanical behavior of aluminum in situ specimens bonded with 3MTM Scotch-WeldTM EC-2216 B/A Gray, a commercial two-part epoxy adhesive. Shear tests were performed, from which failure data and incipient axial stiffness were obtained. The results were compared to those of dedicated finite element models that had been tuned with the previously obtained bulk cohesive properties of the adhesive. Analytic models to evaluate stress distribution in the adhesive and joints axial stiffness were applied to validate the developed models and to explain the relatively small stiffness variance (observed both in experimental and numerical analyses results) compared to that of the adhesive Young’s modulus.On the whole, the adhesive showed a good tolerance to radiation in the interval studied, as already observed for bulk specimens. Finite element models were found to be accurate in predicting of the stiffness for the entire deformative field, while they overestimated the failure loads and displacements also applying unconservative failure criteria. This is very likely due to the significant number of defects found on the fracture surfaces of bulk specimens.

Cleavage Micromechanisms Study in a Ship Plate Steel through Four-Point Double-Notch Bend and Charpy Tests

In this work instrumented impact Charpy tests were performed to analyze the ductile-brittle transition of Grade A ship plate steels, which are composed of ferrite matrix with pearlite bands in the rolling direction (RD) and pearlite lands in the transverse direction (TD). Observations on fracture surfaces of Charpy specimens showed regions of cleavage from room to down temperatures, therefore blunt four-point double–notch bend specimens (4PBT), were also tested at 25°C, 0°C, –60°C and –196°C in RD and TD, to study cleavage nucleation and propagation mechanisms. In the RD the following four different cleavage microfeatures nucleated microcracks in the notch region of 4PBT in all test temperatures: lamellar-pearlite microstructure, pearlite-boundary, ferrite-grains boundary and grains ferrite-inclusions. However, in the TD at –60°C, close to the lower shelf, only lamellar-pearlite and pearlite-boundary microfeatures were found nucleating microcracks. Nevertheless, the higher density of microcracks was found in the RD. The biggest microcracks were developed in TD in pearlite lands of critical size, in all test temperature, which are the link for the development of microcracks of critical size, which can propagate and fracture steel plates. In RD most microcracks nucleated in a critical region of about 1mm from notch root for all test temperatures, however for the TD the critical region decreases with test temperature, from about 450 µm (+25°C), 370 µm (0°C) and 225µm (–60°C). The analysis also showed the effect of microstructure orientation on the number and size of microcracks, and microcracks arrest.

Effect of Mechanical Recycling on the Mechanical Properties of PLA-Based Natural Fiber-Reinforced Composites

The present study investigates the feasibility of utilizing polylactic acid (PLA) and PLA-based natural fiber-reinforced composites (NFRCs) in mechanical recycling. A conical twin screw extrusion (CTSE) process was utilized to recycle PLA and PLA-based NFRCs consisting of 90 wt.% PLA and a 10 wt.% proportion of either basalt fibers (BFs) or halloysite nanotubes (HNTs) for up to six recycling steps. The recycled material was then injection molded to produce standard test specimens for impact strength and tensile property analysis. The mechanical recycling of virgin PLA led to significant discoloration of the polymer, indicating degradation during the thermal processing of the polymer due to the formation of chromatophores in the structure. Differential scanning calorimetry (DSC) analysis revealed an increase in glass transition temperature (Tg) with respect to increased recycling steps, indicating an increased content of crystallinity in the PLA. Impact strength testing showed no significant detrimental effects on the NFRCs’ impact strength up to six recycling steps. Tensile testing of PLA/HNT NFRCs likewise did not show major decreases in values when tested. However, PLA/BF NFRCs exhibited a significant decrease in tensile properties after three recycling steps, likely due to a reduction in fiber length beyond the critical fiber length. Scanning electron microscopy (SEM) of the fracture surface of impact specimens revealed a decrease in fiber length with respect to increased recycling steps, as well as poor interfacial adhesion between BF and PLA. This study presents a promising initial view into the mechanical recyclability of PLA-based composites.

Impact of DLC Coating Deposition on the Fatigue Strength of Al-7075-T6 Aluminum Alloy

Abstract: Al-7075 has interesting mechanical properties but is susceptible to corrosion. Physical Vapor Deposition (PVD) of coatings results in good corrosion resistance and compressive stresses of the order of 1 GPa on the surface of metallic components. However, the impact of PVD films on the strength of Al-7075-T6 is uncertain. This paper provides a summary of the findings of the Authors’ research group in recent years on the fatigue behavior of Al-7075-T6 with and without PVD Diamond-like Carbon (DLC) coating. The results indicated that DLC-coated specimens have lower fatigue strength than uncoated specimens for lives up to about 10000000 cycles. The failure mechanism was determined by observation of the fracture surfaces of the failed specimens. The stress analysis performed confirms the experimental observation, with crack nucleation expected below the surface of coated specimens, where the highest tensile stresses occur during fatigue loading.

The Cracking of Al-Mg Alloys Welded by MIG and FSW under Slow Strain Rating.

Al-Mg alloys used in the shipbuilding industry were tested. The most commonly used alloy AW 5083 and alloy AW 5059 with higher strength properties were selected. Both native materials and their joints welded by the traditional MIG arc welding method and the friction stir welding (FSW) method were tested. Both methods are approved by classification societies which allow them to be used in construction by the shipbuilding industry. The research was carried out in two stages. The first study was an "in-situ tensile test in SEM". The surfaces of the deformed specimens' changes were observed in the vacuum chamber of a Philips XL30 scanning electron microscope. During the tests, the force and elongation of the specimen were recorded. In addition, a chemical analysis of selected precipitates was performed by energy dispersive spectrometry (EDS) using the EDAX adapter. Slip lines were observed on the surface of the tested specimens, which are arranged in bands in the native material and in a disordered manner in the joints welded by MIG and FSW methods. Cracking starts mainly through decohesion at the matrix-precipitate interfaces. In the second stage of the research, slow strain rate testing (SSRT) was carried out in accordance with ISO 7539-7:2005. The tests were carried out on a specially designed test stand, where the FT-5307 strain gauge force sensor with a measuring range of 0-16 kN was used to measure the force value. The PSz 20 transducer with a measuring range of 0-20 mm was also used. The test consisted of subjecting the specimen to increasing deformation with the strain rate έ = 1.6 × 10-6 s-1 until destruction. The fracture surfaces of the SSRT specimens were subjected to fractographic analysis using a Philips XL-30 scanning electron microscope. The results of fractographic studies after the SSRT test of the native materials and their joints welded by the MIG and FSW methods indicate that the trans-crystalline cracking mechanism is dominant, characterized by ductile fracture, and cracks are initiated at the interfaces of the precipitates with the matrix. The research results show that the plastic deformation increases and micro-cracks develop and merge into a main crack, which, after reaching the critical dimension, rapidly develops, causing the destruction of the material. The fracture micrographs of the specimens of base metals and their joints welded by FSW and MIG after the SSRT test allow us to conclude that the cracking mechanism was trans-crystalline ductile.

Microstructure and Fatigue Behavior of High-Performance Aluminum Alloy Al2024 Produced by Laser Powder Bed Fusion

Aluminum-based alloys are widely used in high-performance structural applications. Therefore, the opportunity to fabricate aluminum components using Laser Powder Bed Fusion (L-PBF) is a matter of great interest. In particular, the Al2024 alloy is extensively used for conventional part production but its processability by L-PBF remains a challenge because of its hot cracking sensitivity upon solidification. The new Reactive Additive Manufacturing (RAM) technology by Elementum 3D enables the production of innovative powders characterized by metal matrix and nanoceramic particles that can be processed using L-PBF. The ceramic nanoparticles of 2 % by weight improves properties and prevents Al2024-RAM2 alloy cracking during solidification. The present study investigates the fatigue performance of Al2024-RAM2 alloy manufactured by L-PBF using an SLM 280 HL equipment with a nominal layer thickness of 60 µm. A set of miniature vertical fatigue specimens were manufactured then underwent to a heat treatment T6. The specimens were tested in the as-built state (i.e., without any surface post-processing) under cyclic plane bending at a load ratio R = 0 at a frequency of 25 Hz. The fatigue performance was determined and compared to that of another Al-alloy produced by L-PBF. Specimens were examined by using optical microscopy and SEM analysis to determine the microstructure. The fracture surfaces of vertical specimens were investigated in the SEM to determine the mechanisms of crack initiation.

Mixed mode I/II fracture behavior and surface morphology of hard rock under dynamic loading

To investigate the dynamic mixed mode I/II fracture properties of hard rock, split-Hopkinson pressure bar (SHPB) was utilized to conduct dynamic fracture tests on cracked straight through Brazilian disc (CSTBD) diorite specimens with different mode mixities. The dynamic fracture load and fracture toughness for different crack angles or mode mixities were determined. The dynamic fracture process and crack mouth opening displacement (CMOD) of CSTBD specimens were monitored by high-speed camera and digital image correlation (DIC) technique, and the fractal and morphology characteristics of fracture surfaces were further analyzed using laser 3D scanner and scanning electron microscope (SEM). The test results indicate that the dynamic CMOD behavior is interrelated closely to the force acting on the crack surface, and the allowable CMOD corresponding to the dynamic peak load decreases with increasing crack angle. In addition, the stress-based and strain-based fracture criteria were introduced to analyze the mixed mode fracture mechanism of diorite. It is found that the GMTS criterion with small fracture process zone (FPZ) size and the EMTSN criterion have the best prediction effect for fracture toughness and crack initiation angle respectively. Observation results show that the macro fracture trajectories of primary cracks and secondary cracks are controlled by the prefabricated crack angle, while the variation in mode mixity has little impact on the meso-roughness and micro-morphology of the fracture surface. The fracture surface of CSTBD diorite specimen under dynamic load exhibits the SEM morphology features of mixed tensile-shear cracks.

A Novel Approach to Quantifying the Failure Modes of Concrete-Epoxy Interface

The failure or debonding of CEIs (Concrete-Epoxy Interfaces) in Fiber-Reinforced Polymer concrete (FRP) systems occurs in one or a combination of three modes: CC (Cohesive failure in Concrete), CE (Cohesive failure in Epoxy), and IF (Interfacial Failure). These failure modes are usually identified, and their relationships are established by human intuition, which is prone to subjectivity. This study proposes a novel method based on image processing techniques to analyze CEI fracture surfaces and evaluate their failure modes. The failure modes of CEI fracture surfaces of specimens from a 3PB (Three-Point Bending) experiment were assessed using an HVS, CIE L*a*b*, YCbCr, or RGB color space image segmentation-based image processing technique on the preprocessed images of the CEI failure sides. A manual approach was adopted to validate the accuracy of the proposed method. Comparing the failure mode (CE) obtained using the manual and the proposed methodology, an RMSE (Root Means Square Error) of 0.19, 0.10, 0.23, and 0.26 was obtained for HVS, CIE L*a*b*, YCbCr, or RGB color space, respectively. The epoxy area selected with CIE L*a*b* color space produced the most accurate evaluation of the failure modes. This study provides an accurate method of quantifying the failure modes of CEI fracture surfaces. The methodology proposed in this study is recommended for forensic investigations to understand better the possible causes of failure in externally bounded fiber-reinforced polymers.

Effect of Particle Sizes and Contents of Surface Pre-Reacted Glass Ionomer Filler on Mechanical Properties of Auto-Polymerizing Resin.

Herein, the mechanical properties of an auto-polymerizing resin incorporated with a surface pre-reacted glass ionomer (S-PRG) filler were evaluated. For this, S-PRG fillers with particle sizes of 1 μm (S-PRG-1) and 3 μm (S-PRG-3) were mixed at 10, 20, 30, and 40 wt% to prepare experimental resin powders. The powders and a liquid (powder/liquid ratio = 1.0 g/0.5 mL) were kneaded and filled into a silicone mold to obtain rectangular specimens. The flexural strength and modulus (n = 12) were recorded via a three-point bending test. The flexural strengths of S-PRG-1 at 10 wt% (62.14 MPa) and S-PRG-3 at 10 and 20 wt% (68.68 and 62.70 MPa, respectively) were adequate (>60 MPa). The flexural modulus of the S-PRG-3-containing specimen was significantly higher than that of the S-PRG-1-containing specimen. Scanning electron microscopy observations of the specimen fracture surfaces after bending revealed that the S-PRG fillers were tightly embedded and scattered in the resin matrix. The Vickers hardness increased with an increasing filler content and size. The Vickers hardness of S-PRG-3 (14.86-15.48 HV) was higher than that of S-PRG-1 (13.48-14.97 HV). Thus, the particle size and content of the S-PRG filler affect the mechanical properties of the experimental auto-polymerizing resin.

Experimental study of notched tensile strength of large open-hole carbon fiber reinforced polymer laminates at low temperature

Carbon fiber reinforced polymer composites used in the aircraft structures often face the problems of open-hole and low temperature. A better understanding of the effects of low temperature and large open-hole on the tensile behaviors of carbon fiber reinforced polymer laminates is highly desirable. In this study the open-hole tensile tests on the carbon fiber/epoxy laminate-T700/SYE20005 with the stacking sequence of [0/90]4S were conducted at both room temperature and low temperature of −60 °C, where the specimens with three different ratios of hole diameter D over the specimen width W were considered. The results showed that the notched strength of the laminates decreases by 54.1% with the increase of the ratio D/W from 0.3 to 0.7 at room temperature. One interesting result is that low temperature greatly improves the strength of laminates with the ratios of D/W = 0.3 and 0.5, producing the increase of 13% in the notched strength, while it has an unobvious effect on the laminate with the ratio of D/W = 0.7. The observations of fracture surface of specimens show that the failure of the laminate with small open hole is mostly dominated by the fiber breakage and axial splits, and the interlaminar delamination and intralaminar matrix cracks are also found for the laminated specimen with large open hole.

Study on Defect Evolution of Steel Strip under High-speed Cold Rolling

In this paper the strain rate effect of the material was quantitatively tested by INSTRON tensile testing machine and Zwick/Roell HTM5020 high-speed tensile testing machine. The dimple size of the fracture surface of the tensile specimen was determined and analyzed by using the scanning electron microscope. Based on the Cowper-Symonds constitutive model, the parameters in the dynamic constitutive model and the true stress-strain curve under quasi-static condition were obtained by combining the results of quasi-static and dynamic tensile tests and the finite element numerical analyses. Considering the strain rate effect of the material the effects of cold rolling speed on the evolution of different types of defects were analyzed by the ANSYS/LS-DYNA dynamics code. The results show that with the increasing of crack length and decreasing of crack width, the critical rolling speed decreases. But if the crack length is less than 5 mm and the aspect ratio of crack length to crack width is larger than 5, the critical rolling speed of crack growth can be much large.

Fracture of aircraft titanium alloys under high-frequency loading

The paper is devoted to the problem of fatigue failure of two-phase titanium alloy VT3-1 under the action of high-frequency cyclic loading. Samples for the tests were made from the compressor disk of aviation engine D30-Ku installed on Tupolev Tu-154 planes. Repeated alternating loading was carried out by displacements of small amplitude at 20 kHz, coinciding with the first harmonic of longitudinal elastic vibrations of the sample. Analysis of specimen fracture surfaces shows predominant subsurface fracture. Analysis of areas of fatigue nucleation allows identifying elements of microstructure associated with crack nucleation. The results of the study can be used in the interpretation of fracture scenarios of structural elements in operation. Increasing the resource of products under such loads is possible through the use of damping layers or tapes, where possible.

Comparative study of weld‐line strength for unfilled and glass‐filled thermoplastic polyamide‐6 materials

AbstractThe injection molding process is widely accepted for the processing of engineering thermoplastics due to the ease of manufacturing complex designs. Weld‐line is a defect occurring in injection molded parts when two flow fronts join each other. At weld‐line locations, parts exhibit lower mechanical strength mainly due to inadequate intermolecular diffusion and fiber orientation anisotropy. The present work is aimed at investigating and comparing weld‐line strength for unfilled and glass‐filled polyamide‐6 materials. To achieve this, polyamide‐6 unfilled, 30% glass‐filled, and 50% glass‐filled materials are used to manufacture plaques. The special‐purpose mold is designed to obtain plaques with and without weld‐lines with help of Moldflow simulations. The specimens for tensile tests are then cut from molded plaques and experimental testing is conducted to evaluate tensile properties. Fractured surfaces of specimens are examined using a scanning electron microscope. The results demonstrated a significant drop in tensile strength and modulus for glass‐filled material weld‐line specimens when compared to specimens of no weld‐line. However, for unfilled specimens, tensile strength and modulus are almost the same for samples with and without weld‐line. A reduction in tensile strength of 13%, 49%, and 57% is observed for unfilled, 30% glass‐filled, and 50% glass‐filled polyamide‐6 material respectively.

Fire impact on mechanically failed graphite/epoxy composites

AbstractAircraft crashes often initiate or accompany fire incidents. Post‐crash fires, in particular, can mask or destroy critical fractographic failure features necessary for accident reconstruction. As a first step in developing a coherent strategy for composite aircraft post‐crash forensic analysis, a series of vertical flame tests were performed on mechanically failed Cytec T40‐800/Cycom® 5215 graphite/epoxy unnotched compression, short beam strength, and in‐plane shear specimens. Visual inspection and scanning electron microscopy were used to examine the specimens fracture surfaces before and after fire testing. The fire‐induced damage included matrix decomposition, melt dripping, char, soot, delamination, and residual thickness increases. The composite thermal degradation was significantly influenced by the specimen stacking sequence, the fracture surface morphology, and the total available free surface area. In addition, microscopic inspection showed that char layers impeded heat conduction and oxygen transfer to the interior of the specimens resulting in less thermal damage to the underlying plies. Moreover, burned specimens with more available free surface area sustained more thermal degradation and fire combustion damage for a given fire exposure duration. Exposed fiber bundles from the fracture surfaces were susceptible to severe thinning and thermal oxidation, which destroyed critical fractographic failure features necessary for accident reconstruction.

Influence of oxygen on performance of multi-principal element alloy as braze filler for Ni-base alloys

In manufacturing of multi-principal element alloys (MPEAs), the casting process is often a primary point of oxygen introduction to the material system, which was demonstrated by the laboratory scale button arc-melting process. Oxygen introduction raises concerns for the mechanical performance of these alloys if employed as structural materials alone or in engineering applications, such as serving as filler materials to enable joining of similar or dissimilar alloy pairs that are conventionally considered difficult to join. In this work, oxide inclusions in an as-cast off-equiatomic MnFeCoNiCu MPEA and Ni-base alloy braze joints made with this MPEA were evaluated by synchrotron x-ray diffraction mapping and electron microscopy. MnO was found to be prevalent throughout the cast MPEA and was chemically reduced during brazing by trace Al from the base material, Ni-base Alloy 600. Incomplete reaction of the MnO with Al, and some alternative reaction with Cr, left a mixture of MnO, Al2O3, and Cr2O3 in the as-brazed joint, with the oxides concentrated near the braze centerline due to directional solidification. In the braze joints, the non-oxide constituent phases detected were an FCC matrix and particles of Cr23C6, Cr7C3, and TiN which are all native to Alloy 600. The evolution of oxides within the brazed joints at elevated service temperatures of 600–800 °C was also evaluated. While MnO and Al2O3 were stable during high-temperature service, Cr2O3 particles grew to several hundred microns, with dissolved oxygen in the MPEA providing a significant source for oxide growth. Comparing tensile performance of the as-brazed condition with post-service conditions showed that the evolution of oxide particles contributed to an increase in strength and decrease in ductility of the brazed joints. Evaluating particle morphologies among fracture surfaces of individual specimens demonstrated that large Cr2O3 particles and continuous cluster networks of Al2O3 were the features most detrimental to total elongation. Hence, unmitigated evolution of oxygen-containing species during brazing and service conditions is detrimental to the ductility of the brazed joints, which highlights the importance of oxygen control in initial manufacturing of MPEAs for engineering applications.