Effect Of Matrix Microstructure Research Articles

Effect of matrix microstructure on micro- and macro- mechanical properties of 2.5D woven oxide fiber reinforced oxide matrix composites

A comprehensive learning of the mechanical behavior change mechanism of oxide/oxide composites is of great significance as a guide for their industrial applications. This study focused on examining how matrix microstructure impacted the micro- and macro- mechanical properties of the composites mainly by nanoindentation tests, macro-mechanical tests and x-ray computed tomography. The results showed that the sintering phenomenon of matrix sintered at 1200 ºC was more obvious, and there were visible transverse and longitudinal cracks. The in-situ modulus of matrix and interfacial shear modulus of the composite increased by 61.1% and 36.4%, respectively, with the increase of matrix sintering densification. Combined with these micro-mechanical parameters of the composites, the He-Hutchinson model predicted the same crack propagation modes as those obtained from fracture toughness tests. Moreover, more matrix cracks directly led to a 45.4% reduction in the flexural strength of the composites sintered at 1200 ºC compared to that sintered at 1100 ºC. In addition, a comparison analysis was conducted on the evolution of microstructure, micro- and macro- mechanical properties of 2.5D and 2D composites with the same preparation parameters.

Effect of matrix microstructure on the matrix/M2B wear interaction and its quantitative characterization in an Fe-2wt%B alloy

In sliding wear process, the wear reaction existing between hard phase and metallic matrix has an important effect on the wear performance of alloy. The purpose of this work is to quantitatively characterize the effect of matrix on the wear interaction in an Fe-2wt%B alloy. The results show that the wear interaction makes a positive contribution to the abrasion resistance of alloy, and increases with the increased Vm/Vp (where Vm and Vp show the volume fractions of martensite and pearlite respectively). Moreover, the contribution of matrix to the wear interaction changes with the Vm/Vp. When the Vm/Vp<1, the contribution is less than 0, namely the existence of matrix is detrimental to the wear interaction. Once the Vm/Vp≥1, the contribution is higher than 0, at this time the matrix plays a positive role in improving the wear interaction. Accordingly, it has been proven that increasing Vm/Vp is the key to improving the abrasion resistance of alloy when the Vm/Vp<1.

The Effect of Microstructure on Nitriding Mechanism of Cast Iron

Cast irons are widely used in the automotive industry for engine parts due to their excellent casting properties, low cost, high thermal conductivity and mechanical properties. However, the increasingly demanding expectations on an engine necessitate improved mechanical properties and corrosion resistance of cast-iron engine parts. Therefore, the nitriding of cast irons can be considered as a promising surface modification technique. In this paper, the effect of matrix microstructure and graphite morphology on the nitriding mechanism for cast irons was investigated. In the first part; in order to determine the effect of nitriding time, EN-GJV-450 compacted graphite iron samples were gas nitrided at 525 °C, with a nitriding potential value (KN) of 2 atm−1/2 at different periods of nitriding duration of 1, 3 and 6 h. The resultant microstructure characterizations show that with increasing nitriding time, the thickness of the compound layer and nitriding depth increase monotonically. In the second part, the effect of microstructure and graphite morphology on nitriding was examined on three types of cast iron (EN-GJS-500 Nodular, EN-GJV-450 Compacted and EN-GJL-250 Gray) by nitriding at the same temperature and nitriding potential as the first part, but at a nitriding duration of 6 h. The resultant microstructural characterization for the second part revealed that iron nitrides were formed at grain boundaries and around graphite particles, in addition to the surface layer. Nitrogen diffusion paths in cast irons are as follows: grain itself, grain boundaries and graphite boundaries. However, it was observed that nitrogen atoms primarily follow grain boundaries and graphite boundaries. Furthermore, the compacted graphite and gray cast-iron samples have higher nitriding depth than that of nodular cast-iron sample due to 3-D network structure of graphite. Thus, it was concluded that the graphite boundary diffusion was the differentiating factor for the nitriding mechanism in cast irons.

Effect of Matrix Microstructure on Abrasive Wear Resistance of Fe–2 wt% B Alloy

Two-body abrasive wear tests of Fe-B alloys with various matrix microstructures were performed using a pin-on-disc tribometer at a normal load of 3 N. The wear behavior was analyzed using scanning electron microscopy (SEM) and color 3D laser scanning microscopy. The results show that the Fe–2 wt% B alloy is mainly composed of a metallic matrix, M2B and M23(C, B)6. A pure pearlitic matrix occurs at a cooling rate of 0.05 °C/s, and a pure martensitic matrix forms at a cooling rate above 0.3 °C/s. Compared to the pearlitic matrix, the martensitic matrix can better support the M2B against fracture and provides higher abrasion resistance for the Fe–2 wt% B alloy. Moreover, with an increase in sliding distance, the abrasion resistance of Fe–2 wt% B alloy decreases slightly at first and then decreases rapidly. To be exact, the M2B is steadily scraped off until the critical sliding distance of 6.06 m is reached, after which the neighboring M2B fractures, leading to high material removal.

Microstructure and Mechanical Properties of High Manganese TRIP Steel

Microstructure evolution and mechanical properties of newly designed 0. 1C-6Mn-0. 5Si-1Al TRIP-aided steels under different annealing conditions and the effects of matrix microstructure before intercritical annealing on the final microstructure were studied by means of X-ray diffraction (XRD), scanning electron microcopy (SEM), dilatometric simulation, optical microstructure (OM) and tensile testing in this work. The experimental results indicate that the TRIP steel with Mn of 6% could form a considerable amount of retained austenite with good TRIP effect after a simple intercritical annealing treatment, and the matrix microstructure before intercritical annealing treatment can greatly affect the final microstructure. The original microstructure of the ferritic matrix steel was eliminated, while annealed martensite was remained from the martensite matrix steel under the same intercritical annealing conditions.

Effect of matrix microstructure on precipitation of Laves phase in Fe–10Cr–1.4W(–Co) alloys

Ferritic heat-resistant steels involving intermetallic Laves phase have drawn a growing interest for the enhancement of creep strength, while the brittleness of Laves phase may lower the toughness of the alloy. We believe it is possible to modify the morphology of Laves phase precipitates by controlling the α-Fe matrix microstructure. In order to make clear the influence of matrix microstructures on age-hardening, the precipitation behavior of Laves phase was investigated by transmission electron microscopy (TEM). The matrix of the Fe–10Cr–1.4W–4.5Co (at%) alloy is controlled by heat treatments so as to provide three types of microstructures; ferrite, ferrite+martensite, and martensite. Alloys with ferrite and ferrite+martensite matrices show age-hardening behavior comprised of two hardness peaks. At around the first hardness peak, it is revealed by TEM observation that fine particles precipitate coherently within the ferrite matrix. In the martensite matrix, most of R-phase and Laves phase precipitates exist on laths and dislocations.

Cleavage Initiation in Ti-V-N and V-N Microalloyed Forging Steels

The effects of matrix microstructure and features of non-metallic inclusion (morphology, type, volume fraction and size) on cleavage initiation in medium-carbon Ti-V-N and V-N microalloyed resulphurized forging steels have been determined by examining fracture surfaces produced in room temperature Charpy impact tests. The steels were generally Al-deoxidised but one V-N steel was Si-deoxidised. It has been found that, in the Ti-treated steel, having a ferrite-pearlite microstructure, brittle fracture initiation occurred at cracked coarse (Ti,V)(C,N) single phase or [(Ti,V)(C,N)/Al2O3/MnS] multi-phase inclusions. In the Ti-free steels, cleavage initiation was dependent on matrix microstructure and non-metallic inclusions. In the low strength Ti-free steels, with a ferrite-pearlite microstructure, the absence of a continuous grain boundary ferrite layer led to initiation from interfacing pearlite colonies. For the bainitic microstructure, cleavage initiated close to the notch, but the microstructural feature responsible could not be identified. For the ferritepearlite microstructure in the Si-deoxidised V-N steel, cleavage initiated at cracked Mn-Al-(Ca) silicate inclusions. The higher matrix strength and more continuous nature of grain boundary allotriomorphic ferrite in the V-N steel deoxidised with Al was associated with cleavage initiation from V-rich (V,Ti)(C,N)-containing inclusions. These were generally of smaller size than those in the Ti-treated steels.

Microstructure and mechanical properties of carbon–carbon composites with multilayered pyrocarbon matrix

The effect of matrix microstructure on the mechanical properties of carbon fiber felts infiltrated by isothermal chemical vapor infiltration (CVI) has been studied by optical microscopy, scanning electron microscopy and three-point bending tests. The nonbrittle fracture behavior of the investigated composites is related to multiple crack deflections caused by the interfacial sliding between pyrocarbon layers with a varying texture degree and the delamination microcracking within the highly textured pyrocarbon layer. An increase of the flexural strength is observed by the composite having a multilayered pyrocarbon matrix.

On the significance of matrix microstructure in fatigue strength of a unidirectional SCS-6/SP700 titanium alloy matrix composite

The effect of matrix microstructure on the fatigue strength of a SP700 titanium alloy matrix composite unidirectionally reinforced with SiC fibre, SCS-6, has been studied. Three kinds of composite materials associated with different matrix microstructure were prepared by giving the different heat treatments at elevated temperatures below and above the β-transus temperature of the matrix alloy after the fabrication process. The load-controlled high-cycle fatigue tests were conducted under a stress ration of 0.1 at room temperature in air. It was shown that the fatigue strength was significantly changed by the matrix microstructure. The mechanism was discussed, based on the measurement of the interfacial shear strength by the fibre push-out tests and the fatigue properties of the matrix alloy.

The effect of matrix microstructure on the tensile and fatigue behavior of SiC particle-reinforced 2080 Al matrix composites

The effect of matrix microstructure on the stress-controlled fatigue behavior of a 2080 Al alloy reinforced with 30 pct SiC particles was investigated. A thermomechanical heat treatment (T8) produced a fine and homogeneous distribution of S′ precipitates, while a thermal heat treatment (T6) resulted in coarser and inhomogeneously distributed S′ precipitates. The cyclic and monotonic strength, as well as the cyclic stress-strain response, were found to be significantly affected by the microstructure of the matrix. Because of the finer and more-closely spaced precipitates, the composite given the T8 treatment exhibited higher yield strengths than the T6 materials. Despite its lower yield strength, the T6 matrix composite exhibited higher fatigue resistance than the T8 matrix composite. The cyclic deformation behavior of the composites is compared to monotonic deformation behavior and is explained in terms of microstructural instabilities that cause cyclic hardening or softening. The effect of precipitate spacing and size has a significant effect on fatigue behavior and is discussed. The interactive role of matrix strength and SiC reinforcement on stress within “rogue” inclusions was quantified using a finite-element analysis (FEA) unit-cell model.

The effect of matrix microstructure and reinforcement shape on the creep deformation of near- γ titanium aluminide composites

The influences of composite matrix microstructure, reinforcement shape, and processing methodology have been evaluated for a series of near-gamma (Ti 3Al+TiAl) titanium aluminide matrix composites evaluated in tension and tensile-creep at 800°C. Specifically, heat treatments were imposed to evolve either fully-equiaxed or fully-lamellar composite matrices containing either dispersed particulate or high-aspect-ratio short-fiber boride reinforcement. The results indicate that the highest creep rates are associated with composites containing particulate reinforcement in equiaxed matrices, whereas the lowest rates were obtained for short-fiber reinforcement in lamellar matrices. The mechanisms controlling creep deformation are observed to rely only on the morphology and details of the matrix microstructure and are independent of the type and shape of the reinforcing phase. The enhanced work hardening tendencies of the lamellar microstructure is shown to improve creep resistance as manifested by a reduced steady state creep rate as well as prolonging primary creep to higher values of accumulated strain.

Role of matrix microstructure in the ultrasonic characterization of fiber-reinforced metal matrix composites

This work deals with the application of ultrasonic nondestructive evaluation for characterizing fiber-reinforced metal matrix composites. The method involved the use of a recently developed technique in which the fiber reinforcement acts as a reflector to incident ultrasonic shear waves. Single fiber and multifiber, single ply composites consisting of SiC fibers in several titanium alloy matrices were investigated. The ultrasonic images obtained were correlated with the results of metallographic characterization of the composites. The results showed that the ultrasonic response of the metal matrix composites is significantly influenced by the microstructure of the matrix through which the incident wave traverses. The general effects of matrix on ultrasonic wave propagation are reviewed, and the ultrasonic signals obtained from various SiC fiber-reinforced titanium alloy composites are discussed in terms of the scattering effects of matrix microstructure.

The effect of matrix microstructure on cyclic response and fatigue behaviour of particle-reinforced 2219 aluminium. II. Behaviour at 150°C : Vyletel, G.M., Van Aken, D.C. and Allison, J.E. Metall. Mater. Trans. A (Dec. 1995) 26A (12), 3155–3162

Fatigue cracking due to repeated loading has been recognized as an important distress problem in asphalt concrete (AC) pavements. The development of fatigue laws to describe the AC beams has been carried out through two main approaches: a phenomenological approach and a fracture mechanics based approach. However, both approaches, at the present time, employ regression constants that cannot truly reflect basic material properties. The primary purpose of this paper is to develop a fracture-mechanics-based fatigue law which utilizes fundamental material parameters including fracture toughness, flexure tensile strength, as well as two other physically quantifiable model parameters: damage parameter, α, and critical plastic zone length, δc. The development of a two-stage plastic zone model is presented, followed by the derivation of a fatigue crack growth law. The significance of the damage parameter, α, and critical plastic zone length, δc is emphasized, with a detailed discussion of the method to determine these parameters. The developed fatigue model is used to predict fatigue life of AC beams fabricated from a wide spectrum of mixture designs. The developed fatigue model predicts a much faster crack growth rate compared to the Paris law, and appears to be more sensitive to the ratio of the initial stress intensity factor over its critical value (Ko/Kc)

The effect of matrix microstructure on cyclic response and fatigue behaviour of particle-reinforced 2219 aluminium. I. Room temperature behaviour : Vyletel, G.M., Allison, J.E. and Van Aken, D.C. Metall. Mater. Trans. A (Dec. 1995) 26A (12), 3143–3154

The effect of matrix microstructure on cyclic response and fatigue behaviour of particle-reinforced 2219 aluminium. I. Room temperature behaviour : Vyletel, G.M., Allison, J.E. and Van Aken, D.C. Metall. Mater. Trans. A (Dec. 1995) 26A (12), 3143–3154

Effect of Matrix-Microstructure on Embrittlement Caused by High Carbon Martensite Island

Effect of Matrix-Microstructure on Embrittlement Caused by High Carbon Martensite Island

The effect of matrix microstructure on cyclic response and fatigue behavior of particle-reinforced 2219 aluminum: Part II. Behavior at 150 °C

The 150 °C cyclic response of peak-aged and overaged 2219/TiC/15p and 2219 Al was examined using fully reversed plastic strain-controlled testing. The cyclic response of peak-aged and overaged particle-reinforced materials showed extensive cyclic softening. This softening began at the commencement of cycling and continued until failure. At a plastic strain below 5 × 103, the unreinforced materials did not show evidence of cyclic softening until approximately 30 pct of the life was consumed. In addition, the degree of cyclic softening (†σ) was significantly lower in the unreinforced microstructures. The cyclic softening in both reinforced and unreinforced materials was attributed to the decomposition of the θ′ strengthening precipitates. The extent of the precipitate decomposition was much greater in the composite materials due to the increased levels of local plastic strain in the matrix caused by constrained deformation near the TiC particles.

The effect of matrix microstructure on cyclic response and fatigue behavior of particle- reinforced 2219 aluminum: Part I. room temperature behavior

The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and overaged 2219/TiC/15p and unreinforced 2219 Al were investigated using plastic strain-controlled and stress-controlled testing. In addition, the influence of grain size on the particle-reinforced materials was examined. In both reinforced and unreinforced materials, the naturally aged conditions were cyclically unstable, exhibiting an initial hardening behavior followed by an extended region of cyclic stability and ultimately a softening region. The overaged reinforced material was cyclically stable for the plastic strains examined, while the overaged unreinforced material exhibited cyclic hardening at plastic strains greater than 2.5 × 10−4. Decreasing grain size of particle-reinforced materials modestly increased the cyclic flow stress of both naturally aged and overaged materials. Reinforced and unreinforced materials exhibited similar fatigue life behaviors; however, the reinforced and unreinforced naturally aged materials had superior fatigue lives in comparison to the overaged materials. Grain size had no effect on the fatigue life behavior of the particle-reinforced materials. The fatigue lives were strongly influenced by the presence of clusters of TiC particles and exogenous Al3Ti intermetallics.

Investigation of the effects of matrix microstructure and interfacial properties on the fatigue and fracture behavior of a Ti [sbnd]15V [sbnd]3Cr [sbnd]3Al [sbnd]3Sn/SCS9 composite

The results of a systematic study of the evolution of microstructure and damage in a metastable β titanium matrix composite are reported. The effects of matrix microstructure are studied by heat treatment below the β transus which promotes a transformation from β toα + β. Similarly, the effects of the fiber/matrix interface are investigated by annealing above the β transus which promotes interfacial coarsening without significant changes in matrix microstructure. The effects of thermal exposure above and below the β transus are rationalized by considering the diffusion of α and β stabilizers. The initiation and evolution of damage in smooth speciments is also investigated under monotonic and cyclic loading using acoustic emission techniques. Tensile strength degradation and low-cycle/high-cycle fatigue lives are associated with the coarsening of interfacial dimensions during thermal exposure. Trends in the evolution of damage are also elucidated using filtered acoustic emission data and longitudinal sections of deformed specimens.

The Effect of Matrix Microstructure on Thermally Induced Residual Stresses in SiC/Titanium Aluminide Composites

This paper examines the effect of varying the microstructural composition of titanium aluminide on the evolution of residual stresses in titanium aluminide matrix composites. An analytical model is developed to determine residual stresses in fiber and matrix phases of unidirectional, SiC/Ti-Al composites subjected to axisymmetric thermal loading. The model uses elements of the concentric cylinder model and the method of cells to calculate residual thermal stresses in the presence of temperature-dependent and inelastic behavior of the fiber and matrix phases. The concentric cylinder model is employed as a geometric model for the unidirectional composite, whereas the method of cells is employed in modeling the microstructure of the titanium aluminide matrix phase. The titanium aluminide matrix consists of distinct brittle and ductile α and β phases whose volume content is varied in the present scheme to understand how the resulting residual stresses can be altered. Both spatially uniform and nonuniform variations of the α and β phases are considered. The results explain the occurrence of radial microcracks in SiC/Ti-Al composites in the presence of a β-depleted region at the fiber/matrix interface, and validate the potential of engineering the matrix phase to reduce residual stresses in these composites.

Effects of matrix microstructure on the interfacial strength in GF/PP examined by a single fiber pull-out technique

Effects of matrix microstructure on the interfacial strength in GF/PP examined by a single fiber pull-out technique