In-Situ Composites Research Articles

Revealing the Transition from Micro-Rod to Nano-Lamella Eutectics and its Hardening Effect in Niobium/Silicide In-Situ Composites

Revealing the Transition from Micro-Rod to Nano-Lamella Eutectics and its Hardening Effect in Niobium/Silicide In-Situ Composites

Filler Dispersion and Unidirectional Sliding Characteristics of As-Cast and Multi-Pass Friction Stir Processed ZrB2/AA7075 In-Situ Composites

AbstractDespite the fabrication of particulate-reinforced composites via friction stir processing (FSP), an attempt was made to utilize FSP for the homogenization of filler dispersion in ZrB2/AA7075 in-situ composites fabricated via stir casting route, with varying weight percentages of ZrB2. The friction stir processing was performed for up to three passes with 100% overlap. The as-cast and friction stir processed (FSPed) composites were characterized for their microstructural, microhardness, and tribological behavior. The microstructural features revealed the increase in the misorientation angle among grain boundaries, with an increase in ZrB2 content and a number of FSP passes. Furthermore, the homogeneity of ZrB2 particles in the Al alloy matrix was significantly influenced by the number of FSP passes, which was quantified by Lorenz curves and Gini Indices. The FSPed alloy and composites exhibited higher microhardness as compared to their un-processed counterparts. The tribological behavior was investigated for three different load levels, i.e., 15 N, 30 N, and 45 N. The slope of the wear-rate at 45 N revealed that the Al-alloy exhibited a considerable increase in wear severity, whereas as-cast and FSPed composites did not show a significant increase. Both wear-rate and coefficient of friction decreased with an increase in the number of FSP passes and ZrB2 content. The scanning electron micrographs of worn surfaces confirmed the reduction in adhesion, abrasion, and delamination with the number of FSP passes. However, the synergism among the three depicted the overall tribological behavior.

Effect of cooling slope casting and partial remelting treatment on microstructure and mechanical properties of A319-xMg2Si In-Situ composites

The present study is aimed at evaluating the effect of cooling slope casting and partial remelting on hypoeutectic A319- 8Mg2Si and hypereutectic A319- 16 Mg2Si in-situ composites on the microstructural evolution and mechanical and wear properties. The characteristics are compared with those of conventional gravity castings. The microstructural features have been characterized by optical and scanning electron microscopy and X-ray diffraction analysis. Mechanical properties viz. bulk hardness, tensile properties and dry sliding wear characteristics with change in applied normal loads have been evaluated. The fractographs and worn surfaces are examined under scanning electron microscope. From the experimental findings it is observed that, the cooling slope casting can effectively refine and globularize α-Al grains, primary and eutectic Mg2Si and promote non-dendritic structures. Partial remelting further globularizes the matrix structures but develops microporosities. Improved hardness, tensile strength and dry sliding wear properties are obtained in cooling slope castings and in combined cooling slope casting with partial remelting. The improved properties are attributed to refinement and globularization of microstructural constituents with non-dendritic structures. Positive effects of microstructural features overshadowed the negative effect of porosity to the improvement in properties.

Synthesis and air jet erosion wear behavior of aluminum – Al3Ti In-Situ composite

In the present study, in-situ aluminium-Al3Ti composites have been prepared by the addition of K2TiF6 inorganic salt into molten aluminium in a stir casting furnace. The in-situ composites have been formed at different holding temperatures and with varying amounts of K2TiF6. An air jet erosion set up is used according to ASTM G76 standard to conduct the erosive wear test Add see Fig. 2a. The erosion is caused by the impact of gas jet with suspended solid particle. The effects of stand-off distance and angle of erodent impingement on the erosion behavior of the composites are studied in detail.The microscopic analyses of the worn-out surfaces are carried out in a scanning electron microscope to understand the erosion mechanism, which governs the material removal. From the test results, it can be concluded that the weight loss is higher at 15° and 30° angles of impingement compared to 60° and 90° angles. Higher material loss is also observed at lower (10 mm) stand-off distance. This is because of the fact that at lower standoff distance the particles travel over smaller distance before hitting the sample surface and hence cause greater momentum transfer per second. This in turn causes higher material loss from the sample. Wear rate is also affected by the size of the Al3Ti phase. The size of this phase is in turn strongly dependent on the wt.% of K2TiF6 salt addition and the holding temperature during casting.

Effect of Heat Treatment on Microstructure and Tensile Properties of A356/V2O5 Insitu Composites

A 356 alloy reinforced with insitu V2O5 particles by using stir casting technique. The composites were produced by the addition of oxide particles in different weight percentage. The effect of oxide powder addition on microstructure and mechanical properties of produced composites were investigated. The effect of heat treatment on microstructure and mechanical properties were investigated by optical microscope, Microhardness tester and tension test. A significant improvement in hardness and tensile strength was revealed in the produced composite as compared to the base alloy. With the addition of oxide particles, the shape and size of eutectic Si changed which in turn affects the properties. It was observed that 2h solutionizing followed by the artificial aging was sufficient to make the structure homogenize and to produce the hardening precipitates. The improvement in the mechanical properties has been observed due to the age hardening precipitates in addition with refinement of insitu V2O5 particles.

Effect of Mg on the Corrosion Behaviour of As-Cast and Heat Treated Al–4.5Cu–3.4Fe In-Situ Composites

The influence of Mg addition on the corrosion behaviour of as-cast and heat treated Al–4.5Cu–3.4Fe in-situ composite was investigated. The composite was produced by solidification processing whereby Al3Fe intermetallic formed in-situ in Al–Cu matrix. Magnesium additions were made to the composite to modify the microstructure of the in-situ composite. Specimens were then heat treated at 580 °C for homogenization. The as-cast and heat treated in-situ composites were subjected to corrosive media comprising of NaCl + H2O2 solution and the corrosion rate was evaluated by gravimetric weight loss method. Both the as-cast and heat treated in-situ composite were found to be susceptible to intergranular corrosion (IGC), the heat treated specimens being less prone to attack. Optical and scanning electron micrographic observation of the corroded surface revealed highly corroded network in the as-cast in-situ composite. On the contrary, the heat treated composite revealed minimal corrosion network. The rate of corrosion and the IGC network for both the as-cast and heat treated in-situ composite decreases as Mg additions are increased.

High Cycle Fatigue Life Prediction of Al6061-TiB2 In-situ Composites

Fatigue characterization of metal matrix composites by experimental methods are being pursued seriously by several researchers. This is tedious and time consuming especially for complex shaped components. In recent years, finite element analysis is being exploited to predict the fatigue life of metallic components with good success. However no information is available as regards the prediction of fatigue life of metal matrix composites. Al6061-TiB2 in-Situ Composites possess high specific modulus and strength coupled with excellent wear resistance and high fatigue life as reported by several researchers. In the light of the above this paper focuses on prediction of high cycle fatigue life of Al6061 TiB2 in-situ composites by using commercial FEA software (MSC-Patran, MSC- Nastran and MSC-Fatigue). The predicted result of high cycle fatigue life of matrix alloy Al-6061 is compared with standard data available in military data handbook. The test specimen as per ASTM standard for fatigue tests was modeled and FEA mesh was created. Fatigue analysis was preceded by static analysis run. The material properties data for the insitu composites were experimentally determined.

The Microstructures and Mechanical Properties of V2O5-Doped Al2O3/TiAl In-Situ Composites by Reactive Hot Pressing Process

Al2O3/TiAl composites are successfully fabricated by the in-situ hot pressing method from the elemental powders of Ti, Al, TiO2, and V2O5. The effect of V2O5 addition on the microstructure and mechanical properties of the Al2O3/TiAl in-situ composites is investigated in detail. It is found that the as-synthesized composites mainly consist of V-dissolved γ-TiAl, α2-Ti3Al, and Al2O3 particles along with a small amount of V3Al phase, and the in-situ-formed fine Al2O3 particles tend to disperse on the grain boundaries of TiAl matrix. With increasing V2O5 content, the density and Vickers hardness of the resulting composites gradually increase, whereas the fracture toughness and flexural strength first increase and then decrease with the increase of V2O5 content. The composite with 3.5 wt.% V2O5 has the maximum value of 9.35 MPa m1/2 and 713.36 MPa for the fracture toughness and flexural strength, respectively. The toughening mechanism is also discussed in detail.

Synthesis of Fe-TiC In-Situ Composites by Plasma Smelting of Ilmenite

This article illustrates the synthesis of Fe-TiC in-situ composites using cheaper raw materials, namely, mild steel scrap, ilmenite, and petroleum coke. The composite was prepared via two routes by carbothermic smelting of ilmenite and coke in a molten pool of mild steel scrap in an extended transferred arc plasma reactor. In one of the routes, the mixture of ilmenite and coke were thoroughly mixed and fed through powder feeder (in-flight plasma condition), while in the other route the mixture was fed directly into the molten mild steel scrap (static bed condition). The experiments were carried out in 50 kW DC thermal plasma reactor under argon atmosphere. The preliminary results indicate that the composite prepared by in-flight plasma processing showed a better dispersion of TiC particles in the matrix than the static bed plasma processing.

Microstructure and Properties of Ti-TiN In-Situ Composites Prepared by Reactive Ball Milling of Ti in Ammonia Followed by Hot Pressing

Microstructure and Properties of Ti-TiN In-Situ Composites Prepared by Reactive Ball Milling of Ti in Ammonia Followed by Hot Pressing

Microstructure and Properties of Ti-TiN In-Situ Composites Prepared by Reactive Ball Milling of Ti in Ammonia Followed by Hot Pressing

Microstructure and Properties of Ti-TiN In-Situ Composites Prepared by Reactive Ball Milling of Ti in Ammonia Followed by Hot Pressing

Effect of oxidation on the toughness and strength of the co, Cr-(Cr,Co)7C3 In-Situ composite

Abstract : Some preliminary observations on the oxidation response of Co,Cr-(Cr,Co)7C3 in air at 1121 C are presented. These include weight gain and subsequent room temperature strength, hardness and toughness. The composite shows superior oxidation resistance to several other in-situ composites by virtue of its high chromium content. Oxidation enhances toughness but leads to a decrease in hardness and strength. The toughness increase is associated with fiber coarsening. (Author)

Structure and Properties of Eutectic Alloys

Eutectic materials have become the subject of considerable interest and investigation in recent years from two separate standpoints. In the first place, the freezing behaviour of eutectic alloys has been investigated as a subject in its own right over the past fifteen years. During this same period of time the concepts of fibre-strengthening were developed and put to test. This led to the second wave of interest in eutectic alloys when it was shown that several simple binary eutectic alloys after unidirectional solidification exhibited tensile deformation characteristics typical of fibre-reinforced composites. Research on eutectic composites has divided naturally between the academic institutions on the one hand where a fundamental approach is taken with regard to the structure and properties of eutectic composites utilizing low temperature binary systems, and industrial or government research laboratories on the other hand where searches for commercial high temperature pseudo-binary eutectic composites are undertaken. In the former case, work has focused on solidification microstructures and their inherent structural defects, on the crystallographic orientation relationships between eutectic phases, and on detailed analyses of the mechanical behaviour of these simple eutectic composites. In the industrial and government establishments much of the work has been of an empirical nature with the aim of discovering commercially useful eutectic composites to replace the nickel-base super-alloys as high-temperature turbine materials. The present state of the art and science of the subject has been reported in the proceedings of the conference on ‘In-Situ Composites” in Lakeville, Connecticut. The second conference in this series takes place in September 1975.