Papers by Keyword: Mechanical Property

Abstract: The mechanical properties of 206 alloys are among the highest of aluminum alloys. However, these alloys are usually prone to hot tearing. It is known that the addition of silicon can reduce the hot tearing propensity and improve fluidity. However, the commercial 206 alloys used in conventional casting processes limit the silicon concentration ≤0.05 wt% to obtain good mechanical properties. However, the semi-solid forming offers a unique opportunity to increase the silicon content to improve the castability without compromise on mechanical properties. In the present paper, the development of modified 206 alloy compositions to minimize hot tearing during semi-solid forming while maintaining competitive mechanical properties is reported. The effect of high silicon contents with varying copper levels on hot tearing sensitivity is studied. The mechanical properties of a high Si 206 alloy with lowest hot tearing sensitivity are evaluated. It is found that increasing the silicon content in 206 alloys is beneficial to reduce hot tearing. The high Si 206 variants produced by the SEED rheocating process not only reduce significantly the hot tearing sensitivity but also attain superior mechanical properties.

Abstract: Several rheocasting processes have been developed or applied in the world. One of the new rheocasting processes is the limited angular oscillation (LAO), in which the molten metal is rapidly cooled and slightly mixed during initial stages of solidification. Squeeze casting (SQC) using semi-solid slurry produced by LAO (Rheo-SQC) has been developed. Microstructure and mechanical properties of squeeze cast semi-solid slurries have been investigated. Complete parts with little defects have been produced. The ultimate tensile strength and elongation of semi-solid cast samples are higher than those of the liquid cast samples. It can be concluded that the rheo-SQC is a feasible process.

Abstract: The history of Thixomolding®, its technology and commercialization are reviewed along with recent evolution of new technology afforded by its metallurgical structure. Since Thixomolding was introduced in the early 1990’s, it has developed to more than 400 Thixomolding machines in the United States, Canada, Japan, China, Taiwan, Hong Kong, Malaysia, Korea, Germany, Belgium and France. Applications have been established in the electronics/communication, automobile, military, hand tool, medical and sporting goods markets. Thixomoldings principal advantages are in net-shaping, consolidation of parts, safety, environmental friendliness, mechanical properties and microstructure. The virtuous isotropic and fine-grained Thixomolded® microstructure has opened the door to derivative thermal mechanical processing for generating nanostructured Mg products of high strength/density along with improved ductility, fatigue strength, corrosion resistance and formability. This thermomechanical processing (TTMP) has been applied recently to the Thixomolded precursor to further refine the grain size and eutectic phases to nanometer sizes - providing yield strength above 300 MPa, fatigue strength of 150 MPa along with elongation of >10%. Alloys so processed include AZ50L, AZ60L, AM60, AZ61L, AZ70L-TH, AZ80, AZ91D, AXJ810-TH and Thixoblended® alloys of higher Zn content. Microstructure is related to processing and properties, as predestined by the Thixomolded microstructure. Fiber Metal Laminate composites based on this nanoMAG TTMP Mg product have demonstrated yield strength up to 900 MPa, with modulus of elasticity of 90 GPa.

Abstract: Ti(C,N)/Fe composites samples were fabricated in vacuum and Ti(C,N) content was respectively 20vol.%, 30vol.% and 40vol.%. The relationship of microstructure and mechanical properties for Ti(C,N)/Fe composites with various Ti(C,N) content were studied. The results indicated that the flexural strength and wear resistant increased with increasing the content of Ti(C,N)in the range of 0 to 30vol.%, then decreased with further increase of Ti(C,N) content, and the fracture toughness decreases with increasing Ti(C,N) content integrally, while the Vickers hardness increased with the increase of Ti(C,N) content. The microstructure of Ti(C,N)/Fe composites is uniform, fine grains, and grains combine more closely with Ti(C,N) 30vol.%. By comparing the properties of the material was relatively good with Ti(C,N) 30vol.% at 1300°C.

Abstract: VC/Fe-based composite samples were fabricated with different volume fraction of VC in vacuum, and the content are 40%, 55%, and 70% respectively. The relationship between microstructure and mechanical properties for VC/Fe based composite with various VC content were studied. The results indicated VC content had a significant effect on the performance and organization of the VC/Fe-based composites and the effect of VC content on the mechanical properties are varied. With ratio of VC powders increased, the volume fraction of V8C7 particles formed additionally, while the fraction of Fe particles slightly decreased. The flexural strength, fracture toughness, relative density and wear resistant increased with increase of VC content in the range of 0 to 55vol. %, and then decreased with further increase of VC content, while the Vickers hardness increased with the increase of VC content. By comparing the material with 55vol.%VC would show the best combination of properties in the prepared samples.

Abstract: FBG (fiber Bragg grating) sensors are appropriate for embedding in composites manufacturing engineering. Influence of embedding FBG sensors on the composites tension, compression, CAI properties was studied in this paper. Results identified that the mechanical properties decreased obviously when a certain volume content of optical fibers embedded. FBG sensor permits the continuous monitoring of the host material when embedded in the middle 0 degree layer, consistent with strain gauges. Sensitivity coefficient of FBG sensor embedded is almost the same as that not embedded. It offers important reference value on the application of FBG sensors in aerospace composites.

Abstract: Calcium oxalate monohydrate (COM) is the primary constituent of the majority of stones formed in the urinary tract. Mechanical properties of renal calculi dictate how a stone interact and disintegrate with mechanical forces produced by shock wave and laser lithotripsy techniques. Tensile stresses may be more effective in some instances in disrupting material because most materials are weaker in tension than compression. Urinary stone containing COM as a major component was subjected to tensile, flexural and compressive strength studies in order to understand its mechanical properties in vitro. The calculated tensile breaking strength for the urinary stone from three tests varies from 0.57 MNm-2 to 1.52 MNm-2. The flexural strength and the flexural modulus of the urinary stone were calculated as 5.17 MNm-2 and 2.22 GNm-2 respectively while the observed compressive strength was 6.11 MNm-2. The chemical composition and the crystalline nature of the stone were verified using Fourier Transform Infrared spectroscopy and X-ray diffraction.

Abstract: Energetic and metallurgic wastes are widely used as Supplementary Cementitious Materials (SCM) and aggregates in order to reduce the concrete price and/or enhance its durability and mechanical properties. Ashes generated in process of Municipal Solid Waste Incineration (MSWI) feature certain similarity with conventional SCMs and thus there is a potential to utilize MSWI ashes as concrete admixtures. Unfortunately high variety of MSWI ashes is observed as consequence of differences in incinerated waste composition and also variability of applied combustion and air pollution control technology. Therefore it is necessary to evaluate the applicability of MSWI ashes individually. The present paper deals with influence of MSWI bottom ash from a Czech incineration facility on strength and Young’s modulus of cementitious mortars where the MSWI bottom ash was used as aggregates. Even though the content of ash was as high as 40 % of aggregates dosage the influence on mechanical properties was found to be not very significant. The strength was not lost by MSWI admixing, the Young’s modulus decreased somewhat.

Abstract: Bionanocomposites based on halloysite nanotubes (HNT) as nanofillers and starch as polymer matrix were prepared by melt-extrusion process using glycerol as plasticizer and glycerol monostearate as lubricant. Scanning electron microscopic (SEM) images show homogenous dispersion of HNTs in starch matrix. A Fourier transform infrared analysis (FTIR) reveals the interaction between external hydroxyl groups of HNTs with C–O–C groups of starch. Upon halloysite addition, storage modulus, Young modulus and tensile strength increase without loss of ductility.

Abstract: Abstract. The mechanical properties and microstructure of an ultrafine-grained Cu–Al alloy before and after annealing are investigated. Ultrafine-grained Cu–Al alloy samples are processed by means of rolling at ambient temperature and rolling reduction exceeds 90%. It is found that the strength of ultrafine-grained Cu–Al alloy increased rather than decreased after annealing for 1 h in the temperature range between150°Cand 300°C.Based on the microstructures observation of samples, it can be known that both the grain size and dislocation density have main effects on hardening of ultrafine-grained Cu–Al alloy which result from annealing. These investigations showed that the annealing hardening effect can be explained by the change of dislocation density and twin density.