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Eco-friendly “green” composites made from flax fibers and biodegradable corn starch-based matrix were successfully prepared by hot pressing. Thermoplastic starch (TPS) was obtained by blending native corn starch with glycerin and water. The plasticized starch was emulsified before being added to the previously NaOH-treated flax fibers. The flax content was varied from 20 to 80 wt%. The composites were preheated and then pressed at 5 MPa and 160°C for 30 minutes. Density measurements showed low porosity for all composites up to 50 wt% fibers. SEM investigation showed strong adhesion at fiber-matrix interface and good fibers wettability. Static tensile and flexural mechanical properties (stiffness and strength) of the composites appeared to increase with the fiber weight fraction increase up to 50 wt%. Increasing fiber content also improved composite stability in thermal degradation, water uptake and biodegradation. Some micromechanical models are used to study the tensile strength and modulus of the obtained composites such as the Kelly-Tyson and Halpin–Tsai equations. The present work shows that 50 wt% composite has competitive properties, qualifying this material to be affordable and appropriate for different applications.

Abstract. In this research, the friction stir welding of dissimilar commercial pure aluminium and brass (CuZn30) plates was investigated and the process parameters were optimized using T aguchi L9 orthogonal array. T he considered process parameters were the rotational speed, traverse speed and pin offset. The optimum setting was determined with reference to ultimate tensile strength of the joint. The predicted optimum value of ultimate tensile strength was confirmed by experimental run using optimum parameters. Analysis of variance revealed that traverse speed is the most significant factor in controlling the joint tensile strength and pin offset also plays a significant role. In this investigation, the optimum tensile strength is 50% of aluminium base metal. Metallographic examination revealed that intermetallic compounds were formed in the interface of the optimum joint where the tensile failure was observed to take place.

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Compacted (vermicular) graphite iron (CGI) is used in many substantial applications because its vermicular microstructure has superior mechanical properties at higher temperatures. Production of vermicular graphite cast iron diesel engine cylinder block with various sections' thicknesses is a great challenge especially, if compacted graphite iron is made by controlling the pouring duration. Investigations on microstructure and hardness have been conducted on four different thicknesses (5, 10, 15, and 20 mm) of compacted graphite iron. Results demonstrated that pouring duration affects both cooling rate, and Mg/S content. These two parameters to decide the nodularity percentage and the matrix microstructure. Longer pouring duration lowers Mg/S content and decreases the cooling rate for the similar section thickness, however shorter pouring duration acts in the opposite direction. Microstructure and hardness are also affected by casting sections with the same pouring duration through different cooling rates. An increase in the cross-sectional thickness for the same pouring duration decreases the rate of cooling that encourages the formation of compacted graphite with pearlitic rather than martensitic a matrix in addition to lowers the nodular graphite count. Magnesium fading and compacted graphite ratio increased with longer pouring duration. Hardness decreased with larger section thickness and longer pouring duration due to the elimination of the martensite phase in the matrix.

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Shock resisting cold work tool steel is one of the most applicable steels for several applications such as cutting sheets, chisels, hammers, etc. It has been categorized according to its characteristic properties into different categories as hot and cold work tool steel. This work aims to study the effects of conventional and deep cryogenic treatment (DCT) on shock-resistant cold work tool steel. In this study, three alloys were cast and prepared with different carbides forming elements such as vanadium (V) and niobium (Nb). The samples were quenched in water at 900 ℃ followed by a tempering treatment at 200 ℃  for 30 min. After quenching in water, the other samples were subjected to DCT at −196 ℃  for a 5-h soaking time, followed by tempering at 200 ℃  for 30 min. To study the wear behavior of the three heats, pin-on-disc tests were used, where the sliding speed was kept constant at a value of 0.5 m/s. The normal applied loads during the wear test were 50 N and 100 N. In order to understand the wear behavior, wear tracks were studied by scanning electron microscopy, coefficient of friction and weight loss were evaluated. The results showed that the lowest average coefficient of friction was achieved by a sample of steel 3 with quenching + DCT at a load of 100 N of load by value of 0.33. A sample of steel 3 at load 50 N achieved the lowest weight loss by using DCT plus tempering. On the other hand, a sample of steel 3 achieved the lowest weight loss at 100 N by using quenching + DCT.

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