Defence Metallurgical Research Laboratory

About: Defence Metallurgical Research Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 1208 authors who have published 2662 publications receiving 51663 citations.

Porosity alleviation and mechanical property improvement of strontium modified A356 alloy by ultrasonic treatment

Abstract: Present study investigates the role of ultrasonic treatment (UT) on microstructure modification, porosity mitigation and their influence on mechanical properties of Sr modified A356 Al alloy. Addition of Sr in trace amount (500 ppm) to A356 alloy reduces the length of eutectic Si from 15.6 µm to 0.65 µm with a concomitant increase in porosity from 0.84% to 3.59%. Ultrasonic treatment of Sr modified A356 Al alloy retains the modification of eutectic Si (0.57 µm) and reduces the specific porosity volume to 0.86%. The effect of microstructure modification and porosity mitigation reflects on the mechanical properties of A356 Al alloy. While the Sr addition to A356 alloy reduces the tensile properties, UT of the Sr added alloy results in improved tensile properties. The mechanism of microstructure modification, porosity formation and UT assisted porosity mitigation are discussed in detail. Ultrasonic cavitation assisted degasification and bi-film breakage is proposed as the governing mechanism for porosity alleviation.

Enhanced ferroelectricity and magnetoelectricity in 0.75BaTiO3-0.25BaFe12O19 by spark plasma sintering

Abstract: Spark Plasma Sintering (SPS) technique was employed to synthesize 0.75BaTiO 3 -0.25BaFe 12 O 19 composite. X-ray diffraction studies revealed that the composite consisted of both BaTiO 3 (ferroelectric phase) and BaFe 12 O 19 (ferrimagnetic phase), respectively. The SPS treated sample showed improved ferroelectric nature when compared to conventional sintered (CS) sample. Transformation from hard to soft magnetic nature was envisaged by magnetization measurements for SPS sample. A slim hysteresis loop was recorded with a low coercivity values (390 Oe) when compared to CS sample (3900 Oe). Mossbauer spectroscopy analysis indicated that the existence of a partial amount of γ-Fe 2 O 3 phase in the lattice, giving rise to soft magnetic nature. The SPS sample showed slightly higher value of magnetoelectric output of 2.95 mV/cm at 3 kOe magnetic field when compared to the CS sample (1.45 mV/cm at 3 kOe). The present investigation compares the spark plasma sintered sample with the conventional sintered sample.

Mechanical properties of high carbon Fe3Al-based intermetallic alloys

Abstract: Fe-16 wt% Al alloys containing 0.074 to 1.1 wt% carbon were prepared by a combination of air induction melting and electroslag remelting (ESR). The cast ESR ingots exhibited a two-phase structure consisting of Fe 3 AlC 0.5 precipitate in an Fe 3 Al-based matrix. The precipitate volume fraction increased with increasing carbon content of the ingot. Most of the carbon was found to be present as the Fe 3 AlC 0.5 phase. The bulk hardness of these alloys increases linearly with increasing volume fraction of the precipitates. However, the Young's modulus of these alloys was measured to be around 175 GPa and does not change significantly with change in volume fraction of the phases present. This is explained by arguing that both the matrix as well as precipitate exhibit the same modulus values for the alloys studied in the present work. Both the bulk hardness and Young's modulus follow the rule of mixture for two phase alloys. However, the same may not be true for structure sensitive properties such as yield strength, ductility and creep resistance.

Effect of Yb substitution on room temperature magnetic and dielectric properties of bismuth ferrite nanoparticles

Abstract: Effect of the Yb dopant on the structural, magnetic, and electrical properties of the multiferroic BiFeO3 have been studied. The structural properties of sol-gel derived Bi1-xYbxFeO3 (x = 0.0, 0.1, and 0.2) nanoparticles reveal the formation of a rhombohedrally distorted perovskite in XRD and a reduction in the average grain size have been observed with an increase in the Yb concentration. Microstructural studies exhibited the formation of sphere like morphology with decreasing particle size with increase in the dopant concentration. The effective doping also resulted in larger magnetization as well as coercivity with the maximum of 257 Oe and 1.76 emu/g in the Bi0.8Yb0.2FeO3 nanoparticles. Ferroelectric as well as dielectric properties of the nanoparticles were also improved on doping. The best results were obtained for the BiFeO3 nanoparticles having Yb concentration x = 0.2.