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.

Pressureless sintering of (ZrB2–SiC–B4C) composites with (Y2O3 + Al2O3) additions

Abstract: Pressureless sintering of (ZrB2–SiC–B4C) composites with (Y2O3 + Al2O3) additions has been studied. The vol.% of SiC, B4C, and (Y2O3 + Al2O3) was varied from (26, 24, and 16) to (5, 4, and 5) respectively. Hardness of composites has been found to decrease with a decrease in B4C content. Flexural strength has been found to increase with decreasing (Y2O3 + Al2O3) content. No considerable decrease in flexural strength for composite with high vol.% of SiC, B4C, and (Y2O3 + Al2O3) has been observed up to a temperature of 1500 °C. By optimizing the composition a composite possessing a density of 4.64 g cm− 3, flexural strength of 213 MPa, and Vickers hardness of 17.3 GPa has been sintered. Conical shapes could be made by manual shaping and sintering. A complex yttria-alumina-silicate (YAG) layer was found to protect the composite from oxidation at high temperature of 1700 °C. The composites exhibited good dimensional stability and thermal shock resistance at 2200 °C in oxy-acetylene flame and at 2700 °C in plasma flame. Formation of yttria stabilized zirconia embedded in the matrix of YAG has been identified on the flame exposed surfaces. The composite could be joined to itself by gas tungsten arc welding (GTAW) with a filler material containing (ZrB2–SiC–B4C–YAG). The shear strength of the weld was about 50% of the flexural strength of the parent composite.

Fracture toughness and low cycle fatigue behaviour in boron modified Timetal 834 titanium alloy

Abstract: The effect of addition of 0.2 wt.% B to Timetal 834 alloy on the fracture toughness at room temperature and low cycle fatigue (LCF) behaviour at room temperature and 600 °C was studied in the thermomechanically processed condition after subjecting it to a standard heat treatment. The fracture toughness of the boron modified alloy was found to be only marginally lower than that of the base alloy in both L–T and T–L orientations. Both the B modified Timetal 834 alloy and the base alloy exhibited cyclic softening throughout their fatigue life at a total strain amplitude of 1.0% for LCF tests at room temperature and 600 °C. The fatigue life of the B modified Timetal 834 alloy was also found to be nearly same as that of the base alloy at both room temperature and 600 °C. The observed behaviour was attributed to the fact that the microstructure of the matrix alloy remains unaffected by the addition of 0.2 wt.% B in the thermomechanically processed and heat treated condition except for the presence of about 0.015 volume fraction of TiB whiskers and this results in similar deformation and fracture mechanisms in the base and boron modified Timetal 834 alloys.

Melting, Processing, and Properties of Disordered Fe-Al and Fe-Al-C Based Alloys

Abstract: This article presents a part of the research work conducted in our laboratory to develop lightweight steels based on Fe-Al alloys containing 7 wt.% and 9 wt.% aluminum for construction of advanced lightweight ground transportation systems, such as automotive vehicles and heavy-haul truck, and for civil engineering construction, such as bridges, tunnels, and buildings. The melting and casting of sound, porosity-free ingots of Fe-Al-based alloys was accomplished by a newly developed cost-effective technique. The technique consists of using a special flux cover and proprietary charging schedule during air induction melting. These alloys were also produced using a vacuum induction melting (VIM) process for comparison purposes. The effect of aluminum (7 wt.% and 9 wt.%) on melting, processing, and properties of disordered solid solution Fe-Al alloys has been studied in detail. Fe-7 wt.% Al alloy could be produced using air induction melting with a flux cover with the properties comparable to the alloy produced through the VIM route. This material could be further processed through hot and cold working to produce sheets and thin foils. The cold-rolled and annealed sheet exhibited excellent room-temperature ductility. The role of carbon in Fe-7 wt.% Al alloys has also been examined. The results indicate that Fe-Al and Fe-Al-C alloys containing about 7 wt.% Al are potential lightweight steels.