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.

Composition dependent ferro-piezo hysteresis loops and energy density properties of mechanically activated (Pb 1−x La x )(Zr 0.60 Ti 0.40 )O 3 ceramics

Abstract: In the present study, ferroelectric and piezoelectric nature of La substituted lead zirconate titanate was investigated to decide the optimum La content. (Pb1−xLax)(Zr0.60Ti0.40)O3 (hereinafter PLZT x/60/40) ceramics were synthesized using novel processing approach of high energy ball milling and cold isostatic pressing (CIP). This study deals with two types of hysteresis loops, polarization (P–E) and strain vs. electric field (S–E) loops. Energy density properties, remanent polarization (Pr), coercive field (Ec), piezoelectric charge coefficient (d33), internal macroscopic electric field (Ein), domain switching current (Imax) and strain hysteresis, normalized strain coefficient (Smax/Emax) were also calculated to study the behaviour of PLZT x/60/40 ferroelectrics. In addition, current vs. electric field (I–E) curves were traced not only to support P–E studies and determination of the Ec but also to confirm the ferroelectricity and domain switching characteristics studies. The PLZT 8/60/40 electro-ceramics not only show the highest Pr ~ 29.1 μC/cm2, Imax ~ 2 mA, unipolar strain ~ 0.25% and average d33 ~ 632 pm/V but also the lowest Ec ~ 9.4 kV/cm and strain hysteresis loss ~ 4%.

δ Precipitation in an AlLiCuMgZr alloy

Abstract: AlLi based [delta] phase has an NaTl structure (i.e., a diamond cubic) with a = 0.637nm and is an equilibrium phase in the binary Al-Li system. In heat treated binary Al-Li alloys of appropriate compositions, [delta] phase can format grain boundaries as well as within the grains. In commercially heat treated Al-Li-Cu alloys of 2090 specification, the grain boundary precipitate [delta] of the binary Al-Li system is replaced by a combination of T[sub 2](Al[sub 6]CuLi[sub 3]), R(Al[sub 5]CuLi[sub 3]) and T[sub 1](Al[sub 2]CuLi) phases. In similarly treated Al-Li-Cu-Mg alloys of 8090 specification, the copper rich T[sub 2] phase, present in the form of Al[sub 6]CuLi[sub 3[minus]x]Mg[sub x], is known to be the major coarse g.b. precipitate. The presence of an Al-Li-Cu-Mg based C phase at the grain boundaries of the commercially heat treated 8090 alloys has also been documented. No detailed study has yet been carried out to verify whether the [delta] phase can be present at the grain boundaries of the commercially heat treated 8090 alloys. Given the correlations between the g.b. phase morphology, g.b. phase chemistry, and the stress corrosion cracking resistance of these alloys, it is important that the g.b. precipitates be examined and identified. In thismore » paper results using TEM are presented to show that the [delta] phase can be present in varying amounts at the grain boundaries in an 8090 alloy when heat treated in the temperature range of 170--350 C. An examination is also made of the [delta] precipitation within the grain to establish that the T[sub 2]/[alpha]-Al interface is the dominant nucleation site for the noncoherent [delta] phase.« less

Recycling of Superalloy Scrap through Electro Slag Remelting

Abstract: Electro Slag Remelting (ESR) with a water cooled copper electrode has been used for recycling machined superalloy scrap. Careful electrode design and optimization of process parameters are necessary to achieve target composition and mechanical properties. The design criteria are discussed in detail. Coolant water flow rate and velocity need to be carefully chosen to ensure adequate cooling to the electrode. It is necessary to adopt liquid start technique while using the electrode. It is also essential to provide refractory metal (molybdenum) tips at the bottom of the electrode. These tips help in initiating and sustaining the ESR operation. The copper wall thickness should allow formation of a solid slag skin around the copper portion of the electrode to prevent electrode erosion as well as melt contamination. The superalloy scrap was charged through the annular gap between the mould and the electrode. Considering ingot chemistry, soundness and surface finish as the main criteria, ESR process parameters were optimized. Superalloy scrap of composition close to that of Nimonic 80A was remelted using the water cooled electrode. The process has potential for recycling a range of superalloy scrap and scaling up to produce large diameter ingots.