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.

Transformations in α2 + γ titanium aluminide alloys containing molybdenum : Part II. Heat treatment

Abstract: The response of as-cast structures of 12 alloys in the Ti-Al-Mo system containing 44 to 50 at. pct Al and 2 to 6 at. pct Mo to simple single step heat treatments in the temperature range 1373 to 1673 K is described. The microsegregation patterns present in the cast structure persist to a large extent after heat treatment, especially below 1673 K. However, tentative conclusions regarding phase equilibria in this temperature and composition range are drawn from the results. High-temperature equilibria are dominated by the β, α+β, and α+γ phase fields, while the β+γ phase field dominates equilibrium below 1473 K. Three major types of transformation behavior are observed: a massive α to γ transformation, which occurs within the α phase on quenching from 1673 and 1573 K in alloys centered around the 48 pct Al composition; a eutectoid transformation from α to B2+γ mixtures, which occurs at 1473 K and below in alloys centered around the 48Al-4Mo and 46Al-6Mo compositions; direct γ precipitation in β, which occurs primarily in the 44Al-6Mo composition at 1273 K and below; and finally growth of γ lamellae in α+γ lamellar structures with B2 precipitation on lamellar interfaces, which occurs over a broad range of alloy compositions and temperatures.

Aluminium matrix composites by pressureless infiltration: the metallurgical and physical properties

Abstract: Aluminium matrix composites containing a high volume fraction of silicon carbide particulates were produced by the pressureless infiltration technique. The metal matrix composites thus obtained were characterized for phase composition, microstructure, density, porosity and coefficients of thermal expansion. All composites were studied in their as-prepared condition without any further heat treatment. Behaviour of bulk properties such as thermal expansion and density was studied as a function of the volume fraction of silicon carbide within the volume fraction range 0.41–0.67. The coefficients of thermal expansion of the composites were found to vary between 14 × 10−6 and 7 × 10−6 K−1 in a non-linear fashion as a function of the volume fraction of SiC. The variation in the density of the composites was found to be linear with volume fraction in the usual manner. The results obtained were compared with existing models on the behaviour of macroscopic properties of composite materials.