Quenching

About: Quenching is a research topic. Over the lifetime, 22899 publications have been published within this topic receiving 224316 citations.

High strength bulk amorphous alloys with low critical cooling rates (overview)

Abstract: This paper aims to review our recent research results on new amorphous alloys. The main topics consist of the following five parts ; (1) the finding of new amorphous alloys with extremely large glass-forming ability in a number of alloy systems, (2) the mechanism for the achievement of the large glass-forming ability, (3) the clarification of fundamental properties of the new amorphous alloys, (4) the successful examples of producing bulk amorphous alloys by four different techniques of water quenching, metallic mold casting, arc melting and unidirectional zone melting, and (5) the high tensile strength of the bulk amorphous alloys. These new results enable the elimination of the limitation of sample shape which has prevented the development of amorphous alloys as engineering materials and are expected to give rise to the revisit age to amorphous alloys.

Atomic size effect on the formability of metallic glasses

Abstract: The minimum solute concentration in a binary alloy system necessary to obtain a stable amorphous phase by rapid quenching, C B min , collected from the published reports on glass formation of 66 systems, was found to be inversely correlated with the atomic volume mismatch, | (v b −v A v A | , where v A is the atomic volume of the matrix and v B is the atomic volume of the solute. The atomic scale elasticity theory was developed to calculate the atomic level stresses in solid solution, which led to the stress criteria for the topological instability of solid solution. It was found that C B min is closely correlated with the critical solute concentration for the topological instability of solid solution. This result indicates that the atomic size ratio between the constituent elements is the most important factor in the determination of value of C B min , and the amorphous alloys are stabilized partly because the solid solutions of the corresponding compositions are topologically unstable.

Martensite in steel: strength and structure

Abstract: This paper reviews the strengthening mechanisms associated with the various components of martensitic microstructures in steels and other ferrous alloys. The first section examines the experiments and strengthening theories associated with Fe–Ni and Fe–Ni–C alloys, in which the martensite, because of subzero Ms temperatures, can be evaluated with carbon atoms trapped in octahedral interstitial sites. The evaluation of strengthening in these alloys has been limited to interpreting yield strength of unaged, untempered martensite in terms of interstitial solid solution strengthening. The second section reviews strengthening of martensitic Fe–C alloys and low-alloy carbon steels with above-room-temperature Ms temperatures. In these alloys, it is impossible to prevent C diffusion during quenching, and strengthening of martensite becomes dependent on static and dynamic strain aging due to carbon atom interaction with dislocation substructure. In all alloys the dominant strengthening component of martensitic microstructures is the matrix of martensitic crystals, either in lath or plate morphology, but secondary effects due to other microstructural components such as carbides and retained austenite are also discussed.

Quenching and partitioning martensite-a novel steel heat treatment

Abstract: A novel concept for the heat treatment of martensite, different to customary quenching and tempering, is described. This involves quenching to below the martensite-start temperature and directly ageing, either at, or above, the initial quench temperature. If competing reactions, principally carbide precipitation, are suppressed by appropriate alloying, the carbon partitions from the supersaturated martensite phase to the untransformed austenite phase, thereby increasing the stability of the residual austenite upon subsequent cooling to room temperature. This novel treatment has been termed ‘quenching and partitioning’ (Q&P), to distinguish it from quenching and tempering, and can be used to generate microstructures with martensite/austenite combinations giving attractive properties. Another approach that has been used to produce austenite-containing microstructures is by alloying to suppress carbide precipitation during the formation of bainitic structures, and interesting comparisons can be made between the two approaches. Moreover, formation of carbide-free bainite during the Q&P partitioning treatment may be a reaction competing for carbon, although this could also be used constructively as an additional stage of Q&P partitioning to form part of the final microstructure. Amongst the ferrous alloys examined so far are medium carbon bar steels and low carbon formable TRIP-assisted sheet steels.