Ni-Mo-Al eutectic alloys were subjected to a process of unidirectional solidification (UDS) by the Bridgman-Stockbarger technique with a view to a composite of ductile matrix containing ductile reinforcement of comparatively high strength. The microstructure after UDS consists of a γ/γ' matrix reinforced with Mo(α) fibers. The growth direction and the orientation relationships between the phases were determined by electron diffraction. In the present study, attention was focussed on phase stability after prolonged exposure at elevated temperature. Isothermal exposure of 90 min at 1250°C was followed by a mild water quench. Apart from the beneficial influence on the γ' morphology, partial transformation of the α(Mo) fibers into δ-NiMo intermetallic was observed. Replacement of the ductile α(Mo) fibers by the brittle δ-NiMo is accompanied by partial loss of facetting. Decisive evidence of this diffusion-controlled phase transformation is supplied by TEM micrographs.

The continuous heat treatment of steel has been a widely used practice throughout the world for a considerable time. However, it is only in the past decade that the enormous potential of continuous annealing was recognized so that it is now possible to produce steels with a much wider variety of properties than is possible by batch annealing. These possibilities have been revealed not only by advances in controlling and configuring continuous annealing lines, but also in up-stream and downstream technology. These advances have made consistency the word which is synonymous with continuously annealed steel. This paper will review the fundamentals of continuous annealing and associated metallurgy, and the effect of processing variables on the product properties. The acceptable variation in processing to give an uniform product will be described.

Changes in microstructure due to phase transformation are measured for a number of laser-hardening treatments in both an Nb-microalloyed and a medium carbon steel. These measurements are correlated with theoretical predictions of laser thermal cycles and good agreement is obtained. The kinetics of the ferritic/pearlitic→austenite transformation are also discussed.

It is well known that silicon, germanium and other diamond-cubic semi-conductors may transform to a metal when a pressure of the order of 100 kilobars is applied. This renders the detailed study of the transformation experimentally difficult. Grey tin transforms to the more common (white) metal allotrope at room temperature and pressure and so provides a means of studying readily this type of transformation. This paper describes the influence of pressure on the transformation characteristics of tin and dilute tin-germanium alloys.

Recently an intermediate incommensurate phase has been found around 846 K in a small temperature range of 1.3 K between the usual α and β phases of quartz. In the neighborhood of these transitions most physical properties show drastic variations which has remained a puzzle. We shall present some measurements of the heat capacity Cp and of thermal expansion coefficients αi which present very large variations in the incommensurate phase. These divergences can be related by Pippard-Garland relations in the 3 phases. Furthermore in the low temperature α phase this result can be explained by the existence of a macroscopic order parameter η related to SiO4 tetrahedra, and varying as predicted by the Landau theory of 1st order phase transition. While in the high temperature phases (β and incommensurate) η vanishes, it takes a finite value in α phase, increasing continuously upon further cooling. However at the microscopic level, the discontinuity is reduced by the existence of the incommensurate phase, which corresponds probably to modulated tilting of SiO4 tetrahedra.

Precipitation hardening in the W-phase of the 90W-5Ni-5Fe alloy has been identified and monitored by transmission electron microscopy and mechanical tests. Deformation of the alloy prior to aging is observed to accelerate the precipitation reaction. Possible precipitate origin and geometry are discussed in terms of the TEM observations.

Recent studies carried out on weld metal have called attention to the role of oxygen-rich inclusions on austenite decomposition. This investigation describes some evidences of the catalytic effect of dislocations upon the γ → α transformation. These defects are generated at the matrix inclusion interface and its presence has been ascertained by TEM. Estimates of the stresses arising from differences in thermal contraction between inclusion and matrix on cooling confirm microstructural observations.

The bainite reactions in the direct and in the step quenched conditions were compared using Fe–7.6Ni–0.48C and Fe–3.6Ni–1.45Cr–0.50C alloys. It was found that in both alloys the bainite reactions were markedly accelerated by step quenching to temperatures even in the stable austenite range prior to the transformation to bainite. Optical microscope observation revealed that this acceleration was caused by the enhanced nucleation of bainite at grain boundaries. This enhanced nucleation by step quench treatment was considered to be due to either the formation of carbon poor areas or the formation of ferrite embryos at the grain boundaries during holding at intermediate temperatures.

Melt spinning was used to rapidly quench V2CrA11-xBx and Ti3Nb6Mo3Si4 alloys. Melt spinning had very little effect on the crystal structure of the V2CrA11-xBx alloys. However, a new (NbTiMo)3 Si A–15 phase was found by rapid quenching of the Ti3Nb6Mo3Si4 alloys; the lattice parameter was 5.08 Å. Melt spinning increased the Vickers microhardness values of the V2CrA11-xBx alloys from 500 to 750, and of the Ti3Nb6Mo3Si4 alloys from 1000 to as high as 1675. Melt spinning increased the superconducting transition temperature of the Ti3Nb6Mo3Si4 alloys from 1.9 to 3.4K.

Two zinc-aluminium based alloys with 30% Zn and 60% Zn and small additions of silicon have been quench-aged and the phase transformations studied in relation to the hardness. It was found that the peak hardness increase is due to the formation of αm ″ and α″ phases and evidence has been obtained for the transformation of these to αm ′ and α′. A cellular reaction αS ′→αT ′+η was observed in the first stage of ageing in the alloy with 60% Zn.

The alloys of the ternary system Zn-Al-Cu are characterised by dimensional changes that occur on ageing in conjunction with certain phase transformations and changes in solid solubility [1]. The phase transformation that is suggested to be responsible is the four phase reaction

that occurs below 273°C [2]. The average density of the products of this reaction was hypothesised to be less than that of the reactants resulting in an increase in volume. Previous work [3] had indicated that the lattice parameters of the zinc structure cell varied considerably on ageing and this change was attributed to the change in solubility of substitutionally dissolved copper. On ageing it is hypothesised that copper tends to come out of solution in zinc, contributing to the total increase in volume. This copper may come out as ε-phase which may react to form T'-phase with a resulting change in volume.

The influence of boundary layer on the coefficient of adhesion between fibers and matrix in polymer composites was investigated. A multilayer model was introduced consisting of the two main-phases of the composite,that is the elastic inclusion and the viscoelastic matrix and a third intermediate phase consisting of a series of cylindrical layers of mechanical and physical properties varying between the limit values of the matrix and inclusion. The extent of the interlayer between main phases may be determined from the overall properties of the composite and the matrix. The model proved to be very flexible and describes conveniently the behaviour of the material. Moreover, the model allowed the definition of an adhesion coefficient, convenient to describe the quality of adhesion of the component materials and the introduction of an improved expression for the law of mixtures in polymeric composites.