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White chromium cast irons are used as wear-resistant materials operating under conditions of intense abrasive and impact-abrasive wear. The high wear resistance of white chromium cast irons is determined primarily by the presence of a large amount (30% or more) of solid chromium carbides of the M7C3 type. At the same time, an important effect on their operating characteristics is exerted by the state of the metallic base, which can have various structures depending on the alloying conditions and the heat treatment.It is known that in abrasive or hydroabrasive wear the best wear resistance is exhibited by white chromium cast irons with a martensite matrix [1] or a matrix of martensite with metastable austenite [2]. If the structure of the base conrains even small amounts of pearlite or troostite with similar characteristics of the carbide component, the wear resistance of the metal decreases considerably [3]. Under some wear conditions (high impact loads, high-hardness abrasive) an austenite matrix can be more advantageous than a martensite one, which can be explained [4] by the high capacity of austenite for cold-hardening. In the present work we investigated the effect of the structure of the base on the hardness and wear resistance of white chromium cast irons with the aim of increasing the service life of blades of shot-blast apparatuses.Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences; Ural Automobile Plant.The need to increase the hardness of the metallic base of cast irons has become clear in the investigation of the causes of disruption of shot-blast blades made of industrially produced cast iron ICh300Khl7G5 with a predominantly austenite structure, used in the Ural Automobile Plant. Fracture surfaces of such blades exhibited strong microplastic deformation, traces of plastic forcing back of the material (Fig. 1), and individual fatigue cracks. The blades were disrupted as a result of repeated plastic deformation and, possibly, of an adhesive interaction with the shot. This indicates that the material was disrupted due to insufficient strength and hardness of the metallic base. In order to increase the wear resistance of the blades, the hardness of the metallic base should be increased with retention of the most wear-resistant and hardest carbide phase, namely, carbides of the M7C 3 type. This can be provided by increasing the amount of martensite in the structure of the base by efficient alloying and choosing an optimum regime of heat treatment.We investigated experimental cast irons for shot-blast blades with the chemical composition presented in Table 1. In order to increase the martensite temperature M n and reduce the amount of retained austenite relative to the industrially produced metal 1, the concentration of magnesium was de-

Abstract. The methods of electron microscopy, resistometry and magnetometry are used to study ten (36-38)Co − (32-36)Ni − (27-30)Al (at. %) alloys. Cast coarse-crystalline and microcrystalline alloys made by melt spinning in a helium atmosphere are considered. It is shown that the martensite start temperature M s becomes 30-50°C lower as grains are refined to 1 µ m. Replacement of 1 at. % cobalt by nickel and 1 at. % aluminum by nickel makes the temperature interval of the В2 ↔ L1 0 martensite transformation (30-60)°C and (100-110)°C higher respectively. The martensite transformation hysteresis is about 100 degrees. The melt-spun Co 38 Ni 34 Al 28 alloy with the transformation temperatures М s = 31°С, М f = -34°С, А s = -6°С, А f = 70°С and Т с = 98°С is a material possessing the magnetically controlled shape memory effect.

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