Preparation of Fe-As alloys by mechanical alloying and vacuum hot-pressed sintering: microstructure evolution, mechanical properties, and mechanisms

Arsenic materials have attracted great attention due to their unique properties. However, research concerning iron-arsenic (Fe-As) alloys is very scarce due to the volatility of As at low temperature and the high melting point of Fe. Herein, a new Fe-As alloy was obtained by mechanical alloying (MA) followed by vacuum hot-pressed sintering (VHPS). Moreover, a systematic study was carried out on the microstructural evolution, phase composition, leaching toxicity of As, and physical and mechanical properties of Fe-As alloys with varying weight fractions of As (20%, 25%, 30%, 35%, 45%, 55%, 65%, and 75%). The results showed that pre-alloyed metallic powders (PAMPs) have a fine grain size and specific super-saturated solid solution after MA, which could effectively improve the mechanical properties of Fe-As alloys by VHPS. A high density (> 7.350 g<middle dot>cm(-3)), low toxicity, and excellent mechanical properties could be obtained for Fe-As alloys sintered via VHPS by adding an appropriate amount of As, which is more valuable than commercial Fe-As products. The Fe-25% As alloy with low toxicity and a relatively high density (7.635 g<middle dot>cm(-3)) provides an ultra-high compressive strength (1989.19 MPa), while the Fe-65% As alloy owns the maximum Vickers hardness (HV0.5 899.41). After leaching by the toxicity characteristic leaching procedure (TCLP), these alloys could still maintain good mechanical performance, and the strengthening mechanisms of Fe-As alloys before and after leaching were clarified. Changes in the grain size, microstructure, and phase distribution induced significant differences in the compressive strength and hardness.