A series of high-purity Ti 3 (Al 1-x Si x)C 2 solid solutions with 0

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The quest towards expansion of the Mn+1AXn design space has been accelerated with the recent discovery of several solid solution and ordered phases involving at least two Mn+1AXn end members. Going beyond the nominal Mn+1AXn compounds enables not only fine tuning of existing properties but also entirely new functionality. This search, however, has been mostly done through painstaking experiments as knowledge of the phase stability of the relevant systems is rather scarce. In this work, we report the first attempt to evaluate the finite-temperature pseudo-binary phase diagram of the Ti2AlC-Cr2AlC via first-principles-guided Bayesian CALPHAD framework that accounts for uncertainties not only in ab initio calculations and thermodynamic models but also in synthesis conditions in reported experiments. The phase stability analyses are shown to have good agreement with previous experiments. The work points towards a promising way of investigating phase stability in other MAX Phase systems providing the knowledge necessary to elucidate possible synthesis routes for Mn+1AXn systems with unprecedented properties.

The search for further control over the properties of MAX phases as well as the promise of discovering compounds with new functionalities has resulted in an increased interest in MAX solid solutions resulting from mixing in either the M, A, or X sublattices. The possibility of alloying MAX compounds not only enables finer tuning of their properties but can also be used to stabilize compounds that may otherwise be metastable in their pure state. In this letter, we present an ab initio-based investigation of the intrinsic alloying behavior in the A sublattice of Ti 2 (Al,A)C, Zr 2 (Al,A)C and Ti 3 (Al,A)C 2 MAX compounds. IMPACT STATEMENTIn this work, we present for the first time a comprehensive study of the intrinsic alloying tendencies in MAX solid solutions with (Al,A) mixing in the A sublattice. ARTICLE HISTORY

In this work, a systematic investigation of the alloying behavior on the M sub-lattice of M 2 AlC, where M is Ti,V,Zr and Hf with elements in the first transition metal row as well as Ca and Sc is carried out via a combination of alloy theoretic approaches and Density Functional Theory for 41 alloy systems. The cluster expansion formalism is used to explore the configurational space in ternary MAX phases. On the basis of their solid-solution behavior, the alloys are classified into three regimes: phase separation, weak ordering and strong ordering. Observed trends are investigated in terms of indicators at the electronic and structural levels. For the systems showing ordering, the ordered structures are identified and their structural and electronic properties are investigated. The likelihood of some of the systems to exist as solid solutions at finite temperature is discussed.