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Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr 2 B 2 , AlMn 2 B 2 , AlFe 2 B 2 , AlCo 2 B 2 , and AlNi 2 B 2 . We find that the first three borides of this series are stable phases, while AlCo 2 B 2 and AlNi 2 B 2 are metastable. We show that the elasticity increases in the boride series, and predict that AlCr 2 B 2 , AlMn 2 B 2 , and AlFe 2 B 2 are more brittle, while AlCo 2 B 2 and AlNi 2 B 2 are more ductile. We propose that the elasticity of AlFe 2 B 2 can be improved by alloying it with cobalt or nickel, or a combination of them.We present evidence that these ternary borides represent nanolaminated systems. Based on SEM measurements, we demonstrate that they exhibit the delamination phenomena, which leads to a reduced hardness compared to transition metal mono-and diborides. We discuss the background of delamination by analyzing chemical bonding and theoretical work of separation in these borides.