Question: When did the Australian rail freight operator, whose main commodities included Aluminium oxide, become part of QR National?
Related documents: [0]  [DOC] Aluminium oxide (British English) or aluminum oxide (American English) is a chemical compound of aluminium and oxygen with the chemical formula Al O . It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium(III) oxide. It is commonly called alumina, and may also be called aloxide, aloxite, or alundum depending on particular forms or applications. It occurs naturally in its crystalline polymorphic phase α-AlO as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire. AlO is significant in its use to produce aluminium metal, as an abrasive owing to its hardness, and as a refractory material owing to its high melting point. [END] 
[1]  [DOC] Australian Railroad Group (ARG) was an Australian rail freight operator. It began operations in Western Australia on 17 December 2000 following its purchase of the Westrail freight business. It was purchased by QR National in June 2006. The main commodities hauled by ARG included grain, mineral sands, alumina, bauxite, coal, woodchips, quartz, nickel and iron ore around Western Australia. In June 2011 it ceased trading as a separate brand, and became part of QR National. [END] 
Answer: 
June 2011
June 2011