The private placement was at $0.60 per share, representing a 15 per cent premium to the company's closing price on Monday 20 July.
DF will receive 17,808,087 fully paid ordinary shares in AAX, restricted against on-selling for 12 months.
Following completion of the placement, DF will hold a 14.5 per cent interest in AAX.
The companies have signed a Memorandum of Understanding to jointly pursue and deliver engineering, procurement and construction (EPC) projects globally to increase market share in their sectors.
Duro Felguera previously held a 4.99 per cent holding in AAX, and intends to move deeper into Canada, Australia, Asia and Africa through the alliance.
Both companies have long ties to their industries, with Duro Felguera being listed on the Madrid Stock Exchange since 1905. It currently has a market capitalisation of 0.6 billion.
AAX's expertise in mining and oil & gas solutions is complemented by Duro Felguera's established construction background, key presence in the energy sector and long history of successful EPC project delivery.
There is also said to be little overlap of current clients or markets between the companies.
AAX operates from 31 offices in 19 countries, with a major presence in the Americas, Africa and Asia. Meanwhile, Duro Felguera holds strongest in Europe, South America and Australia respectively.
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