Richard E. Miller,  The Strength and Metallography of a Bimetallic Friction Stir Bonded Joint between AA6061 and High Hardness Steel.   journal   = {International Journal of Industrial and Manufacturing Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2014, vol. 89(5). 392 - 396
    [viewed 10 December 2019]. Available from: https://publications.waset.org/pdf/9998136.