during holding was the reason for the increase in grain size. Te fracture surfaces of tensile


samples can be used as a representa- tive means to determine the relative amounts of inclusions in samples but underestimates their potential maximum size. Fracture bars provide a better representation for the range of inclusion sizes in castings as compared to tensile samples because of the much larger sample size and increased num- ber of sampling locations. Te fracture surfaces of the ZE41A


alloy contained film-type magnesium– oxygen-based inclusions, whose poor interface with the matrix was likely the source of fracture. Te AZ91D alloy fracture surfaces contained mostly particle-type magnesium–aluminum– oxygen spinel inclusions, as well as few smaller iron- based intermetallic inclusions. Whereas ZE41A alloy was susceptible to many small inclusions, AZ91D alloy was more susceptible to few large inclusions. Te film-type inclusions for


Fig 4. Fractography of AZ91D tensile fractures Foundry A (a) and Foundry B (b) with corresponding SEM micrographs.


ZE41A would tend not to agglom- erate and are reasoned to be not as harmful as the agglomerated and faceted particle-type inclusions with large surface area observed in the AZ91D alloy.


Tis article is a summary of a manuscript published in the International Journal of Metalcasting, Elsayed, A., Vandersluis, E., Lun Sin, S. et al. Inter Metalcast (2016). For more information on the manuscript, contact the AFS technical department at 800-537-4237.


52 | MODERN CASTING March 2017


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94