Trends in Tech Developments An industry think tank rumbled into St. Louis for the 117th A MODERN CASTING STAFF REPORT


Congress. These papers touched on new alloy developments, testing methods and process studies that will lead to higher quality castings, better plant efficiency, and expanded cast- ing end-use markets. MODERN CASTING editors


D 1 2 3 3 5 6 *Failed before yield 56 | MODERN CASTING May 2013


picked a handful of presentations that received peer reviews among the top percentile of all the presenta- tions. These papers focused on high strength aluminum, weld repair of aluminum castings, improved mold testing methodologies, compacted graphite iron casting skin analysis and computer modeling tools.


ozens of vetted scholarly papers were presented during the 117th


Metalcasting


Presentation Sponsored Research: High


Strength Cast Al-Zn-Mg-Cu: Tensile Properties (13-1569)


Authors Edward Druschitz, Robin Foley,


and John Griffin, Univ. of Alabama at Birmingham, Ala.


Background


Te 7xxx series of alloys are among the highest strength of wrought alumi- num alloys, but casting them typically results in two microstructural defects, intermetallic particles and microporos- ity. Six experimental Al-Zn-Mg-Cu al- loys were cast under 1 MPa of pressure, heat treated and mechanically tested to determine the effect of zinc to magne-


Table 1. Average Mechanical Properties of Al-Zn-Mg-Cu Tensile Bars Alloy


Zn (%) 7.9


8.1 7.9 8.2 12.5 12.4


Mg (%) 4.9


2.1 1.4 1.4 3.4 2


Cu (%) 0.9


0.9 0.9 0.9 0.8 0.6


Condition SUP


Chill (SUP Casting) HIP (SUP Casting) SUP


Chill (SUP Casting) HIP (SUP Casting) Atmospheric


Chill (Atmospheric) HIP (Atmospheric) SUP


Chill (SUP Casting) HIP (SUP Casting) SUP


Chill (SUP Casting) HIP (SUP Casting) SUP


Chill (SUP Casting) HIP (SUP Casting)


sium ratio and processing conditions on tensile properties (Table 1).


Conclusions


• Best properties were achieved in the low alloy casting (8.2Zn-1.4Mg) with the highest solidification rate.


• Te chilled solidification-under- pressure casting achieved a 468 MPa yield strength, 525 MPa ten- sile strength, and 9% elongation.


• Ductility and strength decreased as the cooling rate decreased.


• Intermetallics dominate the ultimate strength and elongation when po- rosity is minimized.


• Higher solidification cooling rates are required to ensure ductility in the alloy, even when porosity is eliminated.


Metalcasting Congress, armed with updates on the latest metalcasting advancements.


Yield * * *


538 490 522 450 *


461 464 468 464 * * * * * *


UTS 312 371 269 565 524 567 466 0


495 505 525 508 324 432 353 578 422 510


% Elongation 0.3% 0.7% 0.8% 3.6% 1.7% 3.3% 2.1% 0 %


4.0% 5.8% 9.0% 5.3% 0.9% 1.1% 0.8% 1.5% 1.4% 0.5%


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