Grain Refinement Effect on the Hot-Tearing Resistance of Higher-Temperature Al–Cu–Mn–Zr Alloys

Abstract

The hot-tearing resistance of Al-Cu-Mn-Zr (ACMZ) alloys was investigated as a steptoward introducing these new cast alloys for severe duty, higher-temperature applications, such ascylinder heads for down-sized, turbocharged automotive engines. Alloy Cu compositions werevaried from 5 to 8 wt.%. Targeted Ti levels were 0.02, 0.1, and 0.2 wt.% via additions of the Al–5Ti–1B master alloy. Hot-tearing resistance was assessed by visual examination and ranking of thecracking severity in a multi-arm permanent mold casting. It was found that at high impuritycontents (Fe and Si of 0.2 wt.% each), the Al–Cu–Mn–Zr alloy with 4.95 wt.% Cu exhibited thepoorest hot-tearing resistance, irrespective of the grain refining amount. Microstructural analysisindicated an effective reduction in the grain size, as the Ti additions were increased to 0.02 and 0.1wt.% Ti via the Al–Ti–B grain refiner. The finest grain size was attained with a 0.1 wt.% Ti. Basedon the hot-tearing evaluation, it was found that the additional grain refining via the Al–5Ti–1Bmaster alloy at 0.1 wt.% Ti significantly reduces the hot-tearing susceptibility at Cu contents greaterthan 7.3 wt.% for ACMZ alloys with low Fe and Si. These findings indicate that the best hot-tearingresistance was observed at a grain refiner level of 0.1 wt.% Ti and high Cu content (greater than 7.3wt.%). This study to indicates that these Al–Cu–Mn–Zr alloys, which possess excellentmicrostructural stability and mechanical properties at elevated temperatures, can also possessexcellent hot-tearing resistance.

New-Age Al-Cu-Mn-Zr (ACMZ) Alloy for High Temperature-High Strength Applications: A Review

“…fatigue testing at larger component scale, possibility to adopt alternate component fabrication methodologies like additive manufacturing, wrought processing etc. [89]. Some of these aspects are mentioned below:…”

“…For the Al-Cu-Mn-Zr alloys, when Cu is added above 7 wt%, significant grain refinement occurs which further contributes to their excellent hot tearing resistance. In addition, when 0.1 wt% Ti is added as additional grain refiner, resultant Al-Cu-Mn-Zr alloy exhibits the finest microstructure and correspondingly, the best hot tearing resistance [89]. Ti added Al-Cu-Mn-Zr alloy was therefore speculated suitable for industrial applications [92].…”

Enhanced Mechanical Strength and Electrical Conductivity of Al–Ni‐Based Conductor Cast Alloys Containing Mg and Si

“…Hot tearing is one of the most deleterious defects in Al cast alloys during casting and solidification. Hot tearing susceptibility (HTS) is affected by various factors, such as alloy chemistry, casting parameters, solidification interval, [21][22][23][24][25] grain refining, [22,[25][26][27][28] residual liquid at the later stage of solidification, [22,25] and the formation of secondary phases during solidification. [1,7,29,30] Liu et al [1] reported that adding Ni into an Al-Zn-Mg-Cu-xNi alloy significantly reduced the HTS, which was attributed to the reduced vulnerable region during solidification, a lower cracking susceptibility coefficient, and a higher amount of eutectic Al 3 Ni.…”