Cast alloy flakes for r-t-b rare earth sintered magnet

Cast alloy flakes for an R-T-B based rare earth sintered magnet, comprising:

• R which is a rare earth element;
• T which is Fe or a mixture of Fe and a transition metal (except for Fe and Cu);
• M which is one or more metals selected from the group consisting of Al, Ga, and Cu;
• and
• B,
• wherein the cast alloy flakes comprises R in a range of 28% by mass to 33% by mass;
• the cast alloy flakes comprises B in a range of 0.8% by mass to 1.1% by mass;
• the cast alloy flakes comprises M in a range of 0.1% by mass to 2.7% by mass;
• a remainder consists of T and inevitable impurities;
• one surface of the cast alloy flakes is a roll surface;
• and
• an area ratio of a R-rich phase on the roll surface is in a range of 0.03% to 5%.

Cast alloy flakes for an R-T-B based rare earth sintered magnet, comprising:

• R which is a rare earth element;
• T which is Fe or a mixture of Fe and a transition metal (except for Fe and Cu);
• M which is one or more metals selected from the group consisting of Al, Ga, and Cu;
• and
• B,
• wherein the cast alloy flakes comprises R in a range of 28% by mass to 33% by mass;
• the cast alloy flakes comprises B in a range of 0.8% by mass to 1.1% by mass;
• the cast alloy flakes comprises M in a range of 0.1% by mass to 2.7% by mass;
• a remainder consists of T and inevitable impurities;
• one surface of the cast alloy flakes is a roll surface;
• and
• when an R-rich phase having a short axis length of 20 μm or more is defined as a coarse R-rich phase, among the R-rich phases on the roll surface, a content of the coarse R-rich phase in the R-rich phase is 20% by number or less.