In this work, we studied the behavior of the Nd–Dy–Fe–Co–Cu–B alloy for permanent magnets under high pressure torsion (HPT). In the initial state of the studied alloy, it mainly contained the crystalline phase τ₁ (Nd, Dy)₂(Fe, Co, Cu) ₁₄B. After HPT at room temperature (T_HPT = 30°C), a mixture of an amorphous phase with nanocrystalline inclusions of the τ₁ phase is observed in the alloy. In the equilibrium phase diagram, this state is equivalent to a mixture of the τ₁ phase with the melt at the temperature T_eff= ∼1100°C. The thus determined T_eff value is called the effective temperature. When the T_HPT temperature of the HPT treatment increases to 300 and 400°C, the amorphous phase disappears, and the Fe₂B and γ-Fe phases appear instead. In the equilibrium phase diagram, this state is equivalent to a mixture of phases τ₁+ Fe₂B + γ-Fe, which is observed in the temperature range from ∼950 to ∼1050°C. We explain this phenomenon by the fact that with an increase in the HPT temperature T_HPT, the rate of formation of defects during deformation remains constant, but the rate of their thermal relaxation (annihilation) increases. This is equivalent to decrease in the effective temperature T_eff in the equilibrium phase diagram. The previously predicted decrease in T_eff with an increase in T_HPT is observed for the first time.

中文翻译：

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Nd-Fe-B基合金在不同温度下高压扭转下的相变

在这项工作中，我们研究了Nd-Dy-Fe-Co-Cu-B合金在高压扭转（HPT）下用于永磁体的行为。在所研究的合金的初始状态时，它主要包含结晶相τ ₁（ND，镝）₂（铁，钴，铜）₁₄ B. HPT后在室温（Ť _HPT = 30℃）的混合物，与τ的纳米晶的夹杂物的非晶相₁相在合金中观察到。在平衡相图中，这种状态是等效于τ的混合物₁在该温度下相位与熔体Ť _EFF = ~1100℃。因此确定的T _eff该值称为有效温度。当HPT处理的T _HPT温度升高到300和400℃时，非晶相消失，而出现Fe ₂ B和γ-Fe相。在平衡相图中，这种状态相当于相τ的混合物₁ +的Fe ₂乙+ γ-Fe等在温度范围内观察从~950至~1050℃。我们通过以下事实来解释这种现象：随着HPT温度T _HPT的升高，变形过程中缺陷的形成速率保持恒定，但是其热弛豫（an灭）的速率却增加了。这等效于有效温度的降低平衡相图中的T _eff。在先前预测减小Ť _EFF与增加Ť _HPT观察首次。