The so-called bimodal microstructure of Ti-6Al-4V alloy, composed of primary α grains (α_p) and transformed β areas (β_trans), can be regarded as a “dual-phase” structure to some extent, the mechanical properties of which are closely related to the sizes, volume fractions, distributions as well as nano-hardness of the two constituents. In this study, the volume fractions of primary α grains (vol.%(α_p)) were systematically modified in three series of bimodal microstructures with fixed primary α grain sizes (0.8 µm, 2.4 µm and 5.0 µm), by changing the intercritical annealing temperature (T_int). By evaluating the tensile properties at room temperature, it was found that with increasing T_int (decreasing vol.%(α_p)), the yield strength of bimodal microstructures monotonically increased, while the uniform elongation firstly increased with T_int until 910 °C and then drastically decreased afterwards, thereby dividing the T_int into two regions, namely region I (830−910 °C) and region II (910−970 °C). The detailed deformation behaviors within the two regions were studied and compared, from the perspectives of strain distribution analysis, slip system analysis as well as dislocation analysis. For bimodal microstructures in region I, due to the much lower nano-hardness of β_trans than α_p, there was a clear strain partitioning between the two constituents as well as a strain gradient from the α_p/β_trans interface to the grain interior of α_p. This activated a large number of geometrically necessary dislocations (GNDs) near the interface, mostly with <c+a> components, which contributed greatly to the extraordinary work-hardening abilities of bimodal microstructures in region I. With increasing T_int, the α_p/β_trans interface length density gradually increased and so was the density of GNDs with <c+a> components, which explained the continuous increase of uniform elongation with T_int in this region. For bimodal microstructures in region II, where the nano-hardness of β_trans and α_p were comparable, neither a clear strain-partitioning tendency nor a strain gradient across the α_p/β_trans interface was observed. Consequently, only statistically stored dislocations (SSDs) with <a> component were activated inside α_p. The absence of <c+a> dislocations together with a decreased volume fraction of α_p resulted into a dramatic loss of uniform elongation for bimodal microstructures in region II.

的Ti-6Al-4V合金的所谓双峰微结构，初级组成α晶粒（α _p）和转化的β区域（β_反式），可以被视为“双相”的结构在一定程度上，机械性能其中与两种成分的大小，体积分数，分布以及纳米硬度密切相关。在这项研究中，主要的体积分数α晶粒（体积％（α _p））的三个系列与固定主双峰微观结构进行了系统的改性α晶粒尺寸（0.8微米，2.4微米和5.0微米），通过改变两相区退火温度（T _int）。通过评估在室温下的拉伸性能，结果发现随Ť _INT（减少体积％（α _p）），双峰微结构的屈服强度单调增加，而均匀伸长率首先与增大Ť _INT直到910℃下然后随后急剧下降，从而将T _int分为两个区域，即区域I（830-910°C）和区域II（910-970°C）。从应变分布分析，滑动系统分析以及位错分析的角度研究和比较了两个区域内的详细变形行为。对于区域I中的双峰微观结构，由于纳米硬度要低得多β_反式比α _p，有两种成分之间从一个应变梯度的明确应变分区以及α _p / β_反式接口的晶粒内部α _p。这个激活的界面附近的大量几何必需位错（GND中）的，主要与< C +一>组分，其极大地促进了在区域I双峰微结构的非凡加工硬化能力随着Ť _INT时，α _p / β_反式界面长度密度逐渐增加，并且具有< c + a >分量的GND密度也逐渐增加，这解释了在该区域内T _int均匀伸长率的持续增加。在区域II双峰的微结构，其中的纳米硬度β_反式和α _p是可比的，既不是明确应变分隔倾向也不穿过一个应变梯度α _p / β_反式接口进行了观察。因此，仅存储统计学位错（SSD）的用<一>部件被内部激活α _p。< c + a的缺失的>与位错一起减小体积分数α _p导致成均匀伸长率的区域II的显着损失为双峰的微结构。